High-density brain electrode assembly for reading and / or stimulating brain tissue

Abstract

The present invention relates to a high-density brain electrode assembly, the high-density brain electrode assembly comprising: an elongated main shaft having a plurality of guide lumens, the guide lumens extending to a distal end of the main shaft; a plurality of elongated electrode shanks, each electrode shank having a plurality of electrical contacts, passing through one of the plurality of guide lumens, and being movable from a retracted position where each electrode shank is retracted within the main shaft to an extended position where the electrode shank extends distally beyond the distal end of the main shaft; a plurality of shuttle elements, each shuttle element passing through one of the plurality of guide lumens and being movable from a retracted position where the shuttle element is retracted at the distal end of the main shaft to an extended position where the shuttle element extends distally beyond the distal end of the main shaft; wherein the electrode shanks are more flexible than the shuttle elements, each shuttle element is connected to one of the plurality of electrode shanks to move the respective electrode shank from the retracted position to the extended position; and the high-density brain electrode assembly is configured to distribute distal ends of the electrode shanks over a surface area larger than a maximum cross-sectional area of the distal end of the main shaft in a plane perpendicular to the longitudinal axis of the main shaft.

Description

Technical Field

[0001] The present disclosure relates to the field of biomedical engineering, and more particularly to high-density brain electrode assemblies, such as high-density brain reading and / or stimulation electrode assemblies for reading and / or stimulating the lateral geniculate nucleus of the thalamus to create vision in mammals. The present invention also relates to a neuroprosthetic system and method for replacing or guiding a defective or impaired sensory function in a mammal by electrical stimulation of the electrodes of such a high-density brain electrode assembly, for example, restoring functional vision in a human suffering from partial or complete blindness.

Background Art

[0002] Neuroprosthetics or neuroprosthesis is a technical field related to neuroscience and biomedical engineering regarding the development of neuroprosthetics. A sensory prosthesis, in its most common form, is a device or system designed to replace or guide sensory functionality such as visual functionality, auditory functionality, tactile functionality, or olfactory functionality that may have been damaged as a result of injury or disease by nerve reading and / or stimulation in respective regions of the mammalian cerebral cortex.

[0003] In the field of sensory restoration of visual function, for example, visual system injuries can be broadly classified into a first group having injuries to the visual processing pathway up to the ganglion cell layer of the retina and a second group having injuries that disrupt the flow of information between the retina and the visual cortex after processing.

[0004] For patients in the first group, there have been significant advances in the form of gene therapy in the retina and artificial retinas for transplantation into the retina that cause low vision in mammals, and the retinal ganglion cells that connect the eye to the brain are left intact. Retinal implants and gene therapy cannot be used for people with extensive damage to the ganglion cells and / or the optic nerve. For the large population of patients who cannot recover vision in the retina, i.e., the second group described above, prostheses composed of surface electrical contacts for application over the outer surface of the visual cortex, and prostheses containing electrodes for activation of neurons located deeper in the visual cortex have been developed, enabling the generation of a sparse subset of phosphenes.

[0005] WO20043790A1 discloses a neural prosthesis system for replacing mammalian sensory modalities by electrical stimulation of regions of the mammalian cerebral cortex corresponding to the neural modalities to be replaced, the system being characterized by comprising: at least one sensor configured to generate a sensed data feed by detecting the neural modality to be replaced, for use by a mammal; an electrode unit comprising a plurality of three-dimensional arrays of flexible elongated electrode shafts arranged for intracortical implantation to densely occupy such regions of the mammalian cerebral cortex and arranged to provide functional coverage of the sensory modality, each shaft comprising a plurality of electrical contacts for electrical stimulation of a subset of positions in the above-mentioned region of the cerebral cortex; a rigid electrode support structure configured to simultaneously guide the above-mentioned flexible electrode shafts of the array into the above-mentioned region of the mammalian cerebral cortex during intracortical implantation and to retract the support structure after implantation of the array of flexible electrode shafts; a drive unit configured to electrically drive the electrode unit to stimulate a subset of positions in the above-mentioned region of the cerebral cortex; a recording unit configured to obtain neural recordings through the electrode unit in the above-mentioned region of the cerebral cortex; and a processing unit configured to analyze the sensed data feed to provide a stimulation pattern for electrically driving a group of electrical contacts of the electrode unit corresponding to a subset of positions in the above-mentioned region of the cerebral cortex and configured to replace the above-mentioned sensory modality.

[0006] The neural prosthetic system of WO20043790A1, the content of which is incorporated herein by reference in its entirety, is based on the insight that functional replacement of impaired nerve modalities requires electrical stimulation of high-density sites in each region of the cerebral cortex that provides functional coverage of sensory modalities. This is achieved by providing a plurality of three-dimensional arrays of flexible electrode shanks and a rigid electrode support structure, and inserting all of the flexible electrode shanks of the arrays into the target region of the mammalian cerebral cortex simultaneously (i.e., in one step that displaces all of the electrode shanks of one array together rather than one by one), and arranging it so that the support structure is retracted after transplantation of the flexible electrode shanks.

[0007] In this way, a dense set of very thin flexible electrode shanks for uniform stimulation of positions in the cortex can be applied, especially to cortical regions such as the sulci of the cerebral cortex or regions of the cortex that are difficult to access. As a result, these regions have electrodes densely distributed in the corresponding region of the cerebral cortex of the patient or mammal, and functional coverage of sensory modalities is achieved.

[0008] To improve or restore the functional vision of a mammal suffering from partial or complete blindness, another location suitable for providing electrical stimulation to create visual perception in the mammal is the Lateral Geniculate Nucleus (LGN) of the thalamus. Also, other non-superficial locations within the brain of a mammal, such as deeper structures of the cortex, may be suitable for applying electrical stimulation or for performing electrical readout of brain tissue. Summary of the Invention Problems to be Solved by the Invention

[0009] The electrode unit disclosed in WO20043790A1 is not arranged to stimulate the LGN, which is located deeper in the brain and has a smaller volume than the visual cortex. Furthermore, implantation of this electrode unit into the brain requires a major surgical impact involving temporary removal of most of the patient's skull.

[0010] There is a need for an electrode assembly for reading and / or stimulating the brain that can be used for electrical reading and / or stimulation of non - superficial brain tissue and can be implanted with less surgical impact on the patient.

Means for Solving the Problem

[0011] The present invention provides a high - density brain electrode assembly for reading and / or stimulating brain tissue, the high - density brain electrode assembly comprising: an elongated main shaft having a plurality of guide lumens, the guide lumens extending to the distal end of the main shaft; a plurality of elongated electrode shanks, each electrode shank having a plurality of electrical contacts, each electrode shank passing through one of the plurality of guide lumens and being movable from a retracted position in which the electrode shank is retracted within the main shaft to an extended position in which the electrode shank extends distally beyond the distal end of the main shaft; a plurality of shuttle elements, each shuttle element passing through one of the plurality of guide lumens and being movable from a retracted position in which the shuttle element is retracted at the distal end of the main shaft to an extended position in which the shuttle element extends distally beyond the distal end of the main shaft, wherein the electrode shanks are more flexible than the shuttle elements, and each shuttle element is connected to the electrode shanks of the plurality of electrode shanks to move the electrode shanks from the retracted position to the extended position, and the high - density brain electrode assembly is configured to distribute the distal ends of the electrode shanks in a surface area larger than the maximum cross - sectional area of the distal end of the main shaft in a plane perpendicular to the longitudinal axis of the main shaft in the extended position.

[0012] The high-density brain electrode assembly is configured to enable reading and / or stimulation of non-superficial brain tissue, such as deep brain tissue like the LGN. The high-density brain electrode assembly includes a main shaft that penetrates the brain to a desired implantation position at a predetermined depth within the brain. During penetration of the main shaft into the brain, the electrode shank and the shuttle element are positioned in a retracted position where the electrode shank and the shuttle element are drawn into the main shaft. When the main shaft is positioned at the desired implantation position, the shuttle element and the electrode shank may be moved from the retracted position to an extended position to position the electrical contact of the electrode shank within the tissue of interest, such as the LGN.

[0013] The electrode shank is more flexible (softer) than the shuttle element. Each shuttle element is connected to one of the electrode shanks, for example, at their respective distal ends, such that the shuttle element can be used to push the electrode shank from the retracted position to the extended position. When the electrode shank is positioned in the extended position, the connection between the shuttle element and the electrode shank is released, and the shuttle element can return to the retracted position while the electrode shank remains in the extended position.

[0014] The connection between the shuttle element and the electrode shank may be a releasable connection. Such a releasable connection may be released by an active release step or as a result of the shuttle element moving from the extended position to the retracted position. The releasable connection may also be a cerebrospinal fluid-soluble adhesive, such as one based on polyethylene glycol. That is, after the electrode shank has moved to the extended position, the adhesive dissolves, thereby releasing the connection between the electrode shank and the corresponding shuttle element and enabling the shuttle element to be safely retracted to the retracted position. Polyethylene glycol can dissolve, for example, within seconds to minutes after contacting cerebrospinal fluid.

[0015] In another embodiment, the shuttle element can be arranged to at least partially lose its rigidity after implantation, for example, by using silk fibroin that can have a rigidity that decreases after implantation into the brain. In such an embodiment, the shuttle element and the electrode shank can be combined into a single element that substantially forms a releasable connection to the electrode shank that is released when the shuttle element loses its rigidity.

[0016] According to the combination of the shuttle element and the electrode shank, when the combination of the shuttle element and the electrode shank moves to the extended position, the electrode shank can be placed into the desired tissue, thereby eliminating the need to provide a relatively rigid electrode shank and providing sufficient rigidity of the shuttle element, i.e., sufficient rigidity for pushability. The flexibility of the electrode shank after release of the shuttle element, and optionally the movement back to the retracted position, provides the following advantages: the relative movement between the tissue in which the electrode shank is placed and the tissue or bone holding the main shaft is not substantially impeded by the rigidity of the electrode shank and does not lead to tissue damage and / or gliosis.

[0017] The high-density brain electrode assembly is arranged to distribute the distal ends of the electrode shanks over a surface area in a plane perpendicular to the longitudinal axis of the main shaft that is larger than the maximum cross-section of the distal end of the main shaft perpendicular to the longitudinal axis of the main shaft.

[0018] With this configuration, the electrode shank can be guided through a bundle of small-diameter guide lumens arranged within the main shaft towards a non-superficial brain position. On the other hand, at the distal end of the main shaft, the electrode shank spreads, for example, in a conical shape and is distributed over a surface area larger than the cross-section of the distal end of the main shaft. The surface area over which the electrode shanks can be distributed in a direction perpendicular to the longitudinal axis of the main shaft may be at least twice, for example, at least five times the surface area of the cross-section of the distal end of the main shaft. Thereby, a distribution of electrical contacts of the electrode shanks can be brought about over a relatively large volume as compared to the cross-section of the distal end of the main shaft. At the same time, the actual volume of the brain tissue, the actual volume of the brain tissue over which a large number of electrical contacts can be distributed by the electrode shanks is small, for example, 50 mm 3 to 250 mm 3 and relatively high-density electrical contacts are brought about, distributed among the respective volumes.

[0019] In one embodiment, the high-density brain electrode assembly is arranged to distribute the distal ends of the electrode shanks over a surface area in a plane perpendicular to the longitudinal axis of the main shaft, which is larger than the maximum cross-section of the implantable portion of the main shaft perpendicular to the longitudinal axis of the main shaft. For example, at least twice, at least five times the surface area of the cross-section of the implantable portion of the main shaft. The implantable portion includes the portion of the main shaft that can extend through the brain tissue after implantation of the main shaft.

[0020] In one embodiment, one or more of the plurality of guide lumens have a non-zero exit angle with respect to the longitudinal axis of the main shaft, whereby, at the extension position, the electrode shanks extending from each guide lumen spread away from the longitudinal axis. In order to branch the electrode shanks away from the longitudinal axis of the main shaft at the extension position, the exit angle of the guide lumen at the distal end of the main shaft can be arranged at an angle with respect to the longitudinal axis of the main shaft, that is, a non-zero angle.

[0021] The distal opening of the guide lumen located further away from the longitudinal axis of the main shaft has a larger exit angle than the distal opening of the guide lumen closer to the longitudinal axis, and a desired distribution of the electrode shanks within the volume of the brain tissue in which the electrode shanks extend may be obtained. The exit angle of the guide lumen may be used, for example, to vary the density and / or spacing of the electrode shanks within the volume so as to optimize the phosphine coating rate within this volume.

[0022] The distal opening of the guide lumen may be arranged in two or more concentric circles arranged concentrically with respect to the longitudinal axis of the main shaft, and the distal opening of the inner concentric circle has a smaller exit angle with respect to the longitudinal axis of the main shaft compared to the exit angle of the distal opening of the outer concentric circle. Any other suitable configuration can also be applied.

[0023] A guide block may be provided at the distal end of the main shaft, and the guide block forms an angled distal opening disposed at the distal end of the guide lumen. The guide block may be made of any suitable material such as a ceramic, metal, or polymer material, and may be formed by 3D printing. Since the guide block can be used to fan out the electrode shanks in the problematic brain volume, the guide block may also be referred to as a fountain block.

[0024] In one embodiment, the guide lumen is formed by a tube or tunnel extending from the proximal end to the distal end of the main shaft. A bundle of tubes may be provided to at least partially form the shuttle element and a plurality of guide lumens in which the electrode shanks extend. On the distal side of the tube, the tube may be connected to each guide lumen disposed in the guide block. Alternatively, the tubes may be arranged at a desired exit angle.

[0025] In one embodiment, one or more of the shuttle elements may be preformed into a non-linear structure, at least at its distal portion, and adapted to assume a more linear shape in response to the application of force thereto. Such shuttle elements, when disposed within their respective guide lumens, assume a more straight structure, and each shuttle element may assume a partially non-linear structure when moved to an extended position and extending at least partially from the distal end of the main shaft. This preformed non-linear structure can facilitate spreading at least a portion of the shuttle element in a fan-like manner to a cross-section larger than the maximum cross-section of the distal end of the main shaft perpendicular to the longitudinal axis of the main shaft. The preformed shuttle elements having a non-linear structure may be used in combination or as an alternative due to the non-zero exit angle of the guide lumen.

[0026] The electrode shank may be formed as a thin strip having a series of electrical contacts along at least a portion extending distally from the distal end of the main shaft in the extended position. By disposing a plurality of electrode shanks within a desired non-superficial brain tissue, each electrode shank has a plurality of electrical contacts along the length of the electrode shank, thereby forming a three-dimensional array or grid of high-density electrical contacts that enables effective stimulation and / or recording of non-superficial, e.g., deep brain tissue.

[0027] In one embodiment, the electrode shank is a strip having a thickness in the range of 0.1 μm to 40 μm, such as in the range of 1 μm to 20 μm. The strip can have a width in the range of 1 μm to 250 μm, such as in the range of 25 μm to 150 μm. The strip may be made of any flexible and tissue biocompatible material such as polyimide or SU-8. The electrical contacts can be made of a material capable of passing current through the tissue, such as iridium oxide, microstructured platinum, platinum-iridium, PEDOT, or titanium nitride. Each electrode shank can have, for example, 5 to 100 electrical contacts, such as 10 to 50 electrical contacts.

[0028] In one embodiment, the proximal ends of the electrode shanks are connected to each other. By connecting the electrode shanks to each other, the conductive wires to each of the electrical contacts can be combined into a single bundle of conductive wires. The conductive wires can be provided using printing or etching techniques available from semiconductor engineering.

[0029] In one embodiment, the electrode shanks may be connected to each other by electrical lead elements. The electrical lead elements can provide support for the electrical wiring to each of the electrical contacts on the electrode shanks. The conductive wires can be provided using printing or etching techniques available from semiconductor engineering.

[0030] In one embodiment, the electrode shanks and the electrical lead elements are integrally cut from a single sheet material, such as a film material provided with electrical leads.

[0031] In one embodiment, the main shaft includes at least 10, for example at least 20, guide lumens. The high-density brain electrode assembly is configured for the deployment of a plurality of electrode shanks in non-superficial brain tissue.

[0032] In one embodiment, each guide lumen is arranged to guide one electrode shank and one shuttle element. By providing individual guide lumens for each combination of the electrode shank and the shuttle element, the movement of the combination of the electrode shank and the shuttle element from the retracted position to the extended position, and the associated implantation path of the electrode shank to the extended position can be controlled more precisely.

[0033] In one embodiment, the guide lumen has an inner diameter in the range of 50 μm to 500 μm, for example 80 μm to 250 μm.

[0034] In one embodiment, each electrode shank comprises an opening at or near its distal end, and each shuttle element comprises a tapered end that extends at least partially through the opening near or at its distal end so as to provide a releasable connection between the electrode shank and the shuttle element. Such a combination of the opening and the tapered end provides a simple and effective way to provide a releasable connection that automatically releases when the shuttle element is retracted toward the retracted position.

[0035] In one embodiment, the extendable portion of the electrode shank extends in the extended position in the range of 0.5 mm to 50 mm, for example, in the range of 5 mm to 30 mm, from the distal end of the main shaft.

[0036] In one embodiment, the electrode assembly comprises an insert element connected to the proximal end of the shuttle element and configured to simultaneously move the shuttle element between the retracted position and the extended position. The insert element may extend proximally from the main shaft for manually or mechanically operating the insert element. After the electrode shank has moved from the retracted position to the extended position, the insert element may be completely removable from the main shaft together with the shuttle element or may remain in the retracted position. As an alternative to an insert element connected to all shuttle elements, each shuttle element may be individually movable between the retracted position and the extended position and may be removable from the main shaft after moving its respective electrode shank to the extended position. Also, a plurality of insert elements connected to a subgroup of the shuttle elements may be provided.

[0037] In one embodiment, the shuttle element comprises a metal such as tungsten. The rigidity of the shuttle element is selected such that the electrode shanks can be simultaneously positioned at desired positions within the non-superficial brain tissue, for example, by being mechanically driven by hand force or by a suitable tool.

[0038] In one embodiment, the main shaft has a diameter ranging from 0.5 mm to 5 mm. The main shaft is configured to accommodate a plurality of guide lumens, and an electrode shank and a shuttle element are disposed in each of the plurality of guide lumens. The main shaft may have a length in the range of 1 cm to 20 cm, for example, in the range of 3 cm to 12 cm.

[0039] The present invention is also a neural prosthetic system for substituting a mammalian sensory modality by electrical stimulation of a non - superficial brain region of the mammal corresponding to the neural modality to be substituted, the system comprising, for use by a mammal, at least one sensor configured to generate a data feed by detecting the neural modality to be substituted, at least one high - density brain electrode assembly according to any one of claims 1 to 13, a drive unit configured to electrically drive the electrical contacts of the high - density brain electrode assembly to stimulate the non - superficial brain region, and a processing unit configured to analyze the detected data feed to provide a stimulation pattern for electrically driving the electrical contacts of the high - density brain electrode assembly corresponding to a subset of positions within the non - superficial brain region for substituting the sensory modality.

[0040] In one embodiment, the neural prosthetic system is configured to substitute vision in a non - superficial brain region of a mammal, and the at least one sensor comprises at least one portable imaging unit configured to capture an image and generate a captured image data feed.

[0041] In one embodiment, the system can include a switching device for sending one or more stimulation signals of the drive unit to a subset of electrical contacts located within the non - superficial brain region that provides the functional coverage of the sensory modality. The switching device enables the system to connect multiple (groups) of electrode shanks or their specific electrical contacts to a single signal generator. Thus, it is not necessary to provide a signal generator for each electrical contact, and only a fairly small amount, preferably corresponding to the number of different stimulation signals that the drive unit has to generate, is required.

[0042] The present invention further relates to a method for substituting a mammalian sensory modality by electrical stimulation of a non - superficial brain region of a mammal using at least one high - density brain electrode assembly according to any one of claims 1 to 13, the method comprising: implanting the main shaft of the high - density brain electrode assembly at a desired implantation position; moving a plurality of shuttle elements from a retracted position to an extended position to move each electrode shank from a retracted position to an extended position and position the electrical contacts at their implantation positions; detecting, with a sensor, the neural modality to be substituted to generate detection data; electrically driving the electrical contacts of the high - density brain electrode assembly for stimulating the non - superficial brain region; and analyzing the detected data feed to provide a stimulation pattern for electrically driving the electrical contacts of the high - density brain electrode assembly corresponding to a subset of positions within the non - superficial brain region for substituting the sensory modality.

Brief Description of the Drawings

[0043]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 5C

Figure 6

Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0044] FIG. 1 schematically shows a high-density brain electrode assembly 1 for reading and / or stimulating non-superficial brain tissue. The electrode assembly 1 is arranged to be implanted in the brain of a mammal and has a plurality of electrode shanks each having a plurality of electrical contacts disposed in a region of interest of the non-superficial brain, particularly a region of interest in the deep brain, such as the lateral geniculate nucleus (LGN) of the human thalamus, to provide electrical reading and / or stimulation in each non-superficial brain region. The electrode assembly 1 includes an elongated main shaft 2 having a proximal end 3 and a distal end 4. A plurality of electrode shanks are disposed in a retracted position within the main shaft 2, and the electrode shanks are mainly housed within the main shaft 2 and do not extend beyond the distal end 4 of the main shaft 2.

[0045] Figure 2 schematically shows the electrode assembly 1 of FIG. 1 in a transplanted state. The electrode shank 5 extends to an extended position where the electrode shank 5 extends from the distal end 4 of the main shaft 2. In the implanted state, the electrical contacts of the electrode shank 5 are arranged to contact the tissue into which the electrode shank 5 is implanted. The electrode shank 5 is configured as a flexible strip so as to be able to accommodate relative movement within a certain range of movement between the main shaft 2 and the electrical contacts of the electrode shank 5. Thus, the electrode shank 5 can move relatively freely with respect to the main shaft 2, whereby the electrode shank 5 can follow the movement of the tissue into which the electrode shank 5 is implanted without requiring the main shaft to follow the movement of the electrode shank 5. However, the use of the flexible electrode shank 5 makes it more difficult to implant the electrode shank through the tissue into which the electrode shank 5 is implanted. To effectively implant the electrode shank 2 in the desired position, a shuttle element is used as described below.

[0046] The electrode assembly 1 is arranged to distribute the distal end of the electrode shank in a surface area Ai that is larger than the maximum cross-sectional area As in a cross-section perpendicular to the longitudinal axis A-A of the main shaft 2 in a plane perpendicular to the longitudinal axis A-A of the main shaft 2. Thereby, the electrode shank 5 extends from the distal end 4 of the main shaft 2 to a surface area Ai that is larger than the cross-section As of the main shaft 2. The surface area Ai in which the electrode shank 5 is distributed may be at least twice, for example, at least five times the surface area As of the cross-section of the main shaft 2. As a result, the electrode shank 5 extends into a conical volume, and the electrical contacts provided on the electrode shank form a three-dimensional grid of electrical contacts within the tissue into which the electrode shank 5 is implanted.

[0047] The extendable portion of the electrode shank 5, i.e., the portion extending from the distal end 4 of the main shaft to the extended position, can have a length in the range of 0.5 mm to 30 mm, for example, 10 mm to 20 mm. The diameter of the main shaft 2 can be in the range of, for example, 1 mm to 10 mm. The dimensions can also depend on the application. For example, an electrode assembly for a mouse can have considerably smaller dimensions than an electrode assembly for a human.

[0048] Figure 3 shows a cross-sectional view of the distal portion of the electrode assembly 1. The main shaft 2 includes a plurality of guide lumens 6 that extend primarily in the longitudinal direction of the main shaft, i.e., parallel to the longitudinal axis A-A of the main shaft 2. Each guide lumen 6 houses an electrode shank 5 and a shuttle element 7.

[0049] The shuttle element 7 is an elongated element, for example, a wire made of a metal such as tungsten, silicon, or another suitable material. The shuttle element 7 is less flexible than the electrode shank 5. The shuttle element 7 is movable between a retracted position as shown in Figure 3 and an extended position in which the shuttle element extends at least partially out of the distal opening of the guide lumen 6.

[0050] The electrode shanks 5 are connected to each other at their proximal ends by electrical lead elements 8. The electrode shanks 5 and the electrical lead elements 8 may be cut as an integral part from a sheet of material such as a film material provided with electrical leads. The electrical leads can be produced using printing techniques or etching techniques, etc. The electrical lead elements 8 may be wound or folded to create a compact form.

[0051] In the embodiment of FIG. 3, the shuttle element 7 is connected to the insert element 9 at its proximal end. The insert element 9 facilitates the simultaneous movement of the shuttle element 7 between a retracted position and an extended position. The insert element 9 extends proximally from the proximal end 3 of the main shaft 2 to enable the operation of the insert element 9 (see FIGS. 1 and 2). In an alternative form, individual insert elements may be provided for each shuttle element 7 to facilitate the individual movement of the shuttle elements 7. Two or more insert elements may be provided, each connected to a subgroup of the shuttle elements 7 to facilitate the movement of the shuttle elements for each subgroup.

[0052] The distal end of the electrode shank 5 is releasably connected to the distal end of the shuttle element 7 by a releasable connection 10. In the illustrated embodiment, the releasable connection 10 is constituted by a tapered portion of the distal end of the shuttle element 7 extending through an opening at the distal end of the electrode shank 5. As shown in FIGS. 5A to 5C, the releasable connection 10 is provided such that the movement of the shuttle element 7 from the retracted position to the extended position is effected along the electrode shank 5 from the retracted position to the extended position. In the extended position, the releasable connection 10 may be released, and while the electrode shank 5 remains in the extended position, the shuttle element 7 may be returned to the retracted position.

[0053] A guide block 11 is provided at the distal end 4 of the main shaft 2. The guide block 11 includes at least the distal portion of the guide lumen 6 and forms a distal opening at the distal end 4 of the main shaft 2.

[0054] Figure 4 shows a cross-section B-B of the main shaft 2 and shows an example of the distribution of the guide lumen 6 across the cross-section of the main shaft. In this embodiment, the main shaft 2 is provided with 35 guide lumens 6 respectively arranged to guide one assembly of the electrode shank 5 and the shuttle element 7. The guide lumen terminates within the guide block 11. The number of guide lumens may depend on the application. In practice, for human application, the number of guide lumens may be at least 10, for example at least 20 to 50 or more, and each guide lumen 6 houses the electrode shank 5 and the shuttle element 7. The guide lumen 6 can have an inner diameter in the range of 50 μm to 500 μm, for example in the range of 80 μm to 250 μm.

[0055] The guide lumen 6 includes one central guide lumen 6 arranged on the longitudinal axis A-A of the main shaft 2. The other guide lumens 6 are arranged in three concentric circles around the central guide lumen 6. The three concentric circles include an inner circle with 6 guide lumens 6, a central circle with 12 guide lumens 6, and an outer circle with 16 guide lumens 6.

[0056] As can be understood from FIG. 3, the exit angle of the central guide lumen 6 is zero, that is, the extending direction is parallel to the longitudinal axis A-A. The other guide lumens 6 have a non-zero exit angle with respect to the longitudinal axis A-A of the main shaft 2. In particular, as shown in FIG. 3, the distal opening of the inner circle has a first exit angle Di, the distal opening of the central circle has a second exit angle Dm, the distal opening of the outer circle has a third exit angle Do, the third exit angle Do is larger than the second exit angle Dm, and the second exit angle Dm is larger than the first exit angle Di.

[0057] The exit angles Di, Dm, Do of the distal openings facilitate the electrode shank 5 and, together with it, the shuttle element 7 to extend outward at an angle from the distal end of the main shaft 2. Thereby, as shown in FIG. 2, a fan-shaped conical structure of the electrode shank 5 is formed after embedding.

[0058] In the illustrated embodiment, the exit angles of one of the inner circle, the central circle, and the outer circle, i.e., the first exit angle Di of the inner circle, the second exit angle Dm of the central circle, and the third exit angle Do of the outer circle, are all the same. Generally, in order to obtain an appropriate distribution of electrical contacts within the tissue in which the electrode shank 5 is implanted, it may be advantageous to provide a larger exit angle for the distal openings disposed away from the longitudinal axis A-A.

[0059] In other embodiments, configurations in which the exit angle of each distal opening can vary, or other configurations in which the distal openings are not arranged in two or more concentric circles are also possible. For example, any configuration configured to spread at least a part of the distal end of the electrode shank 5 over a surface area larger than the cross section of the main shaft 2 can be used.

[0060] One or more of the shuttle elements 7 may be preformed into a non-linear structure, at least at their distal ends, and adapted to become a more linear structure in response to the application of a force thereto. This preformed non-linear configuration of the shuttle element 7 may facilitate the fanning out of one or more shuttle elements 7 into a cross section Ai larger than the maximum cross section As of the distal end 4 of the main shaft 2. The preformed shuttle element 7 having a non-linear configuration can be used in combination with or as an alternative to the non-zero exit angle of the guide lumen 6.

[0061] Figures 5A through 5C schematically illustrate the steps of implanting a single electrode shank 5 having electrical contacts 12 into the implant position.

[0062] As shown in FIG. 3, when the insert element 9 is connected to a plurality of shuttle elements 7, all of these shuttle elements 7 are simultaneously moved by the movement of the insert element 9. For simplicity, only one guide lumen 6 having one electrode shank 5 and one shuttle element 7 is shown in FIGS. 5A through 5C.

[0063] Figure 5A shows the electrode shank 5 and the shuttle element 7 in the retracted position. At this retracted position shown in Figure 5A, the electrode shank 5 and the shuttle element 7 do not extend beyond the distal end 4 of the main shaft 2.

[0064] Once the main shaft 2 is positioned at the appropriate implantation location within the brain, the shuttle element 7 can be moved from the retracted position to the extended position by moving the insert element 9 towards the distal end 4 of the main shaft. The movement of the shuttle element 7 causes the electrode shank 5 to move by means of a releasable connection 10 at the distal ends of the electrode shank 5 and the shuttle element 7. The releasable connection 10 is formed by a tapered portion 13 at the distal end of the shuttle element 7 that extends through an opening 14 at the distal end of the electrode shank 5. This releasable connection 10 is automatically released when the shuttle element 7 is returned to the retracted position.

[0065] Figure 5B shows the electrode shank 5 and the shuttle element 7 in the extended position where an extendable portion having the electrical contact 12 extends from the distal end 4 of the main shaft 2. The distal opening of the guide lumen 6 shown from Figure 5A to Figure 5C has an exit angle of zero, and as a result, the electrode shank 5 and the shuttle element 7 extend parallel to the longitudinal axis A-A of the main shaft. If the exit angle is not zero, the extended portion of the electrode shank will extend along a path angled with respect to the longitudinal axis of the main shaft.

[0066] When the electrode shank 5 is in the extended position, the shuttle element 7 can be returned to the retracted position by operation of the insert element 9. To enable this movement, the releasable connection 10 between the electrode shank 5 and the shuttle element 7 needs to be released without pulling back the electrode shank 5.

[0067] FIG. 5C shows the shuttle element 7 with the electrode shank 5 remaining in the extended position and having returned to the retracted position. The insert element 9 and the shuttle element 7 connected to the insert element 9 can be partially or fully removed from the main shaft 2 since, at least in the illustrated embodiment, they are only used for embedding in the desired brain tissue.

[0068] FIG. 6 shows a cross-sectional view of an alternative form of a high-density brain electrode assembly for reading and / or stimulating non-superficial brain tissue. In this embodiment, each shuttle element 7 is provided with an individual insert element 9 to facilitate the individual movement of each shuttle element 7 between the retracted position and the extended position. Further, the releasable connection 10 between the electrode shank 5 and the shuttle element 7 is formed by a cerebrospinal fluid-soluble adhesive, such as polyethylene glycol. After the movement of the electrode shank 5 to the extended position, the adhesive dissolves, thereby releasing the connection between the electrode shank 5 and the corresponding shuttle element 7 and enabling the safe retraction of the shuttle element to the retracted position.

[0069] In another embodiment, the shuttle element 7 may be provided to at least partially lose its rigidity after implantation, for example, by using silk fibroins that may have a decreasing rigidity after implantation into the brain. In such an embodiment, the shuttle element 7 and the electrode shank 5 may be combined into a single element that substantially releases the electrode shank 5 when the shuttle element 7 loses its rigidity.

[0070] FIG. 7 shows the electrode assembly 1 of FIGS. 1 and 2 implanted in the LGN of the thalamus 50 of a human brain. The electrode assembly 1 can be used as a stimulating electrode 1 in a neuroprosthetic system 100 for replacing a patient's sensory modality by electrical stimulation of a non-superficial region of the patient's brain corresponding to the neural modality to be replaced.

[0071] More specifically, the neuroprosthetic system 100 is configured to replace vision in the deep brain regions of a mammal by applying electrical stimulation to the LGN where the electrode shank 5 extends. For each LGN, a high-density brain electrode assembly 1 can be implanted in the respective LGN.

[0072] The neuroprosthetic system 100 can further include at least one sensor 101, a processing unit 102, and a driving unit 103. The at least one sensor 101 includes at least one portable imaging unit configured to capture an image and generate a captured image data feed.

[0073] The captured image data feed can be supplied to the processing unit 102 as a sensed data feed. The processing unit 102 is configured to analyze the sensed data feed and provide a stimulation pattern for electrically driving the electrodes of the electrode unit corresponding to a subset of the positions within the deep brain region to replace the sensory modality.

[0074] The driving unit 103 is configured to actually electrically drive the electrical contacts of the deep brain stimulation electrode assembly 1 to stimulate the respective stimulation positions within the LGN.

Claims

**Claim 1** An elongated main shaft having a plurality of guide lumens, the guide lumens extending to the distal end of the main shaft, the main shaft, and A plurality of elongated electrode shanks, each electrode shank having a plurality of electrical contacts, passing through one of the plurality of guide lumens, and each electrode shank being movable from a retracted position retracted into the main shaft to an extended position extending distally beyond the distal end of the main shaft, a plurality of elongated electrode shanks, and A plurality of shuttle elements, each shuttle element passing through one of the plurality of guide lumens and being movable from a retracted position retracted at the distal end of the main shaft to an extended position extending distally beyond the distal end of the main shaft, a plurality of shuttle elements, and A high-density brain electrode assembly comprising The electrode shank is more flexible than the shuttle element, and each shuttle element is connected to one of the plurality of electrode shanks to move each electrode shank from the retracted position to the extended position, The high-density brain electrode assembly is configured to distribute the distal ends of the electrode shanks in a surface area larger than the maximum cross-sectional area of the distal end of the main shaft in a plane perpendicular to the longitudinal axis of the main shaft, High-density brain electrode assembly. **Claim 2** One or more of the plurality of guide lumens have a non-zero exit angle with respect to the longitudinal axis of the main shaft such that the electrode shank extends outward from the longitudinal axis so as to extend from one or more of the guide lumens at the extended position, The high-density brain electrode assembly according to claim 1. **Claim 3** The guide lumen is at least partially formed by a guide tube or tunnel passing through the main shaft, The high-density brain electrode assembly according to claim 1 or 2. **Claim 4** The proximal ends of the plurality of electrode shanks are interconnected by electrical lead elements, The high-density brain electrode assembly according to any one of claims 1 to 3. **Claim 5** The electrode shank and the electrical lead element are integrally cut from a single sheet material, The high-density brain electrode assembly according to claim 4. **Claim 6** Each guide lumen guides one of the electrode shanks and one of the shuttle elements. The high-density brain electrode assembly according to any one of claims 1 to 5. **Claim 7** The main shaft has at least 10 of the guide lumens. The high-density brain electrode assembly according to any one of claims 1 to 6. **Claim 8** The inner diameter of the guide lumen is from 50 μm to 500 μm. The high-density brain electrode assembly according to any one of claims 1 to 7. **Claim 9** The distal end of each shuttle element is releasably coupled to the distal end of the corresponding electrode shank. The high-density brain electrode assembly according to any one of claims 1 to 8. **Claim 10** Each shuttle element is configured to at least partially lose rigidity after implantation. The high-density brain electrode assembly according to any one of claims 1 to 8. **Claim 11** The extendable portion of each electrode shank extends at least 0.5 mm distally from the distal end of the main shaft at the extended position. The high-density brain electrode assembly according to any one of claims 1 to 10. **Claim 12** The electrode assembly has an insert element. The insert element is connected to the proximal ends of a plurality of the shuttle elements and is configured to simultaneously move the shuttle elements between the retracted position and the extended position. The high-density brain electrode assembly according to any one of claims 1 to 11. **Claim 13** The diameter of the main shaft is from 0.2 mm to 10 mm. The high-density brain electrode assembly according to any one of claims 1 to 12. **Claim 14** A neuroprosthetic system for replacing a mammalian sensory modality by electrical stimulation of a non-superficial brain region corresponding to the sensory modality, At least one sensor used by the mammal, the at least one sensor detecting the sensory modality to be replaced and generating a data feed, At least one of the high-density brain electrode assemblies according to any one of claims 1 to 13, A drive unit provided to electrically drive the electrical contacts of the high-density brain electrode assembly to stimulate the non-superficial brain region. To replace the sensory modality, a processing unit provided to analyze the detected data feed to provide a stimulation pattern for electrically driving the electrical contacts of a high-density brain electrode assembly corresponding to a subset of the locations of the non-superficial brain regions, A neuroprosthetic system comprising. **Claim 15** configured to replace visual perception in the non-superficial brain region of the mammal, wherein the at least one sensor has at least one portable imaging unit for capturing an image and generating a data feed of the captured image. The neuroprosthetic system according to claim 14.

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