Systems and methods for testing and training vestibular and balance functions

Abstract

According to some embodiments, systems and methods are provided for testing and training vestibular and balance functions, and more specifically to multifunctional systems configured to apply perturbations to a subject via a balance measurement device and an actuator driven motion platform where the motion platform is configured to independently move in at least two directions based on at least two perturbation stimuli.

Description

Patent Application Docket No. T2024-161SYSTEMS AND METHODS FOR TESTING AND TRAINING VESTIBULAR AND BALANCE FUNCTIONSSTATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0001] This invention was made with government support under W81XWH1920003 awarded by the Congressionally Directed Medical Research Programs. The government has certain rights in the invention.CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 709,102 filed on October 18, 2024, the contents of which are incorporated herein by reference in their entirety.FIELD

[0003] The technology described herein generally relates to systems, devices, and methods for testing and training vestibular and balance functions, and more specifically to multifunctional systems for comprehensively testing and training both multidimensional vestibular functions and multidimensional balance functions.BACKGROUND

[0004] The vestibular system, a part of the inner ear, provides multidimensional information about head motion and head orientation (i.e., multiple planes of rotation, translation, and tilt). Additionally, the balance system is also a multidimensional system that adjusts in response to multidimensional perturbations experienced as we move about a complex world (e.g., slipping on ice). Despite the known multidimensional nature of both balance and vestibular function, there is currently no complete motion1204568038. vlPatent Application Docket No. T2024-161 device - for research or the clinic - that can be readily configured to provide a multidimensional assessment of vestibular function and can also be readily configured to provide a multidimensional assessment of balance function.

[0005] Accordingly, the technology described herein provides improvements over conventional techniques and systems by way of a single system and / or device that will enable a test operator to obtain both a multidimensional assay of vestibular function, as well as a multidimensional assay of balance. Importantly, accordingly to aspects of the present technology, this system can perform both assessments within a single visit, as it requires just a few minutes for the operator to reconfigure the device for balance (or vestibular) testing. Furthermore, systems and devices described herein will not require extensive construction due to its small footprint, which is small enough to fit in a standard clinical exam room.SUMMARY

[0006] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used in isolation as an aid in determining the scope of the claimed subject matter.

[0007] Embodiments of the technology described herein are generally directed toward a multifunctional system for comprehensively testing and / or training both multidimensional vestibular functions and multidimensional balance functions, and methods of using and / or implementing such systems.

[0008] According to some embodiments, a system for testing and training vestibular and balance function, comprising a six degree of freedom (6DoF) motion platform, the motion platform comprising a2204568038. vlPatent Application Docket No. T2024-161 moving platform; and six linear actuators attached to the moving platform, configured as movement axes, to drive the moving platform, wherein the moving platform is configured to move independently in one or more directions based on delivered perturbation stimuli.

[0009] According to some embodiments, a method for testing and training vestibular and balance functions, the method comprising: determining at least two balance perturbation stimuli, perturbing the balance of a subject independently in at least two directions, based on the at least two balance perturbation stimuli, and measuring at least one aspect of balance of the subject.

[0010] Additional objects, advantages, and novel features of the technology will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or can be learned by practice of the invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Aspects of the technology presented herein are described in detail below with reference to the accompanying drawing figures, wherein:

[0012] FIG. 1 illustrates RALP / LARP coordinates in the horizontal plane, in accordance with some aspects of the technology described herein;

[0013] FIG. 2A shows the displacement magnitude of example sum-of-sinusoid (SoS) trajectories at individual perturbation frequencies, in accordance with some aspects of the technology described herein;

[0014] FIG. 2 B shows the velocity magnitude of example sum-of-sinusoid (SoS) trajectories at individual perturbation frequencies, in accordance with some aspects of the technology described herein;

[0015] FIG. 3A shows plots illustrating the distribution of RMSD across 24 subjects based on various tested conditions, in accordance with some aspects of the technology described herein;3204568038. vlPatent Application Docket No. T2024-161

[0016] FIG. 3B shows plots illustrating the distribution of mean velocity across 24 subjects based on various tested conditions, in accordance with some aspects of the technology described herein;

[0017] FIG. 4A shows a power spectra plot of the average magnitude of the spectral response ofCoP in the ML plane across test subjects, when tilt stimuli were applied in roll and pitch, in accordance with some aspects of the technology described herein;

[0018] FIG. 4B shows a power spectra plot of the average magnitude of the spectral response of CoP in the AP plane across test subjects, when tilt stimuli were applied in roll and pitch, in accordance with some aspects of the technology described herein;

[0019] FIG. 4C shows a power spectra plot of the average magnitude of the spectral response of CoP in the RALP plane across test subjects, when tilt stimuli were applied in roll and pitch, in accordance with some aspects of the technology described herein;

[0020] FIG. 4D shows a power spectra plot of the average magnitude of the spectral response of CoP in the LARP plane across test subjects, when tilt stimuli were applied in roll and pitch, in accordance with some aspects of the technology described herein;

[0021] FIG. 5A shows a power spectra plot of the average magnitude of the spectral response of CoP in the ML plane across test subjects, when tilt stimuli were applied in RALP and LARP planes, in accordance with some aspects of the technology described herein;

[0022] FIG. 5B shows a power spectra plot of the average magnitude of the spectral response of CoP in the AP plane across test subjects, when tilt stimuli were applied in RALP and LARP planes, in accordance with some aspects of the technology described herein;

[0023] FIG. 5C shows a power spectra plot of the average magnitude of the spectral response of CoP in the RALP plane across test subjects, when tilt stimuli were applied in RALP and LARP planes, in accordance with some aspects of the technology described herein;4204568038. vlPatent Application Docket No. T2024-161

[0024] FIG. 5D shows a power spectra plot of the average magnitude of the spectral response of CoP in the LARP plane across test subjects, when tilt stimuli were applied in RALP and LARP planes, in accordance with some aspects of the technology described herein;

[0025] FIG. 6A shows a power spectra plot of the average magnitude of the spectral response of CoP in the ML plane across test subjects, when tilt stimuli were applied in roll and pitch as well as RALP and LARP planes, in accordance with some aspects of the technology described herein;

[0026] FIG. 6B shows a power spectra plot of the average magnitude of the spectral response of CoP in the AP plane across test subjects, when tilt stimuli were applied in roll and pitch as well as RALP and LARP planes, in accordance with some aspects of the technology described herein;

[0027] FIG. 6C shows a power spectra plot of the average magnitude of the spectral response of CoP in the RALP plane across test subjects, when tilt stimuli were applied in roll and pitch as well as RALP and LARP planes, in accordance with some aspects of the technology described herein;

[0028] FIG. 6D shows a power spectra plot of the average magnitude of the spectral response of CoP in the LARP plane across test subjects, when tilt stimuli were applied in roll and pitch as well as RALP and LARP planes, in accordance with some aspects of the technology described herein;

[0029] FIG. 7A show the sensitivity (left y-axis) and phase (right y-axis) of the CoP response in the ML plane versus perturbation stimulus frequency, in accordance with some aspects of the technology described herein;

[0030] FIG. 7B show the sensitivity (left y-axis) and phase (right y-axis) of the CoP response in the AP plane versus perturbation stimulus frequency, in accordance with some aspects of the technology described herein;204568038. vlPatent Application Docket No. T2024-161

[0031] FIG. 7C show the sensitivity (left y-axis) and phase (right y-axis) of the CoP response in theRALP plane versus perturbation stimulus frequency, in accordance with some aspects of the technology described herein;

[0032] FIG. 7D show the sensitivity (left y-axis) and phase (right y-axis) of the CoP response in the LARP plane versus perturbation stimulus frequency, in accordance with some aspects of the technology described herein;

[0033] FIG. 8A show the sensitivity (left y-axis) and phase (right y-axis) of the CoP response in the ML plane versus perturbation stimulus frequency, in accordance with some aspects of the technology described herein;

[0034] FIG. 8B show the sensitivity (left y-axis) and phase (right y-axis) of the CoP response in the AP plane versus perturbation stimulus frequency, in accordance with some aspects of the technology described herein;

[0035] FIG. 8C show the sensitivity (left y-axis) and phase (right y-axis) of the CoP response in the RALP plane versus perturbation stimulus frequency, in accordance with some aspects of the technology described herein;

[0036] FIG. 8D show the sensitivity (left y-axis) and phase (right y-axis) of the CoP response in the LARP plane versus perturbation stimulus frequency, in accordance with some aspects of the technology described herein

[0037] FIG. 9A shows average frequency response functions of CoP ML in the complex plane across the 24 subjects when simultaneous roll / pitch / RALP / LARP stimuli were provided;

[0038] FIG. 9B shows average frequency response functions of CoP ML in the complex plane across the 24 subjects when roll / pitch stimuli were provided on separate trials than RALP / LARP stimuli;6204568038. vlPatent Application Docket No. T2024-161

[0039] FIG. 9C shows average frequency response functions of CoP AP in the complex plane across the 24 subjects when simultaneous roll / pitch / RALP / LARP stimuli were provided

[0040] FIG. 9D shows average frequency response functions of CoP AP in the complex plane across the 24 subjects when roll / pitch stimuli were provided on separate trials than RALP / LARP stimuli;

[0041] FIG. 9E shows average frequency response functions of CoP RALP in the complex plane across the 24 subjects when simultaneous roll / pitch / RALP / LARP stimuli were provided;

[0042] FIG. 9F shows average frequency response functions of CoP RALP in the complex plane across the 24 subjects when roll / pitch stimuli were provided on separate trials than RALP / LARP stimuli;

[0043] FIG. 9G shows average frequency response functions of CoP LARP in the complex plane across the 24 subjects when simultaneous roll / pitch / RALP / LARP stimuli were provided;

[0044] FIG. 9H shows average frequency response functions of CoP LARP in the complex plane across the 24 subjects when roll / pitch stimuli were provided on separate trials than RALP / LARP stimuli;

[0045] FIG. 10A shows average frequency response functions of CoP ML in the complex plane across the 24 subjects when simultaneous roll / pitch / RALP / LARP stimuli were provided;

[0046] FIG. 10B shows average frequency response functions of CoP ML in the complex plane across the 24 subjects when roll / pitch stimuli were provided on separate trials than RALP / LARP stimuli;

[0047] FIG. 10C shows average frequency response functions of CoP AP in the complex plane across the 24 subjects when simultaneous roll / pitch / RALP / LARP stimuli were provided;

[0048] FIG. 10D shows average frequency response functions of CoP AP in the complex plane across the 24 subjects when roll / pitch stimuli were provided on separate trials than RALP / LARP stimuli;

[0049] FIG. 10E shows average frequency response functions of CoP RALP in the complex plane across the 24 subjects when simultaneous roll / pitch / RALP / LARP stimuli were provided;7204568038. vlPatent Application Docket No. T2024-161

[0050] FIG. 10F shows average frequency response functions of CoP RALP in the complex plane across the 24 subjects when roll / pitch stimuli were provided on separate trials than RALP / LARP stimuli;

[0051] FIG. 10G shows average frequency response functions of CoP LARP in the complex plane across the 24 subjects when simultaneous roll / pitch / RALP / LARP stimuli were provided;

[0052] FIG. 10H shows average frequency response functions of CoP LARP in the complex plane across the 24 subjects when roll / pitch stimuli were provided on separate trials than RALP / LARP stimuli;

[0053] FIG. 11 illustrates an example 6DoF balance and vestibular threshold assessment and / or training device, in accordance with some aspects of the technology described herein; and

[0054] FIG. 12 is a diagram of an example computing environment suitable for use in implementing embodiments of the present technology.DETAILED DESCRIPTION

[0055] The subject matter of aspects of the present disclosure is described with specificity herein to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different steps or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies. Moreover, although the terms “step” and / or “block” can be used herein to connote different elements of methods employed, the terms should not be interpreted as implying any particular order among or between various steps disclosed herein unless and except when the order of individual steps is explicitly described.

[0056] Accordingly, embodiments described herein can be understood more readily by reference to the following detailed description, examples, and figures. Elements, apparatus, and methods described herein, however, are not limited to the specific embodiments presented in the detailed description,8204568038. vlPatent Application Docket No. T2024-161 examples, and figures. Tt should be recognized that the exemplary embodiments herein are merely illustrative of the principles of the invention. Numerous modifications and adaptations will be readily apparent to those of skill in the art without departing from the spirit and scope of the invention.

[0057] In addition, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of “1.0 to 10.0” should be considered to include any and all subranges beginning with a minimum value of 1.0 or more and ending with a maximum value of 10.0 or less, e.g., 1.0 to 5.3, or 4.7 to 10.0, or 3.6 to 7.9.

[0058] All ranges disclosed herein are also to be considered to include the end points of the range, unless expressly stated otherwise. For example, a range of “between 5 and 10” or “5 to 10” or “5-10” should generally be considered to include the end points 5 and 10.

[0059] Further, when the phrase “up to” is used in connection with an amount or quantity; it is to be understood that the amount is at least a detectable amount or quantity. For example, a material present in an amount “up to” a specified amount can be present from a detectable amount and up to and including the specified amount.

[0060] Additionally, in any disclosed embodiment, the terms “substantially,” “approximately,” and “about” may be substituted with “within [a percentage] of’ what is specified, where the percentage includes 0.1, 1, 5, and 10 percent.

[0061] Disjunctive language such as the phrase “at least one of X, Y, or Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to present that an item, term, etc., may be either X, Y, or Z, or any combination thereof (e.g., X, Y, and / or Z). Thus, such disjunctive204568038. vlPatent Application Docket No. T2024-161 language is not generally intended to, and should not, imply that certain embodiments require at least one of X, at least one of Y, or at least one of Z to each be present.

[0062] Existing clinical vestibular assessment devices. Clinical devices used to assess the vestibular system, consisting of three semicircular canals and two otoliths in each ear, focus primarily upon quantification of vestibular mediated reflexes, including the vestibulo-ocular reflex (VOR) via the measurement of eye motion, otolith mediated oculomotor and cervical spine reflexes via vestibular evoked myogenic potentials (VEMPs), and the vestibulo-spinal reflexes (VSR) via measurement of postural sway. To comprehensively assay each vestibular reflex, several different clinical testing systems must be used. The VOR is quantified by measuring the oculomotor response during (1) caloric irrigation which stimulates vestibular responses via the introduction of a temperature gradient across the endolymph in the inner ear, (2) rotational chair testing which uses whole body rotations to measure the corresponding eye velocity response, or (3) video head impulse testing (vHIT) which measures eye velocity in response to rapid, unpredictable head on body rotations. However, only one of these tests, vHIT, is able to extend the analysis to quantify the vertical semicircular canals, with caloric irrigation and rotational chair testing providing measures restricted to the lateral semicircular canals. Conversely, to quantify the otolith organs, a separate evoked potential unit is required to measure VEMPs. VEMPs use electromyography to detect changes in the oculomotor and cervical musculature in response to stimulation of the otolith afferents via sound or vibration stimuli. Finally, to coarsely summarize descending vestibulospinal function, a sophisticated balance platform with a moving support surface (e.g., sensory organization test) is needed. However, these commercially available balance platforms are typically only capable of moving the support surface in one degree of freedom (IDoF). The two most common systems can only perform IDoF fore-aft tilts or IDoF fore-aft translations, whereas a third10204568038. vlPatent Application Docket No. T2024-161 system is capable of providing support surface movement in 3DoF (i.e., up-down translation, fore-aft tilt, and mediolateral tilt).

[0063] As a result, to quantify all aspects of vestibular function (i.e., all three semicircular canals, as well as the two otolith organs, in each ear) a minimum of two clinical test systems is needed. Yet, even if these different systems are available to the clinician or researcher, each test device uses disparate methodologies to indirectly assay the integrity of the semicircular canals (via the VOR stimulated by motion or thermal stimuli) and the otoliths (via VEMPs stimulated by sound or vibration). As a further limitation, these assessments are all completed in a sitting position, and fail to provide a measure of descending contributions of the vestibular system to postural control.

[0064] Conversely, devices dedicated to the assessment of balance are too coarse to provide granular information that discerns the relative function of the different vestibular modalities. Ultimately, to measure the three semicircular canals, the two otolith organs, and postural control, a total of (at least) three clinical systems would be needed.

[0065] Due to these limitations, no single clinical device is capable of providing a comprehensive battery of tests that can fully capture vestibular function and fully characterize all dimensions of postural control. Due to each of the unique test devices probing different downstream sensorimotor responses (e.g., VOR vs. postural sway vs. EMG activity at the neck), relative comparisons between different vestibular modalities is fundamentally hindered by confounding factors that are unique to each of the three assessments. Moreover, each of the available clinical test devices use exclusively sensorimotor responses to infer the integrity of vestibular sensory function; as such, the motor limb, and / or sensorimotor transformation, is inherently tested in each test paradigm.

[0066] Ultimately with conventional systems, clinicians are unable to discern the relative effects of aging or pathology on different elements of the vestibular periphery. This has created a substantive11204568038. vlPatent Application Docket No. T2024-161 knowledge gap which has limited targeted therapeutic interventions that are tailored to address the dysfunction of individual vestibular modalities.

[0067] Existing research-based vestibular assessment devices. In several research laboratories across the world, six degree of freedom (6D0F) motion platforms have been utilized to quantify vestibular thresholds. Vestibular thresholds quantify the smallest motion stimulus that a human can reliability perceive. The use of a 6D0F platform permits the assessment of self-motion cues along the planes of motion whereby the different vestibular end organs are preferentially stimulated. This includes yaw rotations to stimulate the lateral semicircular canals, interaural translations to stimulate the utricles, and cranio-caudal translations to stimulate the saccules. Rotations performed along the orthogonally orientated anterior and posterior vertical canal pairs — right anterior with left posterior (RALP) and left anterior with right posterior (LARP) — are performed to assay the vertical semicircular canals. Thus, unlike the multiple indirect sensorimotor measures used to quantify the different end organs (canals via the VOR and otoliths via VEMPs), perceptual thresholds use a single methodology — a perceptual direction recognition task — to measure the integrity of each aspect of the vestibular periphery. In addition, more complex multidimensional motion paradigms (e.g., head centered roll tilts, perception of curved motion) can be used to assay the central integration of canal and otolith inputs, a function neglected by clinical vestibular testing devices.

[0068] Nearly all of these vestibular research (i.e., non-commercial) systems employ several common elements that include (1) a hexapod motion platform capable of performing controlled motion in each of the 6DoF, (2) a chair rigidly mounted to the platform to secure the participant, (3) a head restraint to control head orientation relative to the motion stimulus, (4) software used to control the12204568038. vlPatent Application Docket No. T2024-161 motion platform and to record subject responses, and (5) a mechanism to record subject responses indicating motion perception.

[0069] However, there is no conventional device or testing protocol that can both measure postural control (via the use of force plates, inertial measurement units, or motion capture) with the coordinate system origin near the ankle while also providing the ability to also measure 6D0F of vestibular thresholds in a seated position with head located near the coordinate system origin (to minimize headtranslation coupled with rotations). Thus, even laboratories with a 6D0F platform capable of measuring vestibular thresholds, require a second device to measure descending vestibular function via the quantification of human postural sway.

[0070] Existing balance assessment systems. Existing commercial balance platforms include between IDoF (e.g., NeuroCom and Bertec CDP / IVR) and 3DoF (Virtualis Motion VR) of platform motion. Some available IDoF platforms also have the capability to perform a second DoF (fore-aft translation), yet the fore-aft motion is (1) transient (rather than continuous) and (2) cannot be combined with fore-aft tilts of the platform. As a result, such systems can only deliver a IDoF motion stimulus. Each of these existing systems possess a footprint, and cost, that is suitable for most clinical settings, however none of the available devices can (1) deliver more than 3DoF of motion or (2) be modified to permit the comprehensive assessment of vestibular thresholds. While, in theory, a chair and accompanying hardware (e.g., helmet, response buttons) could be added to these devices, their constraint to 3DoF or less provides a substantial barrier to their use in the quantification of vestibular thresholds, which require 6DoF to fully characterize vestibular function. Other barriers include a lack of data to13204568038. vlPatent Application Docket No. T2024-161 support that such devices are capable of sufficient precision to provide threshold level stimuli with the added weight of the necessary threshold assessment equipment (e.g., chair, helmet).

[0071] A select few research laboratories have purchased a commercial research system that is capable of providing 6D0F balance (as well as gait) perturbations and measuring the corresponding postural sway. Few systems could potentially provide such capability but complexity and large footprint of such devices precludes its use in nearly all clinical settings. Moreover, no one has modified such device to permit the assessment of vestibular thresholds. This is both a hardware issue — due to the need to mount a chair where the split belt treadmill is located centrally on the motion platform — as well as a software issue — as custom software used to quantify vestibular thresholds has not been implemented. In addition to these primary limitations, the cost of devices (upwards of $1,000,000) and the complexity of managing the software, yields substantial barriers to widespread clinical implementation.

[0072] Embodiments of the technology described herein are generally directed toward a multifunctional system for comprehensively testing and / or training both multidimensional vestibular functions and multidimensional balance functions, and methods of using and / or implementing such systems. According to some aspects, a single system (clinical and / or research) is provided that is capable of (1) quantifying both the otolith organs (saccule and utricle), as well as the three semicircular canals (anterior, posterior, and lateral) using a single methodology (i.e., vestibular thresholds), (2) being easily modified to permit the assessment of postural control in conditions that range from quiet stance, to 6DoF pseudorandom balance perturbations, (3) providing multidimensional balance training to reduce fall risk and to enhance balance stability, (4) providing vestibular training to enhance vestibular function to increase stability and reduce fall risk, and (5) providing each of these functions while maintaining a14204568038. vlPatent Application Docket No. T2024-161 sufficiently small footprint (for example, approximately 10’ x 10’ x 8’), and cost, to allow the use in clinical settings.

[0073] According to some aspects, a motion platform is provided, for example a 6 degree of freedom (6DoF) motion platform. The motion platform (e.g. motion platform 100 of FIG. 11) can include one or more linear actuators, for example 6 linear actuators (e.g. actuators 102 of FIG. 11) attached to a moving platform (e.g. moving platform 104 of FIG. 11). In some embodiments, a motion platform can comprise one or more additional components, such as safety barrier 106, chair / seat 108, adjustable helmet 110 and / or forceplate 112. According to some aspects, the motion platform and any additional components can be configured for either balance testing and / or training or vestibular testing and / or training. In some example embodiments, the system (e.g. multifunctional system) can further comprise rails to slide and / or move the chair into a vestibular test configuration or into a balance test configuration. In some aspects, a motion platform can deliver stimuli (e.g. tilt stimuli) in one or more directions, for instance up to eight directions reflecting positive and negative motions in each of four dimensions, for example the pitch plane, the roll plane, and planes that intersect roll and pitch at orthogonal angles, LARP and RALP planes.

[0074] At the distal end of each actuator can be a joint, such as a ball joint, which provides the necessary motion to permit 6DoF platform motion. This includes 3DoF of translation (mediolateral, fore-aft, and cranio-caudal), and 3DoF of rotation / tilt about each of these axes (roll, pitch, and yaw). In some example embodiments, the device can have a maximum displacement limit of 19 cm of translation. In some example embodiments, the device can have a displacement limit of 20 degrees of tilt / rotation. As will be appreciated, the device can have any displacement limits not inconsistent with the objectives of the present technology. Across any range of displacements, a targeted precision of ±15204568038. vlPatent Application Docket No. T2024-1610.5% of the input stimulus can be targeted or achieved. Tn addition to motion in each of the 6D0F, the platform can be capable of multi-axis motions that combine any of the 6D0F of platform motion.

[0075] The payload design (e.g. FIG. 11) can enable the measurement of seated vestibular thresholds as well as the assessment of postural control with a human subject in a standing orientation. Seated vestibular thresholds can be measured by securely mounting a seat to the platform, with a helmet positioned over the centroid of the device to secure the orientation of the head during testing. A five- point harness can be used for safety and to help control orientation of the body while in motion.Vestibular thresholds can be measured by having the individual use response buttons (or another manipulator such as a joystick, tablet, smartphone) to indicate their perception of the motion direction. Automated software can dictate the size and direction of the motion stimuli delivered by the motion platform. Additional considerations include the use of a sound box to control the delivery of sound stimuli during motion (both to cue the subject as well as to mask auditory feedback from the room), as well as to provide feedback during different perceptual training interventions. As will be appreciated, the improvements in the underlying technology come from, in part, modifications to hardware and software designs that permit or enable the measurement of seated and / or standing postural sway using the same motion device.

[0076] Some additional elements in some embodiments can include one or more of: (1) The chair will be mounted on linear rails that allow the chair to be moved away from the centroid of the motion platform (e.g., posteriorly). (2) The force plate is secured so that the top of the force plate is at or even many centimeters below the surface of the moving platform. (3) After locking the chair in place away from the motion centroid, the force plate(s) will then be accessible for a participant to stand on. Once the chair is displaced posteriorly, balance can be tested by having the subject stand within the safety rails during motion of the platform; removable safety rails can be mounted for safety (e.g. FIG. 1).16204568038. vlPatent Application Docket No. T2024-161Accordingly, balance can be measured via the force plates, as well as with the use of motion capture devices, mounted in the room surrounding the platform, and / or inertial measurement units, positioned on a subject’s body. In some example embodiments the motion capture device can be implemented as one or more cameras.

[0077] According to some aspects, systems and methods can include one or more software features, modules, engines, and / or components. For example, vestibular threshold and balance assessments can be carried out using a graphical user interface (GUI) that can allow or enable for the assessment of both vestibular thresholds, as well as several different balance assessments. The GUI can allow a user to select vestibular threshold protocols, and balance protocols that are developed, stored, and can be called by the system.

[0078] Vestibular threshold protocols can be delivered along any of the 6D0F of motion, as well as during combined multi-DoF motion. Through the GUI, users can select the DoF of interest (or one or more DoF), as well as the parameters of the motion stimulus (e.g., frequency, initial velocity). These tests include for example, IDoF direction recognition tasks (“did you move right or left”), as well as more complex N-DoF tasks, whereby the subject is prompted to choose from N=12 (or more) different response options.

[0079] Balance test paradigms can include pseudorandom perturbations of the platform delivered in multiple DoF simultaneously; this is accomplished through systems and methods whereby unique sum of sinusoids signals are generated for each DoF of motion. In addition, the systems and devices can be able to carry out existing clinical balance assessments such as the Sensory Organization Test (SOT) by17204568038. vlPatent Application Docket No. T2024-161 using the 6D0F motion platform to sway reference the support surface (i.e., move the platform in response to the participants sway), according to real-time data acquired from the attached force plate.

[0080] Training protocols. Aside from the use of the device to measure vestibular and balance function, the same capabilities of the platform permit the device to be used to deliver training interventions that target improvements in both vestibular, as well as balance, function. Specific interventions include (1) vestibular perceptual training, where subjects are asked to report their perception of vestibular motion and are given feedback on their accuracy, (2) multidimensional perturbed stance balance training where subjects are asked to remain upright when exposed to various IDoF to 6DoF balance perturbations.

[0081] Embodiments of the invention can be described in the context of computer code or machine-useable instructions, including computer-executable instructions such as program modules, being executed by a computer or other machine (virtual or otherwise), such as a smartphone or other handheld device. Generally, program modules, or engines, including routines, programs, objects, components, data structures etc., refer to code that perform particular tasks or implement particular abstract data types. Embodiments of the invention can be practiced in a variety of system configurations, including hand-held devices, consumer electronics, general-purpose computers, more specialized computing devices, etc. Embodiments of the invention can also be practiced in distributed computing environments where tasks are performed by remote-processing devices that are linked through a communications network.

[0082] With reference to FIG. 12, computing device 2000 includes a bus 2010 that directly or indirectly couples the following devices: memory 2012, one or more processors 2014, one or more presentation components 2016, input / output ports 2018, input / output components 2020, an illustrative power supply 2022, and one or more radios 2024. In some embodiments, devices described herein18204568038. vlPatent Application Docket No. T2024-161 utilize wired and rechargeable batteries and power supplies. Bus 2010 represents what can be one or more busses (such as an address bus, data bus or combination thereof). Although the various blocks of FIG. 20 are shown with clearly delineated lines for the sake of clarity, in reality, such delineations are not so clear and these lines can overlap. For example, one can consider a presentation component such as a display device to be an I / O component as well. Also, processors generally have memory in the form of cache. It is recognized that such is the nature of the art, and reiterate that the diagram of FIG. 20 is merely illustrative of an example computing device that can be used in connection with one or more embodiments of the present disclosure. Distinction is not made between such categories as “workstation,” “server,” “laptop,” “hand-held device,” etc., as all are contemplated within the scope of Fig. 12 and reference to “computing device.”

[0083] Computing device 2000 typically includes a variety of computer-readable media. Computer- readable media can be any available media that can be accessed by computing device 2000, and includes both volatile and non-volatile media, removable and non-removable media. By way of example, and not limitation, computer-readable media can comprise computer storage media and communication media.

[0084] Computer storage media include volatile and non-volatile, removable and non- removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by computing device 2000. Computer storage media excludes signals per se.19204568038. vlPatent Application Docket No. T2024-161

[0085] Communication media typically embodies computer-readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term "modulated data signal" means a signal that has one or more of its characteristics set or changed in such a manner at to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared, NFC, Bluetooth and other wireless media. Combinations of any of the above should also be included within the scope of computer-readable media.

[0086] Memory 2012 includes computer storage media in the form of volatile and / or non-volatile memory. As depicted, memory 2012 includes instructions that when executed by processor(s) 1014 are configured to cause the computing device to perform any of the operations described herein, in reference to the above discussed figures, or to implement any program modules described herein. The memory can be removable, non-removable, or a combination thereof. Illustrative hardware devices include solid-state memory, hard drives, optical-disc drives, etc. Computing device 2000 includes one or more processors that read data from various entities such as memory 2012 or I / O components 2020. Presentation component(s) 2016 present data indications to a user or other device. Illustrative presentation components include a display device, speaker, printing component, vibrating component, etc.

[0087] I / O ports 2018 allow computing device 2000 to be logically coupled to other devices including I / O components 2020, some of which can be built in. Illustrative components include a microphonejoystick, game pad, satellite dish, scanner, printer, wireless device, battery, etc.

[0088] In some aspects, systems described herein can be implemented to include, among other components, a motion platform or vestibular threshold assessment and / or training device, a data source and / or repository, a user device or input device, and a stimulus engine. These and other components can20204568038. vlPatent Application Docket No. T2024-161 be configured to be in operable communication with one another via one or more remote or local network(s). The network can be further connected to one or more local or remote servers or other computing systems, for example portable computing systems such as a tablet or smartphone.

[0089] A measurement and / or assessment system and / or training device can comprise one or more engines, modules, and / or components, to carry out operations associated with the balance and / or gait perturbation and measurement system, such as those operations described herein. In some embodiments, a system comprises a stimulus engine which can incorporate one or more components and / or modules that can generate one or more perturbation trajectories and operate to control motion platform. As will be appreciated, the configuration of the system is not limited and can be implemented where a stimulus engine operates as a part of a distributed system (e.g. on a server), or can be configured to run on user device, or can be integrated with motion platform. In some aspects, stimulus engine can communicate with data source to for example, call one or more datasets and / or algorithms for use in operations, or further, stimulus engine can store generated data (e.g. generated perturbation time trajectories) or subject data, cohort data, study data (or for instance user profiles) on data source / repository.

[0090] Input selection component is generally responsible for receiving one or more inputs from user device. For example, the one or more inputs can include, but are not limited to, a selected frequency or multiple selected frequencies (e.g. a fundamental frequency) and / or one or more number sets (e.g. interleaved prime numbers). In some instances, the frequency and or numbers in a number set can be randomly selected or can be based on determined / predetermined criteria. Stimuli trajectory component can receive one or more inputs from input and / or selection component and generate or determine one or more perturbation time trajectories (e.g. SoS displacement and / or perturbation time trajectories). In some instances, Stimuli trajectory component can comprise one or more modules, for example, frequency component module and sinusoidal response summation module. In some aspects, frequency21204568038. vlPatent Application Docket No. T2024-161 component module can generate one or more frequency components based on the input(s) and sinusoidal response summation module can generate or determine one or more SoS trajectories (i.e. motion and / or time trajectories) by summing up sinusoidal responses based on the one or more frequency components (or spectra). Perturbation component can subsequently perturb motion platform based on the SoS trajectories (e.g. SoS motion / time trajectories utilized as inputs to perturb the motion platform), where the determined SoS trajectories are implemented as signals for motion control.EXAMPLES

[0091] External continuous perturbations using a motion platform have been developed by way of the present technology by employing either sum-of-sines (SoS) or a pseudorandom ternary sequence (PRTS) of numbers to quantify ML (Medial-Lateral) or AP (Anterior-Posterior)-evoked body sway, which ultimately improves understanding of the human multidimensional postural control system. These stimuli have been provided via pitch tilts of the motion platform for evaluations of AP balance responses or roll tilts for ML balance responses. However, little is known about whether a healthy postural control system responds to 2-dimensional (2D) perturbations similarly when the perturbation stimuli are provided in roll / pitch coordinates versus semicircular canal coordinates, (i.e., Right-Anterior / Left- Posterior (RALP) and Left-Anterior / Right-Posterior (LARP)). 2D platform perturbations provided in RALP / LARP coordinates have potential to better assess the contribution of each pair of the vertical semicircular canals to postural control for individuals with vestibular dysfunction. Four unique balance perturbation trajectories were developed using SoS signals and simultaneously provided those stimuli in (i) roll and pitch, (ii) RALP and LARP, and (iii) roll, pitch, RALP, and LARP dimensions. Center of Pressure (CoP) data were collected from 24 healthy participants (40±13 years of age) on a commercially available motion platform (Virtualis Motion VR, Perault, France). It was found that ML and AP postural22204568038. vlPatent Application Docket No. T2024-161 responses were not significantly different when the platform perturbations were simultaneously provided in roll / pitch coordinates versus RALP / LARP coordinates that are orthogonal in both time and space. This finding suggests that 2D platform perturbations in RALP / LARP coordinates allow (1) comparison of ML and AP responses evoked by RALP and LARP stimuli to existing literature showing those responses evoked by roll and pitch stimuli and (2) to characterize postural responses for individuals with sensory deficits to assess contributions of the vertical semicircular canals to postural control.

[0092] Methods

[0093] Generation of Sum-of-Sines (SoS) Signals. SoS signals were delivered to perturb balance simultaneously in the roll and pitch directions during Condition (i), simultaneously in the RALP and LARP directions during Condition (ii), and in the roll, pitch, RALP and LARP directions simultaneously during Condition (iii). The roll and pitch signals were orthogonal to one another in both time and space. Similarly, the RALP and LARP signals were also orthogonal to one another in time and space. During Condition (iii), the roll, pitch, RALP and LARP stimuli were each orthogonal in time to all other stimuli, but roll and pitch stimuli were, by definition, not spatially orthogonal to the RALP and LARP stimuli.

[0094] In some aspects, two simultaneous SoS perturbations may be generated (e.g. orthogonal to each other in the time domain and / or separable in the frequency domain). Here, four distinct SoS balance perturbation trajectories are developed that could be provided simultaneously during Condition (iii) as the stimuli for roll, pitch, RALP, and LARP. The trajectories used a fundamental frequency of 0.0055 Hz multiplied by four groups of interleaved multipliers ([11,59,109,179,241], [13,61,113,181,251], [15,71,131,193,263], and [17,67,127,191,257]). No multipliers were repeated; each multiplier, except 15, was a prime number. Neither of 15’ s prime factors (3 or 5) was used; this avoids overlapping at higher harmonics, (e.g., 3rdharmonic associated with the multiplier 5). Each frequency component was orthogonal in time to all other frequency components. Each of these SoS23204568038. vlPatent Application Docket No. T2024-161 trajectories was named to reflect the lowest multiplier (i.e., S0S11, S0S13, S0S15, and S0S17). When multiplied by the fundamental frequency, these integer sets yielded the following four frequency sets: fsosn = [0.0604, 0.3241, 0.5988, 0.9833, 1.3239] Hz fsosi3 = [0.0714, 0.3351, 0.6207, 0.9943, 1.3788] Hz fsosis = [0.0824, 0.3900, 0.7196, 1.0602, 1.4447] Hz fsoS17 = [0.0934, 0.3680, 0.6976, 1.0492, 1.4117] Hz

[0095] The four steady-state SoS displacement trajectories were generated by summing sinusoidal signals. For example, the following equation was used to generate the S0S11 trajectory:

[0096] In this equation, t represents time, All tis the ithamplitude, fi iis the ithfrequency, and 0n i is the ithphase value. These equations resulted in four SoS trajectories having interleaved, spectrally separated perturbation frequencies.

[0097] The phase values were determined via a systematic search using one-degree phase increments between 0 and 359° to minimize differences in the peak-to-peak amplitude of the four trajectories while keeping the velocity spectral magnitude constant across all frequencies (Table 1). The magnitude was scaled so that S0S13 had a peak-to-peak amplitude of 1 deg. This yielded a 0.177s spectral velocity magnitude for each of the 5 frequency components. For the other trajectories, the magnitude of each spectral velocity component constant across all perturbation frequencies was maintained. This yielded peak-to-peak displacement amplitudes of 1.1051 deg for the S0S11 signal, 0.9592 deg for the S0S15 signal, and 0.8948 deg for the S0S17 signal. These four trajectories each had the exact same velocity magnitude of 0.17 deg / s at each of their five disturbance frequencies (Figure 2B).

[0098] The signals were shifted in time to begin motion at a displacement zero-crossing to minimize transients that otherwise might unduly perturb subjects at the beginning of the trial. Table 1 shows the24204568038. vlPatent Application Docket No. T2024-161 original phase as well as the shifted phase values of S0S11, S0S13, S0S15, and S0S17 at each individual frequency.

[0099] A commercially available device (Virtualis Motion VR, Perault, France) was used to provide the platform tilt perturbations. The steady-state perturbation was designed to have a duration of 182.0444s yielded by 16,384 (214) points at the Virtualis platform’s sampling / refresh rate of 90 Hz. To allow the postural response to reach steady-state prior to the start of this steady-state cycle, 20s of stimuli identical to the last 20s of the steady state waveforms were added before the steady state waveform. A 0.2s ramp-up phase before the 20s steady state waveforms was also added to minimize sudden motions that could potentially disturb our subjects or their responses. Since the steady-state cycle was repeated just once, the total perturbation duration was 202.2444s for all trials.

[0100] The frequency, magnitude, and phase used to create each of the SoS time series are shown in Table 1. 0Orepresents the original phase value used to create the SoS signals. 0Srepresents the shifted phase value calculated from the actual signal following a time-shift to start the steady-state of each of the SoS trajectories at a position zero-crossing.Table 125204568038. vlPatent Application Docket No. T2024-161

[0101] Test Procedures. Postural response data from 24 healthy participants was collected. A custom script written in Matlab first generated the SoS time series and the resultant CSV files were imported into the Virtualis Motion VR Research software to deliver platform perturbations. Center of pressure (CoP) data were collected by two embedded force plates at a sampling rate of 90Hz.

[0102] All of the participants completed 6 trials per day on each of two separate days - yielding 12 trials in total for each subject (Table 2). The two test days were separated by more than 1 day but less than 18 days. All but one participant completed the testing within 9 days. The order of the 12 trials was randomized to mitigate order effects. Participants’ feet were bare, with the outside edge of feet separated by 28 cm. Arms were crossed with hands on shoulders. Participants were asked to close their eyes. Participants wore a virtual reality headset (HTC VIVE) that showed a dark screen to eliminate visual cues if a participant opened their eyes. Prior to testing, participants were instructed to stand as still as possible without any extra motions or verbal responses. Each participant was asked to rest at least one26204568038. vlPatent Application Docket No. T2024-161 minute between trials to minimize fatigue. Table 2 shows the SoS trajectories selected for motion stimuli in each trial.Table 2 roll pitch RALP LARP

[0103] Particpants. Prior to testing, all participants provided their written informed consent to participate in the study. Twenty-four healthy participants including 12 males and 12 females participated in the study. The age range of the participants was 21-65 yr (40.3± 13.1 years). To qualify as a healthy normal participant, strict criteria intended to eliminate conditions that might affect normal vestibular function or standing balance were assessed by a health questionnaire as a part of a central registry. These exclusion criteria included neurological disorders such as neurodegenerative disease, peripheral neuropathy, epilepsy, traumatic brain injury, or prior stroke; active vestibular disorders such as vestibular migraine, persistent postural-positional dizziness, Meniere disease, prior acute vestibular syndrome with peripheral vestibular loss, vestibular areflexia, or unresolved benign paroxysmal positional vertigo; orthopedic impairments affecting standing such as orthopedic injuries or impairments204568038. vlPatent Application Docket No. T2024-161 of the lower extremities; and active ongoing medical conditions (recent surgery, severe heart disease or pulmonary disease, and cancer).

[0104] Postural Analyses. CoP data was analyzed using custom Matlab scripts. The first 20s of data for each trial were eliminated to remove the transient response at the onset of the perturbation. Each remaining CoP signal, having 16,384 data points representing 182.044 s was shifted to have zero mean and filtered using a zero-phase 2ndorder Butterworth low-pass filter with a cut-off frequency of 20Hz.

[0105] To estimate RALP and LARP CoP sway, ML and AP CoP were rotated 45 degrees clockwise using the following equations:C°PLARP (0 _ rcos 45° — sin 45°l C°PML (0FOPRALP (f). in 45° cos 45° J CoPAp (t).

[0106] A discrete Fourier transform (Matlab, fft.m) was applied to ML, AP, RALP, and LARP CoP signals and to roll, pitch, RALP and LARP perturbation signals. The complex numbers resulting from the discrete Fourier transform (DFT) were divided by the length of the data points (N = 16,384). The first half of the two-sided spectrum was removed, and the positive spectrum was multiplied by 2 to convert each two-sided amplitude spectrum to a single-sided amplitude spectrum. Frequency response functions (FRF) were used to describe the sensitivity and phase of the CoP response relative to the tilt perturbation as a function of frequency. The FRF values are determined by dividing the complex DFT of the CoP by the complex DFT of the platform tilt angles (SoSlltSoS13, SoS15, and SoSl7) at each of the five individual perturbation frequencies: )28204568038. vlPatent Application Docket No. T2024-161

[0107] The sensitivity (units of mm / degree) of the CoP postural response by was determined by calculating the magnitude of these FRF values at each frequency. Sensitivity is a non-negative value, and phase estimated via the frequency response functions is limited to a range between -180° and 180°. Phase values beyond ±180° were calculated using the unwrap function in Matlab.

[0108] Additionally, time domain metrics - the root mean square distance (RMSD) and the mean velocity of the ML, AP, RALP, and LARP CoP in each of the 12 conditions ((i) 1 -4, (ii)l -4, and (iii) 1 -4) was calculated. The ML, AP, RALP, and LARP RMSD were calculated by taking the root mean square distance of the zero-mean, low-pass filtered CoP signals. The ML, AP, RALP, and LARP mean velocity were determined by dividing the total distance by the duration of the trial.

[0109] Statistical Analyses. For the time domain metrics - RMSD and mean velocity -first was performed eight sets of two-way repeated measures MANOVA to evaluate the effects of Condition (i, ii, iii) and Trial (e.g., (i)-l, (i)-2, (i)-3, and (i)-4) on the eight metrics that include RMSD and mean velocity in ML, AP, RALP, and LARP directions. Bonferroni -corrected pairwise comparisons were next performed to further examine differences across all 12 trials (3 conditions x 4 trials each). Then the four trials were pooled within each condition and performed Bonferroni-corrected pairwise comparisons to evaluate condition-level differences.

[0110] For the spectral responses, Hotelling T-squared tests were used to determine whether spectral responses observed at perturbed frequencies were significantly different from zero. This helps demonstrate that those spectral responses are distinguishable from the remnant. Next four sets of fourway repeated measures MANOVA were performed using real and imaginary components for ML, AP, RALP, and LARP frequency response functions (FRF) that described the sensitivity and phase of CoP postural responses relative to the stimulus. For one-sample comparisons, Hotelling T-squared tests were29204568038. vlPatent Application Docket No. T2024-161 using the real and imaginary parts of each FRF’s complex values. When comparing two different frequency sets, the 2-dimensional difference was calculated (i.e., the difference between real and the difference between imaginary components) between the two responses at each of the 5 perturbation frequencies. To address multiple comparisons, both a commonly used Bonferroni correction to control the family-wise error rate by adjusting the significance level a from 0.05 to 0.05 divided by the number of comparisons, and the Benjamini -Hochberg (B-H) procedure to control the false discovery rate at q = 0.05, to mitigate the conservatism of the Bonferroni correction were applied.[OHl] Results

[0112] Root Mean Square Displacement (RMSD) and Mean Velocity. Repeated measures MANOVA revealed significant effects of Condition (e.g., (i), (ii), and (iii)) and Trial (e.g., (i)-l, (i)-2, (i)-3, and (i)-4) on RMSD (Condition: p < 0.001, Trial: p < 0.001) and Mean Velocity (Condition: p < 0.001, Trial: p = 0.038). A significant interaction effect of Condition and Trial on RMSD (p < 0.001) but not mean velocity (p = 0.62) was also found.

[0113] Further Bonferroni corrected pairwise comparisons found a significant difference between Condition (i) versus (iii) (p < 0.001) and Condition (ii) versus (iii) (p < 0.001) for both RMSD and Mean Velocity, which is shown in Figure 3. The asterisks delineate statistically significant differences (p < 0.05). The pairwise comparisons showed no significant differences among the four trials in Mean Velocity but indicated a significant difference between Trial 1 versus 3 in ML RMSD and Trial 1 versus 4 in LARP RMSD but not one of the other 22 trial comparisons of RMSD. The peak-to-peak amplitudes for Condition (iii) are larger than those for Condition (i) and (ii), so it was expected that Condition (iii) would evoke larger postural responses than Condition (i) or (ii) in all the directions. Peak-to-peak displacement was roughly 50% greater for Condition (iii) (range: 1.53° to 2.09°) than for Condition (i)30204568038. vlPatent Application Docket No. T2024-161 and Condition (ii) (range 0.89° to 1.40°); peak-to-peak amplitudes for Condition (i) and Condition (ii) were about the same.

[0114] Figure 3 shows box-and whisker plots of the average RMSD (A) and Mean Velocity (B) of ML, AP, RALP, and LARP CoP responses across the four trials for each condition (e.g., (i)-l, (i)-2, (i)- 3, and (i)-4). Bonferroni corrected pairwise comparisons, performed using a paired t-test, confirmed that both RMSD and Mean Velocity were significantly larger for Condition (iii) when roll, pitch, RALP, and LARP perturbations were provided simultaneously versus Condition (i) when just roll / pitch stimuli were provided and Condition (ii) when just RALP / LARP stimuli were provided in separate trials (p < 0.0001). No significant differences were observed when comparing RMSD or Mean Velocity responses evoked by roll / pitch stimuli (Condition (i)) to those evoked by RALP / LARP stimuli (Condition (ii)) (p > 0.23). With respect to Figure 3, the box-and whisker plots show the distribution of RMSD (A) and Mean Velocity (B) across the 24 subjects. Boxes show 25thto 75thpercentile. The horizontal line that splits the box shows the median and the lines that extend from the box show the range of the data. The dots that appear past the ends of whiskers represent outliers. The three colors delineate the three conditions. The asterisks delineate statistically significant differences (p < 0.05). Horizontal brackets show that across all RMSD and MVELO parameters, Condition (iii) was significantly different from Conditions (i) and (ii) (p < 0.0001), while Conditions (i) and (ii) were not significantly different from each other (p > 0.23).

[0115] Spectral Responses. Figure 4 shows the average ML, AP, RALP, and LARP CoP sway spectral response across the 24 subjects for the roll / pitch condition (i)-l (i.e., when provided SoSii for roll and S0S15 for pitch). Consistent with testing, ML CoP spectral peaks were observed at each of the five frequencies for the roll tilt stimuli (Fig. 4A); ML sway at each of the roll perturbation frequencies were the predominant response components. Similarly, AP CoP spectral peaks were observed at each of the five frequencies for the pitch tilt stimuli (Fig. 4B); AP sway at each of the pitch perturbation31204568038. vlPatent Application Docket No. T2024-161 frequencies were the predominant response components. These spectral peaks were clearly distinguishable from one another in the frequency domain. RALP and LARP CoP spectral magnitudes each show ten response components during this roll / pitch condition. This is a direct outcome of the fact that the RALP / LARP coordinates are rotated 45 degrees from the roll / pitch coordinates, so RALP spectral peaks were observed at each of the five frequencies for both roll tilt stimuli and pitch tilt stimuli (Fig. 4C); similarly, LARP spectral peaks were observed at each of the five frequencies for both roll tilt stimuli and pitch tilt stimuli (Fig. 4D).

[0116] Hotelling T-squared tests found that the spectral peaks observed at each perturbation frequency (i.e., ML for roll stimuli, AP for pitch stimuli, RALP for roll and pitch stimuli, and LARP for roll and pitch stimuli) were significantly different than zero (p < 0.0001). With respect to Figure 4, the power spectra plots show the average magnitude of the spectral response of CoP in the ML (A), AP (B), RALP (C), and LARP (D) planes across the 24 subjects when SoSn was provided for roll and S0S13 was provided for pitch (i.e., test condition (i)-l). Different asterisk colors delineate CoP sway in response to roll and pitch stimuli.

[0117] Figure 5 shows the average ML, AP, RALP, and LARP CoP sway spectral magnitude across the 24 subjects for RALP / LARP condition (ii)-l (i.e., when provided S0S13 for RALP and S0S17 for LARP). RALP spectral peaks were observed at each of the five frequencies for the RALP tilt stimuli (Fig. 5C); sway in the RALP plane at each of the RALP perturbation frequencies were the predominant response components (Fig. 5C). LARP spectral peaks were observed at each of the five frequencies for the LARP tilt stimuli (Fig. 5D); sway in the LARP plane at each of the LARP perturbation frequencies were the predominant response components (Fig. 5D). The RALP and LARP spectral peaks were distinguishable from one another. Analogous to the RALP and LARP responses shown above (Fig. 4)32204568038. vlPatent Application Docket No. T2024-161 for roll and pitch stimuli, ML (Fig. 5 A) and AP (Fig 5B) CoP spectral magnitudes each show ten response components - one for each of the RALP and LARP perturbation frequencies.

[0118] Hotelling T-squared tests found that the spectral peaks observed at each perturbation frequency (i.e., ML for RALP and LARP stimuli, AP for RALP and LARP stimuli, RALP for RALP stimuli, and LARP for LARP stimuli) were significantly different than zero (p < 0.0001).

[0119] With respect to Figure 5, the power spectra plots show the average magnitude of the spectral response of CoP in the ML (A), AP (B), RALP (C), and LARP (D) planes across the 24 subjects when S0S13 was provided for RALP and S0S17 was provided for LARP (i.e., test condition (ii)-l). Different asterisk colors delineate CoP sway in response to RALP and LARP stimuli.

[0120] Figure 6 shows the average ML, AP, RALP, and LARP CoP sway spectral magnitude across the 24 subjects for RALP / LARP condition (iii)-l (i.e., when S0S11 was provided for roll, S0S15 was provided for pitch, S0S13 was provided for RALP, and S0S17 was provided for LARP). ML spectral peaks were observed at each of the roll, RALP, and LARP perturbation frequencies (Fig. 6A); AP spectral peaks were observed at each of the pitch, RALP, and LARP perturbation frequencies (Fig. 6B). Similarly, RALP spectral peaks were observed at each of the RALP, roll, and pitch perturbation frequencies (Fig. 6C); LARP spectral peaks were observed at each of the LARP, roll, and pitch perturbation frequencies (Fig. 6D). Each CoP spectral magnitude shows 15 response components at three sets of five perturbation frequencies in the directions described above. This demonstrates that spectral postural response components were observed at each perturbation frequency - except for responses that were spatially orthogonal to the stimuli (e.g., AP responses to roll stimuli or RALP responses to LARP stimuli) - when four SoS perturbations are provided in roll, pitch, RALP, and LARP directions simultaneously.33204568038. vlPatent Application Docket No. T2024-161

[0121] Hotelling T-squared tests found that the spectral peaks observed at each perturbation frequency (i.e., ML for roll, RALP, and LARP stimuli, AP for pitch, RALP, and LARP stimuli, RALP for RALP, roll, and pitch stimuli, and LARP for LARP, roll, and pitch stimuli) were significantly different than zero (p < 0.0001).

[0122] With respect to Figure 6, the power spectra plots show the average magnitude of the spectral response of CoP in the ML (A), AP (B), RALP (C), and LARP (D) planes across the 24 subjects when SoSn was provided for roll and SoSis was provided for pitch, S0S13 was provided for RALP, and S0S17 was provided for LARP (i.e., test condition (iii)-l). Different asterisk colors delineate CoP sway in response to roll, pitch, RALP, and LARP stimuli.

[0123] Sensitivity and Phase. Figures 7 and 8 show the sensitivity (left, y-axis) and phase (right, y- axis) of the CoP spectral response relative to the perturbation stimuli in the ML, AP, RALP, and LARP planes. Consistent with earlier reports (Peterka, 2002), (1) the sensitivity increased with increasing perturbation frequency for the low to mid-frequency range (0.06-0.70 Hz) and reached a plateau for the high-frequency range (0.70-1.42 Hz), and (2) phase lag increased with increasing perturbation frequency. The sensitivity of CoP RALP and LARP in response to roll stimuli is a little lower than the sensitivity in response to pitch stimuli at the low-frequency range (0.06-0.50 Hz) but a little higher at the mid to high-frequency range (0.50-1.42 Hz) (Fig. 7C and 7D). The sensitivity of CoP ML and AP in response to RALP stimuli is slightly lower than the sensitivity in response to LARP stimuli in the low- frequency range (0.06-0.50 Hz) but slightly higher in the mid to high-frequency range (0.50-1.42 Hz) (Fig. 8A and 8B).

[0124] With respect to Figure 7, the plots show the sensitivity (left y-axis) and phase (right y-axis) of the CoP response in the ML (A), AP (B), RALP (C), and LARP (D) planes versus perturbation stimulus frequency for Test Condition (i) with S0S11 provided for roll and S0S15 provided for pitch.34204568038. vlPatent Application Docket No. T2024-161Error bars show 95% confidence intervals. Different asterisk colors delineate the average sensitivity of CoP sway in response to roll and pitch stimuli.

[0125] With respect to Figure 8, the plots show the sensitivity (left y-axis) and phase (right y-axis) of the CoP response in the ML (A), AP (B), RALP (C), and LARP (D) planes versus perturbation stimuli frequency for Test Condition (ii) with S0S13 provided for RALP and S0S17 provided for LARP. Error bars show 95% confidence intervals. Different asterisk colors delineate the average sensitivity of CoP sway in response to RALP and LARP stimuli.

[0126] The real and imaginary components of ML, AP, RALP, and LARP spectral responses were evaluated using a four-way repeated measures MANOVA to find a difference when the stimuli were provided in roll / pitch coordinates versus RALP / LARP coordinates. The four factors were (1) the three stimulus directions that were not orthogonal to the response direction (e.g., roll, RALP, and LARP tilts, but not pitch tilt, for the ML response), (2) the four sets of perturbation frequencies (i.e., S0S11, S0S13, S0S15, and S0S17), (3) the five frequencies for each set (i.e., fi, fz, f3, fi, and fs), and (4) the three test conditions (i.e., roll / pitch only, RALP / LARP only, and simultaneous roll / pitch + RALP / LARP conditions). Mauchly's test indicated the sphericity assumption was invalid. While some statistically significant differences were observed, a clear pattern of differences was not evident. That some differences were statistically significant, alongside violation of the sphericity assumption, encouraged additional statistical evaluation of these data using more refined analyses, Hotelling’s T-squared analyses with Bonferroni correction and the Benjamini -Hochberg (BH) procedure, which follow.

[0127] Roll / Pitch stimuli and RALP / LARP stimuli evoke similar AP, ML, RALP, and LARP responses.

[0128] 1. Simultaneous roll / pitch / RALP / LARP stimuli (160 comparisons). The top panels of Figure9 show the average frequency response functions in the complex plane across the 24 healthy subjects35204568038. vlPatent Application Docket No. T2024-161 when the simultaneous roll / pitch / RALP / LARP stimuli (i.e., Condition (iii)) were provided. The radius of the complex number ( r = a2+ b2for the complex number is a + bi ) represents the sensitivity (mm / deg) of the postural response relative to the stimulus. The angle of the complex number represents the phase (0 = atan2 b, a)), where atan2 is the 4-quadrant arc tangent) of the postural response relative to the stimulus. The frequency response functions spiral clockwise with increasing perturbation frequency. These plots show the real and imaginary components of the responses, which will be used for the Hotelling’s T-squared analyses that follow. Specifically, a Hotelling’s T-squared test was performed to compare: (a) ML sway evoked by roll stimuli versus RALP stimuli; (b) ML sway evoked by roll stimuli versus LARP stimuli; (c) AP sway evoked by pitch stimuli versus RALP stimuli; (d) AP sway evoked by pitch stimuli versus LARP stimuli; (e) RALP sway evoked by RALP stimuli versus roll stimuli; (f) RALP sway evoked by RALP stimuli versus pitch stimuli; (g) LARP sway evoked by LARP stimuli versus roll stimuli; and (h) LARP sway evoked by LARP stimuli versus pitch stimuli.

[0129] After calculating the discrete Fourier transform, the vector difference was taken between the real and imaginary components of the two spectra (e.g., normalized ML sway in response to roll stimuli minus normalized ML sway in response to RALP stimuli) at each stimulation frequency for each participant. The above 8 conditions (a through h) x 4 SoS signals x 5 frequencies yielded 160 Hotelling’s T-squared comparisons in total. Without correcting for multiple comparisons, 26 significant differences were found (p < 0.05). Bonferroni correction and the Benjamini -Hochberg (BH) procedure found no significant difference between any of these 160 postural response components. To provide context for later results, Table 3 shows the ten lowest uncorrected p-values and the associated BH critical values.

[0130] Stated differently, when roll / pitch / RALP / LARP stimuli were provided simultaneously, it was found: (1) that ML postural responses to roll stimuli were not significantly different from ML responses36204568038. vlPatent Application Docket No. T2024-161 to RALP or LARP stimuli, (2) that AP postural responses to pitch stimuli were not significantly different from AP responses to RALP or LARP stimuli, (3) that RALP postural responses to RALP stimuli were not significantly different from RALP responses to roll or pitch stimuli, and (4) that LARP postural responses to LARP stimuli were not significantly different from LARP responses to roll or pitch stimuli.

[0131] With respect to Figure 9, the average frequency response functions of CoP (A) ML, (B) AP, (C) RALP, and (D) LARP in the complex plane across the 24 subjects (top) when simultaneous roll / pitch / RALP / LARP stimuli were provided using SoSn (i.e., Condition (iii)) and (bottom) when roll / pitch stimuli (i.e., Condition (i)) were provided using SoSn on separate trials than RALP / LARP stimuli (i.e., Condition (ii)). Different asterisk colors delineate the average frequency responses to roll, pitch, RALP, and LARP stimuli. All plots spiraled clockwise with increasing frequency.

[0132] Table 3 illustrates the ten lowest p-values of 160 comparisons (a) through (h) during simultaneous roll / pitch / RALP / LARP stimuli (i.e., Condition (iii)) are listed. By definition, the familiar, though conservative, Bonferroni correction equals the first BH value, which is 0.0003 for this analysis. For context, response direction analyzed, stimuli compared, frequency, and SoS test set are also listed.Table 3 p-vahse BH Response Stimuli Frequency Set204568038. vlPatent Application Docket No. T2024-161

[0133] 2 Roll / Pitch stimuli and RALP / LARP stimuli provided on separate trials (160 comparisons).The bottom panels of Figure 9 show the average frequency response functions in the complex plane across the 24 healthy subjects when the 2D roll / pitch stimuli (i.e., Condition (i)) were provided on separate trials than the 2D RALP / LARP stimuli (i.e., Condition (ii)). The frequency response functions again spiral clockwise with increasing perturbation frequency. Our Hotelling’s T-squared analyses of these data mimicked the analyses presented in the previous section where the roll, pitch, RALP, and LARP stimuli were all presented simultaneously. Hotelling’s T-squared testing yielded 31 significant differences (p < 0.05) out of 160 comparisons. A Bonferroni correction and the BH procedure each yield one (by definition, the same) significant difference - the LARP response to roll stimuli yielded a significantly different LARP response than evoked by the LARP stimuli at 1.4465 Hz (fs) for the S0S15 (p < 0.00031). It is noted that not one of the other three frequency sets (S0S11, S0S13, and S0S17) showed a significant difference for this same condition following the BH procedure. To provide context for later results, Table 4 shows the ten lowest uncorrected p-values and the associated BH critical values. The five lowest p-values were all found at fs, the highest frequency

[0134] With respect to Tabel 4, the ten lowest p-values of 160 comparisons (a) through (h) when the roll / pitch stimuli (i.e., Condition(i)) and the RALP / LARP stimuli (i.e., Condition(ii)) were provided on separate trials. By definition, the familiar, though conservative, Bonferroni correction equals the first BH value, which is 0.0003 for this analysis. For context, response direction analyzed, stimuli compared, frequency, and SoS test set are also listed.Table 438204568038. vlPatent Application Docket No. T2024-161 p-value BH Response Stimuli Frequency Set

[0135] In summary, these results (i.e., when the 2D roll / pitch stimuli were provided on different trials than the 2D RALP / LARP stimuli) appear similar to results when roll / pitch / RALP / LARP stimuli were provided simultaneously. Specifically, it was found that ML, AP, RALP, and LARP postural responses were not significantly different when the 2D stimuli were provided in roll / pitch coordinates versus RALP / LARP coordinates.

[0136] Small frequency shifts associated with the different SoS frequency sets yield significant differences in postural responses. Earlier publications, as well as our data (Figures 7 and 8), clearly establish that responses to balance perturbations vary systematically with frequency. Nevertheless, to help establish the sensitivity of these methods to small frequency changes and to tell if responses can be directly compared at nearby individual frequencies across our four different stimuli sets (SoSn, S0S13, S0S15, S0S17), the impacts of small frequency changes were evaluated on the postural responses utilizing the four SoS signals described in detail in the methods (Fig. 2). Using formatting similar to Figure 9, Figure 10 shows the average frequency response functions of ML, AP, RALP and LARP CoP sway in the complex plane at the five perturbation frequencies for S0S11, S0S13, S0S15, and S0S17 when provided as: (i) roll / pitch only, (ii) RALP / LARP only, and (iii) roll / pitch / RALP / LARP. The data demonstrates distinct separations for the different sets of the five perturbation frequencies.204568038. vlPatent Application Docket No. T2024-161

[0137] Analogous to earlier analyses, 240 comparisons were performed using Hotelling’s T-squared test to investigate how those four specific frequency sets (SoSn, SoS 13, SoS 15, and SoS 17) and their five frequencies (fi through fs) affect ML, AP, RALP, and LARP CoP sway. After calculating the discrete Fourier transform, the vector difference was taken between the real and imaginary components of the two spectra for each stimulation frequency for each participant and performed a Hotelling’s T-square test to compare CoP in response to (aa) S0S11 and S0S13, (bb) S0S11 and S0S15, (cc) S0S11 and S0S17, (dd) S0S13 and S0S15, (ee) S0S13 and S0S17, and (ff) S0S15 and S0S17. This yielded 60 comparisons (each of 6 SoS stimuli comparisons x each of 5 frequencies x each of 2 response directions) for (i) roll / pitch only, 60 comparisons for (ii) RALP / LARP only, and 120 comparisons for (iii) roll / pitch / RALP / LARP (each of 6 SoS stimuli comparisons x each of 5 frequencies x each of 4 response directions), which means 240 comparisons in total. Hotelling’s T-squared test found 168 significant differences. Bonferroni correction yielded 75 significant differences, which is 31.25 % of the p-values, and the B-H procedure yielded 145 significant differences, which is 60.41 % of the p-values. Table 5 shows the ten lowest original p-values and the individual p-values’ BH critical values. Specifically, it was found that small frequency shifts between (aa) S0S11 and S0S13, (bb) S0S11 and S0S15, (cc) S0S11 and S0S17, (dd) S0S13 and S0S15, (ee) S0S13 and S0S17, and (ff) S0S15 and S0S17 yielded significant differences in postural responses.

[0138] Stated briefly, when comparing responses at distinct frequencies from our four perturbation trajectories that were separated by 0.01 10-0.1208 Hz (i.e., small differences in perturbation frequencies), statistically significant differences were found for the majority of these comparisons. Since it was known that postural responses vary with frequency, the finding that the majority of comparisons yielded significant differences helps establish the sensitivity of these Hotelling’s T-squared methods to detect40204568038. vlPatent Application Docket No. T2024-161 even subtle differences associated with small changes in perturbation frequency, which bolsters the absence of significant differences reported above.

[0139] With respect to Figure 10, the average frequency response functions of CoP (A) ML, (B) AP, (C) RALP, and (D) LARP in the complex plane across the 24 subjects (top) when simultaneous roll / pitch / RALP / LARP stimuli were provided (i.e., Condition (iii)) and (bottom) when roll / pitch stimuli (i.e., Condition (i)) were provided on separate trials than RALP / LARP stimuli (i.e., Condition (ii)). Different asterisk colors delineate the average frequency responses to SoSn, SOSB, S0S15, and S0S17 stimuli. All plots spiraled clockwise with increasing frequency.

[0140] Table 5 shows the ten lowest p-values of 240 comparisons between different frequency sets (aa)-(ff).Table 5

[0141] In this study, 24 healthy participants were recruited to measure changes in the CoP evoked by pseudorandom SoS platform perturbations to characterize reactive balance in three conditions. In Condition (i), two distinct balance perturbation stimuli were provided that were orthogonal in both time and space in the roll and pitch tilt motion dimensions. In Condition (ii), two distinct balance perturbation stimuli that were orthogonal in both time and space were provided in the RALP and LARP tilt motion41204568038. vlPatent Application Docket No. T2024-161 dimensions defined by the anatomy of the semicircular canals (Figure 1). In Condition (iii), four distinct balance perturbation stimuli that were orthogonal in time (but not space) in the roll, pitch, RALP, and LARP tilt motion dimensions were provided. We were able to quantify AP and ML responses even when the perturbation stimuli were provided in RALP / LARP coordinates (i.e., Condition (ii)). The AP and ML responses were not significantly different from those evoked by the perturbation stimuli provided in roll / pitch coordinates. These primary findings demonstrate the potential of the platform perturbations provided in RALP / LARP coordinates as a new balance assessment that will ultimately help observe the balance impairment of individuals with asymmetric sensory deficits in the vertical semicircular canals.

[0142] Spectral response components. Consistent with the experimental procedures performed and discussed here, (a) tilt perturbations in the roll plane yielded responses primarily in the ML direction (Figure 5A) with only small responses in the AP direction (Figure 5A), and (b) tilt perturbations in the pitch plane yielded responses primarily in the AP direction (Figure 5B) with only small responses in the ML direction (Figure 5B). As findings, it can be reported that (c) tilt perturbations in the RALP plane yielded responses primarily in the RALP direction (Figure 6C) with only small responses in the LARP direction (Figure 6C), and (d) tilt perturbations in the LARP plane yielded responses primarily in the LARP direction (Figure 6D) with only small responses in the RALP direction (Figure 6D).

[0143] In Condition (i), where simultaneous roll and pitch stimuli were provided, it was found that the largest response components were in the ML and AP directions (Figure 5A, 5B). When one looks at these same data in coordinates that align with the RALP and LARP directions, it (by the relationship between these two different reference frames) is found that response components that reflect the projection of the roll and pitch responses onto the RALP and LARP directions (Figure 5C, 5D).42204568038. vlPatent Application Docket No. T2024-161

[0144] In Condition (ii), where simultaneous RALP and LARP stimuli were provided, it was found that the largest response components were in the RALP and LARP directions (Figure 6C, 6D). Again, because of the mathematical nature of reference frames that are rotated with respect to one another, when these same data in ML and AP coordinates are viewed, response components are found that reflect the projection of the predominant RALP and LARP responses onto the ML and AP directions (Figure 6 A, 6B).

[0145] In Condition (iii), where simultaneous stimuli in each of 4 planes were provided (i.e., roll, pitch, RALP, and LARP) - each having 5 different stimulus frequencies, frequency response components were found at all 20 frequencies. Clear response components were found for: (a) roll, RALP, and LARP for each frequency of the roll stimuli, (b) pitch, RALP, and LARP for each frequency of the pitch stimuli, (c) roll, pitch, and RALP for each frequency of the RALP stimuli, and (d), roll, pitch, and LARP for each frequency of the LARP stimuli. In other words, clear response components were found at each stimulation frequency except that clear consistent response components were not found in the response direction that was spatially orthogonal to the stimulus direction.

[0146] No significant differences in ML and AP responses between roll / pitch stimuli and RALP / LARP stimuli. The repeated measures MANOVA using real and imaginary components found that the ML and AP responses were not significantly different when the tilt stimuli were provided in roll / pitch coordinates versus RALP / LARP coordinates (Pillai’s Trace, AP: p = 0.48, ML: p = 0.63)). Similarly, Hotelling’s T-square for further pairwise comparisons found no significant differences in the sensitivity of ML and AP spectral responses between roll and pitch tilt stimuli versus RALP and LARP tilt stimuli after the Bonferroni correction and the Benjamini -Hochberg (BH) procedure. This was true when the roll and pitch stimuli were provided in different trials (i.e., Condition (i)) than the RALP and LARP stimuli (i.e., Condition (ii)) and when the roll, pitch, RALP, and LARP stimuli were provided43204568038. vlPatent Application Docket No. T2024-161 simultaneously in the same trial (i.e., Condition (iii)). This suggests that comparison can be made between ML and AP responses evoked by RALP and LARP stimuli to existing literature showing ML and AP responses evoked by roll and pitch stimuli.

[0147] Putting all of the above into context, this suggests that tilt stimuli in the RALP and LARP coordinates can be provided and: (1) Quantify the ML and AP responses evoked by RALP and LARP tilt stimuli, making it straightforward to compare with - and build on - the pre-existing literature that typically quantifies ML and AP responses evoked by ID roll or ID pitch stimuli; and (2) Quantify the responses in those RALP / LARP coordinates, making it easier to separate contributions of the RALP semicircular canals from the LARP canals.

[0148] For example is a patient has a lesion in the right anterior semicircular canals, the patient will show a larger postural response to RALP tilt stimuli than to LARP tilt stimuli due to the limited contribution of the right anterior semicircular canals. 2D balance perturbations in roll / pitch coordinates are less likely to distinguish balance impairment due to sensory deficits in the vertical semicircular canals (i.e., RALP and LARP) as all of the four vertical semicircular canals contribute to postural control at the same time when perturbations are provided in roll or pitch coordinates.

[0149] In some aspects, translation stimuli in the AP and ML directions can be providing while tilt stimuli in the RALP and LARP directions can be simultaneously provided. Consistent with the approach shown herein, these four stimuli will all be orthogonal in time and spectrally separable. Nonetheless, providing the tilt stimuli in RALP / LARP directions and translation in the more traditional ML and AP directions adds spatial separation alongside the orthogonality in time and spectral separation

[0150] Frequency response functions. The plots of the sensitivity and phase of the CoP spectral responses (Figures 7 and 8) are also qualitatively similar to earlier studies that provided pseudorandom pitch tilt stimuli with eyes closed and roll tilt stimuli with eyes closed. Prior research generated support44204568038. vlPatent Application Docket No. T2024-161 surface pitch tilts using a pseudorandom ternary sequence (PRTS) and quantified Center of Mass (CoM) AP body sway angles of 8 healthy subjects using a backboard. It was found (1) that transfer function gain increased in the low-mid frequency range (0.0165-0.5 Hz) and decreased in the higher frequency range (0.5-2.48 Hz) and (2) that phase lag continuously increased with frequency. Another prior study estimated CoM ML body sway angles using a backboard and demonstrated that transfer function gain increased with frequency below 0.5 Hz and phase lag continuously increased with frequency in a bandwidth of 0.021-2.79 Hz in response to roll support surface PRTS tilts. These two earlier studies generally align with the FRF characteristics found in the present study that used a bandwidth of 0.06- 1.41 Hz.

[0151] CoP FRFs did not show a decrease in sensitivity above 0.50 Hz. Prior work suggested that CoM body sway angles can be estimated by lowpass-filtering CoP data with a cut-off frequency of 0.47 Hz. The present study measured changes in CoP displacement and filtered the CoP data with a cut-off frequency of 20Hz to avoid losing information about the postural response above 0.47Hz. This difference in filtering data leads to different gain characteristics above 0.50 Hz.

[0152] As will be appreciated, in some aspects, small changes in frequency can matter. Four pseudorandom SoS trajectories were created that were designed to have frequency components that were close to each other (Table 1). Even though frequency response functions varied with frequency, in accordance with aspects herein, it is hypothesized that the small frequency differences designed would not yield significant response differences because the frequencies were near to one another (e.g., SoSn fi = 0.0604 Hz and S0S17 fi = 0.0934 Hz) and because the response variability between participants would be too large to yield significant differences. However, the four-way repeated measures MANOVA showed a significant effect of the four pseudorandom SoS trajectories (i.e., S0S11, S0S13, S0S15, and S0S17) on the responses (p < 0.001). The Hotelling’s T-square for further pairwise45204568038. vlPatent Application Docket No. T2024-161 comparisons also indicated that those four trajectories evoked significantly different responses (Table 5). This suggests that comparison should not be made between frequency response functions (FRFs) at different perturbation frequencies (e.g., fi of S0S11 versus fi of S0S13) as small changes in frequency matter for these FRFs. This is an unexpected finding because this shows the power of the approach presented herein, where statistically significant differences in the postural response were found for nearby stimulation frequencies; this shows that response variability had to have been small enough to unveil the response differences evoked by small differences in the stimulus frequency. This would not have occurred if the methods didn’t yield clean spectral response components.

[0153] Technical considerations. Positive integers only were used to multiply the fundamental frequency to determine the frequency of all stimulus components. This means that complete cycles for each frequency are provided in each full period of stimulation. This makes the stimuli provided at each frequency orthogonal in time over the full steady-state period. Both theoretically and practically, this means that no stimulus frequency components interfere with any other stimulus frequency components. Theoretically, the same holds true for steady-state responses of any linear system, as is commonly assumed by many studies of the balance responses evoked by ID balance perturbations.

[0154] A smaller fundamental frequency (0.0055Hz) was chosen than the one selected (0.044Hz) in previous experiments to allow all perturbation frequencies to fit in our target bandwidth of 0.05-2.00 Hz. This bandwidth was selected because early literature showed that vestibular thresholds decreased with increasing frequency in the bandwidth (Lim et al., 2017). To define our frequency components, the fundamental frequency of 0.0055Hz was multiplied by prime numbers with the single exception of 15;15 was included, since its prime factors of 3 and 5 were not included as multipliers. This set of multipliers - like sets of prime number multipliers - reduces the chance of system nonlinearities yielding overlapping response frequency components.46204568038. vlPatent Application Docket No. T2024-161

[0155] It was chosen to begin with 1 1 as the lowest multiplier. This meant that a minimum of 11 cycles of stimuli were provided for each complete fundamental period of stimulation. This is above the minimum rule of 5 to 7 cycles often required for spectral analyses.

[0156] Choosing 11 as the lowest multiplier also allowed to also include 13, 15, and 17 as the lowest integer multipliers, which leads to the fundamental frequency of the four trajectories used herein being separated only by a factor of 1.55. In other words, there was an increase of 55% from the lowest fundamental frequency of 0.060 Hz to the highest fundamental frequency of 0.093 Hz -meaning that these 4 stimuli all had similar - but separable — fundamental frequencies. See Figure 2 and Table 1.

[0157] To accomplish an analogous goal, two pseudorandom ternary sequence (PRTS) stimuli with non-overlapping harmonics have been interleaved by doubling the fundamental frequency of the 2ndstimuli (e g., a 100% increase). Taking this approach for four stimuli - like those provided in our Condition (iii) would result in the fourth fundamental frequency (i.e., S0S17 fi) being 8 times greater than the first fundamental frequency (i.e., S0S11 fi) (i.e., a 700% increase). For 12 stimuli (e.g., 6 physical motion dimensions and 6 visual motion dimensions), this approach of doubling the fundamental frequency for each motion dimension stimulated would mean that the highest fundamental frequency would be 2048 times greater (i.e., 2(12-1), which is more than 3 orders of magnitude greater) than the lowest fundamental frequency - almost certainly putting either the lowest or the highest fundamental frequency outside the physiologic range of interest.

[0158] It was chosen to perform our statistics using the real and imaginary Cartesian-coordinate response components instead of the more traditional polar coordinate response components of magnitude and phase. Standard coordinate transformations were used to convert back-and-forth from the standard Cartesian coordinates (i.e., real and imaginary components) and standard polar coordinates (i.e., magnitude and phase). The Cartesian coordinates offer the advantage that these two independent47204568038. vlPatent Application Docket No. T2024-161 variables are each unbounded (i.e., range from minus co to plus co). For comparison, magnitude is bounded at zero (i.e., is non-negative) and phase of the Fourier transform is bounded to fall in a range of -180 to 180°. As is discovered, these bounds alter statistical calculations even though the data points being compared are identical. While phase “unwrapping” can yield a greater phase range as the function shifts the angles to make the jump between consecutive angles less than 180° the unwrapping process is always subject to assumptions, which are avoided by simply using the real and imaginary components. Furthermore, the units on the real and imaginary variables are always the same, which means the weighting in all calculations - including, but not limited to, statistical calculations - is also naturally the same.

[0159] The present examples demonstrate (1) that spectral response components were observed at each perturbed frequency when provided with two distinct balance perturbation stimuli in roll / pitch coordinates or / and RALP / LARP coordinates, (2) that the AP and ML postural responses were not significantly different when the stimuli were provided in roll / pitch coordinates versus RALP / LARP coordinates except for one of 320 comparisons as described in the results, (3) that even small shifts in perturbation frequency impact quantification of spectral postural responses, and (4) that spectral response components were observed at each of the 20 perturbation frequencies when SoS perturbations were provided in the four directions (roll, pitch, RALP, and LARP) simultaneously. These findings highlight that healthy individuals show similar postural sway in response to roll / pitch stimuli that are orthogonal to one another in both space and time, and RALP / LARP stimuli that are similarly orthogonal to one another in both space and time.ADDITIONAL EMBODIMENTS

[0160] Some additional, non-limiting, example embodiments are provided below.48204568038. vlPatent Application Docket No. T2024-161

[0161] Embodiment 1 . A system for balance and / or gait perturbation and measurement, the system comprising: a balance measurement device, and an actuator driven motion platform, the motion platform configured to independently tilt and / or move in at least two directions based on at least two balance perturbation stimuli.

[0162] Embodiment 2. A system for testing and training vestibular and balance function, comprising the system of embodiment 1.

[0163] Embodiment 3. A system for testing and training vestibular and balance function, comprising: a six degree of freedom (6DoF) motion platform, the motion platform comprising: a moving platform, and six linear actuators attached to the moving platform configured as movement axes to drive the moving platform, wherein the moving platform is configured to move independently in one or more directions based on delivered perturbation stimuli.

[0164] Embodiment 4. The system of embodiment 3, wherein each actuator comprises a ball joint at its distal end.

[0165] Embodiment 5. The system of embodiment 3, wherein the motion platform is configured to provide 3 DoF movement of translation along the movement axes.

[0166] Embodiment 6. The system of embodiment 3, wherein the motion platform is configured to provide 3 DoF movement of rotation and / or tilt about the movement axes.

[0167] Embodiment 7. The system of embodiment 3, wherein at least two perturbation stimuli are delivered to the motion platform.

[0168] Embodiment 8. The system of embodiment 3, wherein at least two balance perturbation stimuli are delivered to the motion platform simultaneously.

[0169] Embodiment 9. The system of embodiment 3, wherein the perturbation stimuli are spectrally separated sums of sinusoids (SoS) perturbation trajectories.49204568038. vlPatent Application Docket No. T2024-161

[0170] Embodiment 10. The system of embodiment 3, wherein the moving platform has a predetermined displacement limit of translation.

[0171] Embodiment 11. The system of embodiment 3, wherein the moving platform has a predetermined displacement limit of tilt and / or rotation.

[0172] Embodiment 12. The system of embodiment 3, further comprising one or more of a chair, an adjustable helmet, a forceplate, and a safety barrier.

[0173] Embodiment 13. The system of embodiment 3, wherein the platform can be configured for either balance testing or vestibular testing.

[0174] Embodiment 14. The system of embodiment 12, further comprising rails to slide and / or move the chair into a vestibular test configuration or into a balance test configuration.

[0175] Embodiment 15. A method for testing and training vestibular and balance functions, the method comprising: determining at least two balance perturbation stimuli, perturbing the balance of a subject independently in at least two directions, based on the at least two balance perturbation stimuli, and measuring at least one aspect of balance of the subject.

[0176] Embodiment 16. The method of embodiment 15, wherein two distinct balance perturbation stimuli are provided that are orthogonal in both time and space in the roll and pitch tilt motion dimensions

[0177] Embodiment 17. The method of embodiment 15, wherein two distinct balance perturbation stimuli that were orthogonal in both time and space were provided in the RALP and LARP tilt motion dimensions.

[0178] Embodiment 18. The method of embodiment 15, wherein four distinct balance perturbation stimuli are provided that are orthogonal in time in the roll, pitch, RALP, and LARP tilt motion dimensions.50204568038. vlPatent Application Docket No. T2024-161

[0179] Embodiment 19. The method of embodiment 15, wherein the determining comprises generating at least two sum of sines (SoS) balance perturbation trajectories.

[0180] Embodiment 20. The method of embodiment 19, wherein the at least two sum of sines (SoS) balance perturbation trajectories are orthogonal to each other in the time domain and / or separable in the frequency domain

[0181] Embodiment 21. The method of embodiment 19, wherein determining the at least two frequency components comprises determining a fundamental frequency, and selecting a plurality of interleaved integers that multiply the fundamental frequency.

[0182] Embodiment 22. The method of embodiment 15, wherein each sum of sines (SoS) balance perturbation trajectory is assigned to a direction of perturbation

[0183] Many different arrangements of the various components and / or steps depicted and described, as well as those not shown, are possible without departing from the scope of the claims below.Embodiments of the present technology have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent from reference to this disclosure. Alternative means of implementing the aforementioned can be completed without departing from the scope of the claims below. Certain features and subcombinations are of utility and can be employed without reference to other features and subcombinations and are contemplated within the scope of the claims.51204568038. vl

Claims

Patent Application Docket No. T2024-161CLAIMS1. A system for testing and training vestibular and balance function, comprising: a six degree of freedom (6D0F) motion platform, the motion platform comprising: a moving platform; and six linear actuators attached to the moving platform configured as movement axes to drive the moving platform, wherein the moving platform is configured to move independently in one or more directions based on delivered perturbation stimuli.

2. The system of claim 1, wherein each actuator comprises a ball joint at its distal end.

3. The system of claim 1, wherein the motion platform is configured to provide 3 DoF movement of translation along the movement axes.

4. The system of claim 1, wherein the motion platform is configured to provide 3 DoF movement of rotation and / or tilt about the movement axes.

5. The system of claim 1, wherein at least two perturbation stimuli are delivered to the motion platform.

6. The system of claim 1, wherein at least two balance perturbation stimuli are delivered to he motion platform simultaneously.52Patent Application Docket No. T2024-1617. The system of claim 1, wherein the perturbation stimuli are spectrally separated sums of sinusoids (SoS) perturbation trajectories.

8. The system of claim 1, wherein the moving platform has a predetermined displacement limit of translation.

9. The system of claim 1, wherein the moving platform has a predetermined displacement limit of tilt and / or rotation.

10. The system of claim 1, further comprising one or more of a chair, an adjustable helmet, a forceplate, and a safety barrier.

11. The system of claim 1, wherein the platform can be configured for either balance testing or vestibular testing.

12. The system of claim 10, further comprising rails to slide and / or move the chair into a vestibular test configuration or into a balance test configuration.

13. A method for testing and training vestibular and balance functions, the method comprising: determining at least two balance perturbation stimuli; perturbing the balance of a subject independently in at least two directions, based on the at least two balance perturbation stimuli; and53Patent Application Docket No. T2024-161 measuring at least one aspect of balance of the subject.

14. The method of claim 13, wherein two distinct balance perturbation stimuli are provided that are orthogonal in both time and space in the roll and pitch tilt motion dimensions.

15. The method of claim 13, wherein two distinct balance perturbation stimuli that were orthogonal in both time and space were provided in the RALP and LARP tilt motion dimensions.

16. The method of claim 13, wherein four distinct balance perturbation stimuli are provided that are orthogonal in time in the roll, pitch, RALP, and LARP tilt motion dimensions.

17. The method of claim 13, wherein the determining comprises generating at least two sum of sines (SoS) balance perturbation trajectories.

18. The method of claim 17, wherein the at least two sum of sines (SoS) balance perturbation trajectories are orthogonal to each other in the time domain and / or separable in the frequency domain.

19. The method of claim 17, wherein determining the at least two frequency components comprises: determining a fundamental frequency, and selecting a plurality of interleaved integers that multiply the fundamental frequency.54Patent Application Docket No. T2024-16120. The method of claim 13, wherein each sum of sines (SoS) balance perturbation trajectory is assigned to a direction of perturbation.55

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