SSVEP (Steady-State Visual Evoked Potential)-based brain-computer interface stimulation modulation method, system and device and medium

Abstract

The invention provides a brain-computer interface stimulation modulation method, system and device based on SSVEP (Steady-State Visual Evoked Potential) and a medium. The method comprises the following steps: acquiring a preset coding sequence set, a stimulation frequency set and a stimulation normal form; the coding sequence set comprises a plurality of coding sequences; the coding sequence comprises a plurality of code elements, and the code elements correspond to the brightness amplitude depth coefficient; the stimulation frequency set comprises a plurality of stimulation frequencies; the stimulation normal form is used for modulating the brightness amplitude depth and the flicker frequency of the visual stimulation based on the coding sequence and the stimulation frequency; generating a coded stimulation combination of the coded sequence and the stimulation frequency based on the coded sequence and the stimulation frequency; and modulating the visual stimulation corresponding to each stimulation block by using a stimulation normal form based on the coded stimulation combination. According to the SSVEP-based brain-computer interface stimulation modulation method, system and device and the medium, the number of stimulation targets is increased, and meanwhile, the comfort degree when a user watches visual stimulation is improved.

Description

Technical Field

[0001] The present application belongs to the field of brain-computer interface technology, and in particular, relates to a brain-computer interface stimulation modulation method, system, device and medium based on SSVEP. Background Art

[0002] Steady-State Visual Evoked Potentials (SSVEP) is a neural response of the brain to periodic visual stimulation. When the visual system receives regularly changing visual stimulation, certain areas of the brain will produce electrical activity corresponding to the visual stimulation (usually presented in the form of stimulation blocks).

[0003] At present, SSVEP is widely used in the field of brain computer interface (Brain Computer Interface, BCI), that is, based on the SSVEP EEG response signals, brain commands of paralyzed patients or people with motor dysfunction are extracted, and external devices are controlled or communicated with the outside world based on the brain commands. For example, users form EEG response signals corresponding to each stimulation block by looking at different stimulation blocks on the screen, thereby generating corresponding control commands, and control external devices such as wheelchairs or prostheses based on different control commands. With the increasing demand for high communication rates and complex control tasks, existing BCI technologies have adopted a stimulation paradigm constructed by a stimulation modulation method that combines frequency and phase, which has expanded the stimulation block display format while improving coding efficiency. The existing stimulation block display format usually presents corresponding visual stimuli according to a preset brightness amplitude depth, according to different combinations of stimulation frequencies and phases, that is, at different flickering frequencies and times. However, since the brightness amplitude depth of visual stimuli modulated by existing stimulation modulation methods are all fixed values ​​(usually high brightness amplitude depth), long-term staring at such visual stimuli can easily cause visual and mental fatigue in users, affect the amplitude and signal-to-noise ratio of EEG response signals, and reduce the classification accuracy of EEG response signals.

[0004] Based on this, how to provide a stimulation modulation method with variable brightness amplitude depth of visual stimulation on the basis of expanding the visual stimulation display form, so as to reduce the visual and mental fatigue of users is an important issue that needs to be solved urgently. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a brain-computer interface stimulation modulation method based on SSVEP, which is used to solve the problem that the visual stimulation modulated by the existing brain-computer interface stimulation modulation method based on SSVEP maintains a fixed brightness amplitude depth, which easily causes visual and mental fatigue of the user.

[0006] To achieve the above-mentioned purpose and other related purposes, the present invention provides a brain-computer interface stimulation modulation method based on SSVEP, comprising the following steps:

[0007] Acquire a preset coding sequence set, a stimulation frequency set and a stimulation paradigm; the coding sequence set includes a plurality of coding sequences; the coding sequence includes a plurality of code elements, and the code elements correspond to brightness amplitude depth coefficients; the stimulation frequency set includes a plurality of stimulation frequencies; the stimulation paradigm is used to modulate the brightness amplitude depth and flicker frequency of visual stimulation based on the coding sequence and the stimulation frequency; wherein the brightness amplitude depth of the visual stimulation changes sinusoidally over time;

[0008] Based on the coding sequence and the stimulation frequency, generating a coding stimulation combination of the coding sequence and the stimulation frequency; a single coding stimulation combination is a combination of a single coding sequence and a single stimulation frequency;

[0009] Based on the coded stimulus combination, the visual stimulus corresponding to each stimulus block is modulated using the stimulus paradigm.

[0010] In one embodiment of the present invention, the method of constructing the stimulation paradigm includes:

[0011] Amplitude keying is adopted to control the amplitude of the sine wave using the brightness amplitude depth, and the stimulation frequency is taken as the number of cycles of the sine wave per unit time to construct the stimulation paradigm so as to load the signal onto the sine wave.

[0012] In one embodiment of the present invention, generating a coded stimulation combination of the coded sequence and the stimulation frequency based on the coded sequence and the stimulation frequency includes:

[0013] According to the coding sequence and the stimulation frequency, all possible coding stimulation combinations between the coding sequence and the stimulation frequency are generated.

[0014] In one embodiment of the present invention, based on the coded stimulus combination, using the stimulus paradigm, modulating the visual stimulus corresponding to each stimulus block includes:

[0015] Based on each of the coded stimulus combinations, the corresponding stimulus blocks are generated respectively; based on the coded stimulus combinations, the visual stimulus corresponding to each of the stimulus blocks is modulated according to the stimulus paradigm.

[0016] In one embodiment of the present invention, when the coding sequence is encoded using a binary coding method and the total number of code elements in the coding sequence is an even number, the number of code elements of the two types of code elements in the coding sequence is equal.

[0017] In one embodiment of the present invention, the stimulation blocks with the same stimulation frequency and / or the same coding sequence are arranged to be non-adjacent.

[0018] In one embodiment of the present invention, after modulating the visual stimulus corresponding to each of the stimulus blocks, the method further includes:

[0019] Each of the stimulation blocks is presented as a corresponding visual stimulus, so that the subject generates an electroencephalographic response signal corresponding to the target stimulation block based on the target stimulation block.

[0020] Correspondingly, the present invention provides a brain-computer interface stimulation modulation system based on SSVEP, comprising:

[0021] An acquisition module is used to acquire a preset coding sequence set, a stimulation frequency set and a stimulation paradigm; the coding sequence set includes a plurality of coding sequences; the coding sequence includes a plurality of code elements, and the code elements correspond to brightness amplitude depth coefficients; the stimulation frequency set includes a plurality of stimulation frequencies; the stimulation paradigm is used to modulate the brightness amplitude depth and flicker frequency of visual stimulation based on the coding sequence and the stimulation frequency; wherein the brightness amplitude depth of the visual stimulation changes sinusoidally over time;

[0022] A coding stimulation combination generating module, used for generating a coding stimulation combination of the coding sequence and the stimulation frequency based on the coding sequence and the stimulation frequency; a single coding stimulation combination is a combination of a single coding sequence and a single stimulation frequency;

[0023] The stimulus modulation module is used to modulate the visual stimulus corresponding to each stimulus block based on the coded stimulus combination and using the stimulus paradigm.

[0024] Correspondingly, the present invention provides a computer device, comprising:

[0025] Memory for storing computer programs;

[0026] A processor is used to execute the computer program stored in the memory so that the device performs the SSVEP-based brain-computer interface stimulation modulation method as described above.

[0027] Correspondingly, the present invention provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the SSVEP-based brain-computer interface stimulation modulation method as described above.

[0028] As described above, the present application provides a brain-computer interface stimulation modulation method, system, device and medium based on SSVEP, which has at least the following beneficial effects:

[0029] By obtaining a preset stimulation paradigm, a coding sequence set and a stimulation frequency set, determining the number of stimulation blocks based on the number of coding sequences and the number of stimulation frequencies, and modulating the brightness amplitude depth corresponding to the stimulation blocks according to the stimulation paradigm to produce a sinusoidal change in visual stimulation, the method not only expands the display form of the stimulation blocks, but also improves the comfort of the user when looking at the visual stimulation presented by the stimulation blocks, thereby reducing the user's visual and mental fatigue. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Shown is a flow chart of a SSVEP-based brain-computer interface stimulation modulation method provided in the present application in one embodiment.

[0031] Figure 2 Shown is a schematic diagram of the stimulation modulation process of a brain-computer interface stimulation modulation method based on SSVEP provided in the present application in one embodiment.

[0032] Figure 3 A schematic diagram of a coded stimulation combination generation process in an embodiment of a brain-computer interface stimulation modulation method based on SSVEP provided in the present application is shown.

[0033] Figure 4 Shown is a flow chart of a SSVEP-based brain-computer interface stimulation modulation method provided in the present application in another embodiment.

[0034] Figure 5 Shown is a schematic diagram of stimulation layout in an embodiment of a brain-computer interface stimulation modulation method based on SSVEP provided in the present application.

[0035] Figure 6 Shown is a comparison diagram of the experimental effects of the SSVEP-based brain-computer interface stimulation modulation method provided in this application in one embodiment.

[0036] Figure 7 Shown is a module structure diagram of a SSVEP-based brain-computer interface stimulation modulation system in one embodiment provided by the present application.

[0037] Figure 8 A schematic diagram of the structure of a computer device provided by the present application is shown.

[0038] Description of Reference Numerals

[0039] S1~S4, steps; 200, brain-computer interface stimulation modulation system; 201, acquisition module; 202, coded stimulation combination generation module; 203, stimulation modulation module; 300, computer device; 301, memory; 302, processor. DETAILED DESCRIPTION

[0040] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0041] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application, and thus the drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed at will, and the component layout may also be more complicated.

[0042] To facilitate the understanding of the technical solutions provided by the present application, the relevant terms in the present application are explained before the specific embodiments, as follows:

[0043] Amplitude shift keying: a modulation method that uses a baseband digital signal to control the amplitude change of the carrier, and represents the digital signal by changing the amplitude of the carrier signal.

[0044] The embodiments of the present application are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the features of the following embodiments and implementations can be combined with each other.

[0045] The following embodiments of the present application provide a brain-computer interface stimulation modulation method based on SSVEP, which obtains a stimulation paradigm, a coding sequence set and a stimulation frequency set, determines the number of stimulation blocks based on the number of coding sequences and the number of stimulation frequencies, and modulates the visual stimulation corresponding to the stimulation block based on the coding sequence and the stimulation frequency, according to the stimulation paradigm, to produce a sinusoidal change in the brightness amplitude depth. The method not only expands the display form of the stimulation block, but also improves the comfort of the user when looking at the visual stimulation presented by the stimulation block, thereby reducing the user's visual and mental fatigue.

[0046] See also Figure 1 , showing a flow chart of a SSVEP-based brain-computer interface stimulation modulation method provided by the present invention in one embodiment.

[0047] like Figure 1 As shown, in this embodiment, the SSVEP-based brain-computer interface stimulation modulation method provided by the present invention includes the following steps:

[0048] Step S1, obtaining a preset coding sequence set, stimulation frequency set and stimulation paradigm;

[0049] Among them, the coding sequence set includes several coding sequences; the coding sequence includes several code elements, which correspond to the brightness amplitude depth coefficients and are used to adjust the brightness amplitude depth of the visual stimulus; the brightness amplitude depth represents the degree of brightness change of the visual stimulus.

[0050] The stimulation frequency set includes a plurality of stimulation frequencies; the stimulation frequencies are used to regulate the flickering frequency of visual stimulation;

[0051] The stimulation paradigm is used to modulate the brightness amplitude depth and flicker frequency of the visual stimulation based on the coding sequence and the stimulation frequency; wherein the brightness amplitude depth of the visual stimulation changes sinusoidally over time.

[0052] Optionally, the stimulation paradigm is constructed in a manner including:

[0053] Amplitude keying is adopted to control the amplitude of the sine wave using the brightness amplitude depth, and the stimulation frequency is taken as the number of cycles of the sine wave per unit time to construct the stimulation paradigm so as to load the signal onto the sine wave.

[0054] Exemplarily, the stimulation paradigm is as follows:

[0055]

[0056] In the above formula, S represents the current grayscale value of the stimulus block; the sin() function is used to generate a sine wave sequence; n represents the frame sequence of the stimulus block; f represents the stimulus frequency; k represents the brightness amplitude depth coefficient; r represents the refresh rate of the stimulus display device; where, It represents the ratio between the frame sequence and the refresh rate of the stimulation display device, that is, the time the frame is displayed on the stimulation display device.

[0057] Optionally, the brightness amplitude depth coefficient takes a value of 1 or 0.5.

[0058] Optionally, the refresh rate of the stimulation display device is 60 Hz.

[0059] Optionally, the code element width of each code element in the coding sequence is 1 second; the code element width is the continuous flashing time corresponding to the code element.

[0060] Optionally, each of the code elements in the coding sequence is coded information encoded using a binary coding method based on a preset brightness amplitude depth coefficient sequence; the code elements correspond to the brightness amplitude depth coefficients in the stimulation paradigm, so as to regulate the brightness amplitude depth of the visual stimulus corresponding to the stimulation block based on the brightness amplitude depth coefficients corresponding to each of the code elements; the stimulation block is used to present the visual stimulus.

[0061] In a specific embodiment, when the coding sequence is encoded using a binary coding method and the total number of code elements in the coding sequence is an even number, the number of code elements in the two types of binary codes in the coding sequence is set to be equal, that is, the number of code elements corresponding to 0 in the binary code is set to be equal to the number of code elements corresponding to 1 in the binary code, so as to balance the overall brightness level of the visual stimulation presented by the stimulation block, so as to improve the visual comfort of the subject, reduce the pressure of the visual stimulation on the subject's eyes, and reduce visual fatigue; and brightness balance helps to reduce visual interference, improve the distinguishability of the visual stimulation, and make the brain's response to the visual stimulation clear, thereby improving the signal-to-noise ratio of the EEG response signal and the accuracy of the classification of the EEG response signal.

[0062] Optionally, the method for obtaining the stimulation frequency includes:

[0063] Obtain a preset frequency lower limit, frequency upper limit and total frequency; construct a frequency sequence based on the frequency lower limit, the frequency upper limit and the total frequency; the frequency sequence contains the same number of stimulation frequencies as the total frequency.

[0064] Optionally, the frequency sequence is an arithmetic sequence to make the frequency intervals between different visual stimuli uniform, reduce interference between the frequencies, and improve the distinguishability of each stimulation frequency in the frequency domain, so as to improve the classification accuracy of the EEG response signals corresponding to different visual stimuli.

[0065] Exemplarily, the method of constructing the frequency sequence includes:

[0066] Based on the frequency lower limit and the frequency upper limit, a frequency difference is obtained, which is the difference between the frequency upper limit and the frequency lower limit; the total frequency is subtracted by one to obtain the number of differences; based on the frequency difference and the number of differences, a tolerance is obtained, which is the ratio of the frequency difference to the number of differences; based on the frequency lower limit, the frequency upper limit and the tolerance, each stimulation frequency is obtained; wherein the stimulation frequency is greater than or equal to the frequency lower limit and less than or equal to the frequency upper limit.

[0067] Step S2, generating a coded stimulation combination of the coding sequence and the stimulation frequency based on the coding sequence and the stimulation frequency;

[0068] Among them, a single coding stimulation combination is a combination of a single coding sequence and a single stimulation frequency.

[0069] Specifically, according to the coding sequence and the stimulation frequency, all possible coding stimulation combinations between the coding sequence and the stimulation frequency are generated.

[0070] Step S3, based on the coded stimulus combination, using the stimulus paradigm, modulating the visual stimulus corresponding to each stimulus block;

[0071] Wherein, the stimulus block is used to present visual stimulation; the stimulus block and the coded stimulus combination are in a one-to-one correspondence.

[0072] Specifically, based on each of the coded stimulus combinations, the corresponding stimulus blocks are generated respectively; based on the coded stimulus combinations, according to the stimulus paradigm, the visual stimulus corresponding to each of the stimulus blocks is modulated.

[0073] In one embodiment, the step of modulating the visual stimulus corresponding to each stimulus block according to the stimulus paradigm based on the coded stimulus combination, when modulating the visual stimulus corresponding to a single stimulus block, includes:

[0074] According to the stimulation frequency in the coded stimulation combination, the flickering frequency of the visual stimulation corresponding to the stimulation block is determined; based on the coding sequence in the coded stimulation combination, according to the corresponding relationship between the code element and the brightness amplitude depth coefficient, the brightness amplitude depth of the visual stimulation presented by the stimulation block under the corresponding code element is determined;.

[0075] Exemplarily, when presenting the corresponding visual stimulus, the stimulus block regulates the brightness amplitude depth of the visual stimulus corresponding to the stimulus block according to the timing and preset code element width, in sequence according to each code element in the coding sequence, and the visual stimulus flashes at the stimulus frequency during presentation.

[0076] According to the stimulus frequency in the coded stimulus combination, the preset code element width, the visual stimulus flickering at the stimulus frequency,

[0077] Assign each of the coded stimulus combinations to the corresponding stimulus blocks, so that each of the stimulus blocks corresponds to one of the coded stimulus combinations; obtain the stimulus paradigm; and based on the coded stimulus combinations and according to the stimulus paradigm, modulate the visual stimulus corresponding to each of the stimulus blocks.

[0078] Optionally, the stimulation blocks with the same stimulation frequency and / or the same coding sequence are arranged to be non-adjacent to each other; in this embodiment, by arranging the stimulation blocks with the same stimulation frequency and / or the same coding sequence to be non-directly adjacent to each other, the interference between adjacent visual stimuli is reduced and the discrimination of the EEG response signals is improved.

[0079] For example, Figure 2As shown, the coding sequence is encoded using a binary coding method, and the code element width of each code element is 1 second. When the brightness amplitude depth coefficient takes a value of 1, it corresponds to the binary code element 1. At this time, the grayscale value corresponding to the stimulus block varies in the range of [0, 1]; when the brightness amplitude depth coefficient takes a value of 0.5, it corresponds to the binary code element 0. At this time, the grayscale value corresponding to the stimulus block varies in the range of [0.25, 0.75].

[0080] For example, Figure 3 As shown in FIG. 1 , when the coding sequence is encoded using a binary coding method and the total number of code elements in the coding sequence is 4, the total number of code elements 0 and code elements 1 in each coding sequence is set to 2. The coding sequence includes: '1010', '0101', '1001', '0110', '1100' and '0011'. Figure 3 In the above coding sequence, the six letters a, b, c, d, e, and f are used to identify the above coding sequence in sequence; the stimulation frequencies include: 10.0 Hz, 10.8 Hz, 11.6 Hz, 12.4 Hz, 13.2 Hz, and 14.0 Hz, and the six numbers 1, 2, 3, 4, 5, and 6 are used to identify the above stimulation frequencies in sequence; based on the above coding sequence and the above stimulation frequencies, the following is generated: Figure 3 The 36 coding stimulus combinations shown in the table on the right correspond to the visual stimuli modulating 36 stimulus blocks based on the coding stimulus combinations.

[0081] It should be noted that changes in the brightness, amplitude, and depth of visual stimulation will affect changes in the amplitude of the SSVEP EEG response signal. That is, the brightness, amplitude, and depth of visual stimulation can be used to modulate the amplitude of the SSVEP EEG response signal. In addition, visual stimulation with changing brightness can effectively reduce the user's visual and mental fatigue. Therefore, the present application adopts a stimulation mode with dynamically changing brightness, amplitude, and depth, which can not only expand the number of stimulation targets, but also improve the user experience.

[0082] See also Figure 4 , showing a flow chart of a brain-computer interface stimulation modulation method based on SSVEP provided by the present invention in another embodiment;

[0083] like Figure 4 As shown, in this embodiment, after modulating the visual stimulation corresponding to each stimulation block, the method further includes:

[0084] Step S4: presenting each of the stimulus blocks as a corresponding visual stimulus, so that the subject generates an electroencephalogram response signal corresponding to the target stimulus block based on the target stimulus block.

[0085] Specifically, based on the coded stimulus combination and according to the stimulation paradigm, the stimulus blocks corresponding to each coded stimulus combination are respectively controlled to present corresponding visual stimuli so that the subject can focus on the target stimulus block and generate the electroencephalogram response signal corresponding to the target stimulus block.

[0086] In order to verify the performance of the SSVEP-based brain-computer interface stimulation modulation method provided in this application in the target stimulus recognition problem and the comfort of the modulated visual stimulation, the following experiments were conducted:

[0087] The subjects were 60 cm away from the stimulation display device. The EEG response signal acquisition device was a NeuroscanSynAmps2 64-256-conductor EEG amplifier, which was used to collect EEG data from the parietal and occipital regions of the subjects. The sampling rate was 1000 Hz. The reference electrode was located in the central region, and the ground electrode was located in the frontal region. The impedance of each electrode was less than 10 kΩ. The coding sequences used in this experiment included: '1010', '0101', '1001', '0110', '1100' and '0011'; the stimulation frequencies included: 10.0 Hz, 10.8 Hz, 11.6 Hz, 12.4 Hz, 13.2 Hz and 14.0 Hz. The above coding sequences and the above stimulation frequencies formed a total of 36 coding stimulation combinations, such as Figure 5 As shown, the 36 encoding stimulus combinations correspond one-to-one to the 36 stimulus blocks.

[0088] A total of 5 groups of experimental data were collected in this experiment, each of which included a target prompting stage and a target fixation stage. In the target prompting stage (lasting for 1 second), the display screen displayed a target position prompt point, and the subject moved his or her fixation angle to the target position prompt point during the target prompting stage; after the target prompting stage ended, the target fixation stage (lasting for 4 seconds) automatically started, and 36 stimulus blocks were simultaneously displayed on the display screen, each of which presented its corresponding visual stimulus. During the target fixation stage, the subject fixed his or her gaze on the target stimulus block corresponding to the target position prompt point, and the acquisition device was used to collect the EEG response signals generated by the subject's fixation on the visual stimulus presented by the target stimulus block; after the target fixation stage ended, the subject rested for 5 minutes, and after the rest, the next group of experiments was started.

[0089] In this experiment, the presentation time of the stimulus block corresponding to each coding stimulus combination was 3s, repeated 6 times, and the total presentation time was 18s. The measurement scale and EEG response signal data of 8 subjects were collected, and the comfort and decoding performance of different stimulation paradigms were discussed through offline analysis. The comfort and induced visual fatigue of the two visual stimulation paradigms were evaluated by comparative analysis of subjective comfort and visual fatigue scales, and the performance of the stimulation paradigm was evaluated based on the EEG response signal data.

[0090] After collecting the EEG response signal of the subject, the EEG response signal is preprocessed; the preprocessing includes: downsampling the EEG response signal from 1000 Hz to 250 Hz; processing the downsampled EEG response signal with a 50 Hz notch filter to eliminate power line interference, and removing the baseline of the EEG response signal to eliminate signal fluctuations; filtering the EEG response signal after the above processing with a 0.1 Hz to 90 Hz digital bandpass filter; and classifying the preprocessed EEG response signal data using a task-related component analysis algorithm, including:

[0091] Assume that the EEG response signal of the lth trial is Where N c Indicates the number of channels, N s Indicates the number of sampling points, N t represents the number of trials for each visual stimulus, then the linear combination of the lth trial is as follows:

[0092] Y l =w T X l

[0093] In the above formula, Represents the spatial filter, which is the optimization target of the correlation task analysis algorithm.

[0094] The optimal spatial filter is obtained by maximizing the covariance of all possible trial combinations. The covariance of each trial combination is calculated as follows:

[0095]

[0096] In the above formula, Indicates the first 1 The signal of the ith channel in the trial; Indicates the first 2 The signal of the jth channel in the trial; S represents the covariance matrix between different trials.

[0097] by Represents the connection matrix of all trials, and transforms the signal Y lThe variance of is normalized to 1, as shown below:

[0098]

[0099] In the above formula, j 1 and j 2 represents the index of the channel corresponding to the EEG response signal; Q represents the covariance matrix of the normalized constraints between different experiments; the above constrained optimization problem is expressed as follows through the Rayleigh-Ritz method:

[0100]

[0101] From the above, we can see that the spatial filter can be -1 The eigenvector corresponding to the maximum eigenvalue of the S matrix is ​​obtained.

[0102] The EEG response signal data is divided into training data and test data; the EEG response signals in the training data are averaged to obtain an individual template. And, by giving the optimal spatial filter, the correlation coefficient between the EEG response signal and the individual template of the nth visual stimulus is calculated as follows:

[0103]

[0104] In the above formula, ρ represents the correlation coefficient; X represents the EEG response signal in the test data; w n represents the nth spatial filter.

[0105] Using filter bank analysis, the signal is decomposed into sub-band components in order to effectively extract harmonics. The recognition formula for the target visual stimulus is as follows:

[0106]

[0107] In the above formula, N k Represents the total number of target visual stimuli; N m represents the number of subbands; a(m) represents the weight function.

[0108] In this experiment, EEG response signal data of ten subjects were collected. Based on the EEG response signal data of ten subjects, EEG response signals formed by visual stimulation modulated by the brain-computer interface stimulation modulation method provided in this application were obtained. The average classification accuracy in 4s was 81.7±12.6%; and

[0109] In this experiment, the same stimulation frequency and stimulation layout were used to conduct user experience evaluation on the stimulation paradigm and the standard stimulation paradigm provided in this application. The evaluation results are as follows:

[0110] like Figure 6As shown, compared with the standard stimulation paradigm with fixed brightness amplitude depth, the stimulation paradigm provided by the present application significantly improved the user's comfort (p<0.01); and significantly reduced the flicker perception (p<0.05).

[0111] The above-mentioned embodiment provides a brain-computer interface stimulation modulation method based on SSVEP, which obtains a preset stimulation paradigm, a coding sequence set and a stimulation frequency set, determines the number of stimulation blocks based on the number of coding sequences and the number of stimulation frequencies, and modulates the visual stimulation with a sine wave variation in brightness amplitude depth corresponding to the stimulation block according to the stimulation paradigm based on the coding sequence and the stimulation frequency. The method not only expands the display form of the stimulation block, but also improves the comfort of the user when looking at the visual stimulation presented by the stimulation block, thereby reducing the user's visual and mental fatigue.

[0112] like Figure 7 As shown, in this embodiment, the present invention provides a brain-computer interface stimulation modulation system based on SSVEP, comprising:

[0113] The stimulation block generation module 201 is used to obtain a preset coding sequence set, a stimulation frequency set and a stimulation paradigm; the coding sequence set includes a plurality of coding sequences; the coding sequence includes a plurality of code elements, and the code elements correspond to the brightness amplitude depth coefficients; the stimulation frequency set includes a plurality of stimulation frequencies; the stimulation paradigm is used to modulate the brightness amplitude depth and flicker frequency of the visual stimulation based on the coding sequence and the stimulation frequency; wherein the brightness amplitude depth of the visual stimulation changes sinusoidally over time;

[0114] A coding stimulus combination generating module 202 is used to generate a coding stimulus combination of the coding sequence and the stimulus frequency based on the coding sequence and the stimulus frequency; a single coding stimulus combination is a combination of a single coding sequence and a single stimulus frequency;

[0115] The stimulus modulation module 203 is used to modulate the visual stimulus corresponding to each stimulus block based on the coded stimulus combination and using the stimulus paradigm.

[0116] See also Figure 8 , showing a schematic structural diagram of a computer device provided by the present invention in one embodiment;

[0117] like Figure 8As shown, in this embodiment, the computer device 300 provided by the present invention includes a memory 301 and a processor 302, the memory 301 is used to store computer programs; the processor 302 is used to execute the computer program stored in the memory 301, so that the computer device 300 executes the SSVEP-based brain-computer interface stimulation modulation method of any of the above embodiments of the present application. Since the specific implementation process of the steps of the SSVEP-based brain-computer interface stimulation modulation method has been described in detail in the above embodiments, it will not be repeated here.

[0118] The memory 301 includes: ROM (Read Only Memory image), RAM (Random Access Memory), a disk, a USB flash drive, a memory card, or an optical disk, etc., which can store program codes.

[0119] The processor 302 is connected to the memory 301 and is used to execute the computer program stored in the memory 301 so that the computer device 300 executes the above-mentioned SSVEP-based brain-computer interface stimulation modulation method.

[0120] The present application embodiment also provides a computer-readable storage medium. A person of ordinary skill in the art can understand that all or part of the steps in the method for implementing the above embodiment can be completed by a program to instruct the processor, and the program can be stored in a computer-readable storage medium, and the storage medium is a non-transitory medium, such as a random access memory, a read-only memory, a flash memory, a hard disk, a solid-state hard disk, a magnetic tape, a floppy disk, an optical disc, and any combination thereof. The above storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or a data center that includes one or more available media integrated. The available medium can be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a digital video disc (DVD)), or a semiconductor medium (e.g., a solid-state hard disk (SSD)), etc.

[0121] The present application embodiment may also provide a computer program product, the computer program product including one or more computer instructions. When the computer instructions are loaded and executed on a computing device, the process or function described in the embodiment of the present application is generated in whole or in part. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions may be transmitted from a website site, computer or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer or data center.

[0122] When the computer program product is executed by a computer, the computer executes the method described in the above method embodiment. The computer program product may be a software installation package, and when the above method is required, the computer program product may be downloaded and executed on a computer.

[0123] The descriptions of the processes or structures corresponding to the above-mentioned figures have different emphases. For parts that are not described in detail in a certain process or structure, please refer to the relevant descriptions of other processes or structures.

[0124] The above embodiments are merely illustrative of the principles and effects of the present application and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present application shall still be covered by the claims of the present application.

Claims

1. A brain-computer interface stimulation modulation method based on SSVEP, characterized in that: The method comprises: Acquire a preset coding sequence set, a stimulation frequency set and a stimulation paradigm; the coding sequence set includes a plurality of coding sequences; the coding sequence includes a plurality of code elements, and the code elements correspond to brightness amplitude depth coefficients; the stimulation frequency set includes a plurality of stimulation frequencies; the stimulation paradigm is used to modulate the brightness amplitude depth and flicker frequency of visual stimulation based on the coding sequence and the stimulation frequency; wherein the brightness amplitude depth of the visual stimulation changes sinusoidally over time; Based on the coding sequence and the stimulation frequency, generating a coding stimulation combination of the coding sequence and the stimulation frequency; a single coding stimulation combination is a combination of a single coding sequence and a single stimulation frequency; Based on the coded stimulus combination, the visual stimulus corresponding to each stimulus block is modulated using the stimulus paradigm.

2. The method according to claim 1, characterized in that The stimulation paradigm is constructed in a manner including: Amplitude keying is adopted to control the amplitude of the sine wave using the brightness amplitude depth, and the stimulation frequency is taken as the number of cycles of the sine wave per unit time to construct the stimulation paradigm so as to load the signal onto the sine wave.

3. The method according to claim 1, characterized in that The step of generating a coding stimulation combination of the coding sequence and the stimulation frequency based on the coding sequence and the stimulation frequency comprises: According to the coding sequence and the stimulation frequency, all possible coding stimulation combinations between the coding sequence and the stimulation frequency are generated.

4. The method according to claim 1, characterized in that: The step of modulating the visual stimulus corresponding to each stimulus block based on the coded stimulus combination and utilizing the stimulus paradigm comprises: Based on each of the coded stimulus combinations, the corresponding stimulus blocks are generated respectively; based on the coded stimulus combinations, the visual stimulus corresponding to each of the stimulus blocks is modulated according to the stimulus paradigm.

5. The method according to claim 1, characterized in that When the coding sequence is encoded using a binary coding method and the total number of code elements in the coding sequence is an even number, the number of code elements of the two types of code elements in the coding sequence is equal.

6. The method according to claim 1, characterized in that The stimulation blocks with the same stimulation frequency and / or the same coding sequence are arranged in a non-adjacent manner.

7. The method according to claim 1, characterized in that After modulating the visual stimulus corresponding to each of the stimulus blocks, the method further includes: Each of the stimulation blocks is presented as a corresponding visual stimulus, so that the subject generates an electroencephalographic response signal corresponding to the target stimulation block based on the target stimulation block.

8. A brain-computer interface stimulation modulation system based on SSVEP, characterized in that: include: An acquisition module, used to acquire a preset coding sequence set, a stimulation frequency set and a stimulation paradigm; the coding sequence set includes a plurality of coding sequences; the coding sequence includes a plurality of code elements, and the code elements correspond to brightness amplitude depth coefficients; The stimulation frequency set includes several stimulation frequencies; the stimulation paradigm is used to modulate the brightness, amplitude, depth and flicker frequency of the visual stimulation based on the coding sequence and the stimulation frequency; wherein the brightness, amplitude, depth of the visual stimulation changes sinusoidally over time; A coding stimulation combination generating module, used for generating a coding stimulation combination of the coding sequence and the stimulation frequency based on the coding sequence and the stimulation frequency; a single coding stimulation combination is a combination of a single coding sequence and a single stimulation frequency; The stimulus modulation module is used to modulate the visual stimulus corresponding to each stimulus block based on the coded stimulus combination and using the stimulus paradigm.

9. A computer device, characterized in that: The device comprises: Memory for storing computer programs; A processor, configured to execute the computer program stored in the memory so as to enable the apparatus to perform the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed, the method according to any one of claims 1 to 7 is implemented.

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