Hybrid brain-computer target augmentation method based on single high-frequency steady-state and transient features

Abstract

The application relates to a single high-frequency steady-state and transient feature-based hybrid brain-computer target amplification method, and belongs to the technical field of brain-computer interface coding, and solves the problem that the low practicability of a BCI is caused by the few coded brain-computer interface instructions in the prior art. The amplification method comprises the following steps: determining the number of sub-spellers, the number of stimulation blocks included in each sub-speller, and the initial stimulation time point corresponding to each stimulation block in each sub-speller; determining the display phase corresponding to each sub-speller according to the phase interval range and the number of sub-spellers, and determining the brightness of the display image of each stimulation block in each sub-speller according to the display phase corresponding to each sub-speller, a preset background frequency and a stimulation screen refresh rate; and starting to display the image of each stimulation block in each sub-speller to a subject at the corresponding initial stimulation time point according to the brightness and the stimulation screen refresh rate. The amplification of the brain-computer interface instruction is realized, and the practicability and applicability of the BCI system are improved.

Description

Technical Field

[0001] This invention relates to the field of brain-computer interface coding technology, and in particular to a hybrid brain-computer target amplification method based on a single high-frequency steady-state and transient feature. Background Technology

[0002] Brain-computer interface (BCI) is a system that directly translates the activities of the central nervous system into artificial outputs. It can replace, repair, enhance, supplement or improve the normal outputs of the central nervous system, thereby improving the interaction between the central nervous system and the internal and external environment.

[0003] Current brain-computer interfaces typically use two encoding methods, Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA), to encode instructions.

[0004] Time Division Multiple Access (TDMA) encodes instructions at different points in time and presents them in a time-division manner, thus enabling an unlimited number of instruction encodings and typically inducing transient EEG features. However, as the number of instructions increases, the shared time-domain channel characteristic of TDMA leads to a significant increase in the time required to complete the encoding of all instructions, thereby affecting the overall performance of the brain-computer interface.

[0005] Frequency division multiple access (FDMA) encodes commands by using different stimulation frequencies and phases, which usually induces steady-state EEG characteristics. Currently, stimulation at frequencies greater than 30 Hz has the advantages of weak stimulation and high comfort, attracting widespread attention. However, it also has problems such as a narrow usable frequency band, low frequency resolution, and weak separability, which limits the number of brain-computer interface commands.

[0006] Therefore, there is an urgent need for an encoding technology scheme to amplify brain-computer interface commands. Summary of the Invention

[0007] Based on the above analysis, the embodiments of the present invention aim to provide a hybrid brain-computer interface target amplification method based on a single high-frequency steady-state and transient features, in order to solve the problem of low practicality of BCI caused by the limited number of encoded brain-computer interface instructions in the prior art.

[0008] This invention provides a hybrid brain-computer interface target amplification method based on a single high-frequency steady-state and transient feature, the amplification method comprising:

[0009] The number of sub-spelling units and the number of stimulation blocks included in each sub-spelling unit are determined based on the preset total number of brain-computer stimulation blocks. The initial stimulation time point corresponding to each stimulation block in each sub-spelling unit is determined according to the preset stimulation time and the number of stimulation blocks included in each sub-spelling unit.

[0010] The display phase corresponding to each sub-spelling device is determined based on the phase interval range and the number of sub-spelling devices. The brightness of the image displayed by each stimulus block in each sub-spelling device is determined based on the display phase corresponding to each sub-spelling device, the preset background frequency, and the stimulation screen refresh rate.

[0011] The image of each stimulus block in each sub-spelling device is displayed to the subject at the corresponding stimulus screen refresh rate, starting from the initial stimulus time point according to the brightness described above.

[0012] Based on a further improvement to the above amplification method, the determination of the number of sub-spelling units and the number of stimulation blocks included in each sub-spelling unit based on a preset total number of brain-computer stimulation blocks includes:

[0013] Brain-computer interface stimulation blocks are evenly distributed to each sub-spelling device, so that each sub-spelling device includes the same number of stimulation blocks.

[0014] Based on a further improvement to the above amplification method, the step of determining the initial stimulation time point corresponding to each stimulation block in each sub-spelling device according to the preset stimulation time and the number of stimulation blocks included in each sub-spelling device includes:

[0015] The preset stimulation time is divided into multiple time periods according to the number of stimulation blocks included in each sub-spelling device. The starting time point of each time period is assigned to the stimulation blocks in sequence according to the sequence number of the stimulation blocks, which serves as the initial stimulation time point of each stimulation block, so that the time interval between the initial stimulation time points of two stimulation blocks with adjacent sequence numbers in the same sub-spelling device is the same.

[0016] Among them, the stimulus blocks with the same sequence number included in different sub-spellings correspond to the same initial stimulus time point.

[0017] Based on a further improvement to the above amplification method, the step of determining the initial stimulation time point corresponding to each stimulation block in each sub-spelling device according to the preset stimulation time and the number of stimulation blocks included in each sub-spelling device includes:

[0018] The preset stimulation time is divided into multiple time periods on an even basis according to the number of stimulation blocks included in each sub-spelling device. The start time of each time period is randomly assigned to each stimulation block as the initial stimulation time point of each stimulation block.

[0019] Among them, the stimulus blocks with the same sequence number included in different sub-spellings correspond to the same initial stimulus time point.

[0020] Based on a further improvement to the above amplification method, the step of determining the display phase corresponding to each sub-spelling device according to the phase interval range and the number of sub-spelling devices includes:

[0021] The phase interval is divided equally according to the number of sub-spellings, so that the phase interval of the display phase corresponding to the stimulus blocks included in two adjacent sub-spellings is the same.

[0022] In this context, the presentation phase of each stimulus block in the same sub-speller is the same.

[0023] Based on further improvements to the above amplification method, the preset background frequency is less than or equal to half of the stimulation screen refresh rate, and greater than or equal to 30Hz.

[0024] Based on a further improvement to the above amplification method, the step of determining the brightness of the displayed image of each stimulus block in each sub-spelling device according to the display phase corresponding to each sub-spelling device, the preset background frequency, and the stimulation screen refresh rate includes:

[0025] The number of images displayed in each display cycle is determined based on a preset background frequency and a stimulation screen refresh rate; the display cycle is the reciprocal of the preset background frequency.

[0026] The brightness of each image displayed in each display cycle is determined based on the display phase corresponding to each sub-speller, wherein the brightness of each image in a display cycle varies according to a sine function.

[0027] Based on further improvements to the amplification method described above, the brightness of the image displayed for each stimulus block is determined using the following formula:

[0028]

[0029] Where s(f,i) represents the stimulus brightness of the i-th image in one display cycle for each stimulus block, f represents the preset background frequency, and Refresh Rate represents the stimulus screen refresh rate. This indicates the presentation phase of the nth sub-speller.

[0030] Based on the further improvement of the above amplification method, the time interval between two adjacent images displayed in each stimulus block is the same, and the display time of each image is less than the refresh cycle of the stimulus block.

[0031] Based on further improvements to the above amplification method, the image content of images with different brightness levels included in the same display cycle is different.

[0032] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0033] 1. The number of sub-spelling units and the number of stimulation units included in each sub-spelling unit are determined by the total number of brain-computer stimulation blocks. Different initial stimulation time points are set for each stimulation block in the same sub-spelling unit, and different display phases are set for each sub-spelling unit. This ensures that each stimulation block has a unique display phase and initial stimulation time point, which increases the number of instruction codes for stimulation blocks, expands the brain-computer target, and improves the practicality and applicability of the BCI system.

[0034] 2. By setting the same initial stimulation time point for multiple stimulation blocks within the same sub-spelling unit, and setting the same display phase for different sub-spelling units, and adjusting the image brightness according to the display phase, the distinguishability of different stimulation blocks is improved, thereby enhancing the accuracy of brain-computer target recognition.

[0035] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0036] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0037] Figure 1 A flowchart illustrating the hybrid brain-computer interface target amplification method based on a single high-frequency steady-state and transient feature provided in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the distribution of stimulation blocks provided in an embodiment of the present invention. Detailed Implementation

[0039] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0040] To address the limitation on the limited number of encodeable instructions resulting from time-division multiple access (TDMA) and frequency-division multiple access (FDMA) encoding of brain-computer interfaces (BCI) systems in existing technologies, a specific embodiment of this invention discloses a hybrid brain-computer interface target amplification method based on a single high-frequency steady-state and transient feature. Figure 1 As shown, the amplification method includes:

[0041] Step S1: Determine the number of sub-spelling units and the number of stimulation blocks included in each sub-spelling unit based on the preset total number of brain-computer stimulation blocks. Determine the initial stimulation time point corresponding to each stimulation block in each sub-spelling unit according to the preset stimulation time and the number of stimulation blocks included in each sub-spelling unit.

[0042] Step S2: Determine the display phase corresponding to each sub-spelling device based on the phase interval range and the number of sub-spelling devices. Determine the brightness of the image displayed by each stimulus block in each sub-spelling device based on the display phase corresponding to each sub-spelling device, the preset background frequency, and the stimulation screen refresh rate.

[0043] Step S3: Display the image of each stimulus block in each sub-spelling device to the subject at the corresponding stimulus screen refresh rate, according to the brightness described above, starting at the corresponding stimulus initial time point.

[0044] Specifically, such as Figure 1 As shown, in step S1, the total number of brain-computer stimulation blocks is the total number of brain-computer target instructions that need to be encoded, and each brain-computer target instruction corresponds to one stimulation block. It is worth noting that the method provided by the embodiments of the present invention can provide encoding for an unlimited number of brain-computer target instructions, and can realize the display of an unlimited number of stimulation blocks. After receiving the display of any stimulation block, the subject can know the stimulation block observed by receiving and analyzing the subject's brain waves.

[0045] Preferably, determining the number of sub-spelling units and the number of stimulation blocks included in each sub-spelling unit based on a preset total number of brain-computer stimulation blocks includes:

[0046] Brain-computer interface stimulation blocks are evenly distributed to each sub-spelling device, so that each sub-spelling device includes the same number of stimulation blocks.

[0047] Specifically, the number of sub-spelling devices and the number of stimulation blocks included in each sub-spelling device are determined based on the total number of brain-computer stimulation blocks. For example, if the total number of brain-computer stimulation blocks is 12, it can be determined as 2 sub-spelling devices with 6 stimulation blocks in each sub-spelling device, or as 3 sub-spelling devices with 4 stimulation blocks in each sub-spelling device.

[0048] Preferably, the number of sub-spelling devices ranges from 1 to 100, and each sub-spelling device includes 1 to 20 stimulation blocks. That is, the brain-computer interface (BCI) target amplification method based on a single high-frequency steady-state and transient feature provided by this invention can amplify brain-computer instructions up to 2000, enabling the BCI system to achieve richer brain-computer instruction encoding within a limited frequency band. This breaks through the limitations of traditional encoding methods, enhances the practicality and applicability of the BCI system, and is of great significance, especially in the development of weak stimulation comfort brain-computer interface systems. It can achieve more precise instruction control without increasing the stimulation intensity, ensuring the comfort and safety of the user experience.

[0049] Specifically, the preset stimulation time is determined based on the time when the subject receives the stimulus, generally 1.5 seconds. For each stimulus block included in the same sub-spelling device, time-division multiple access is used to determine the initial stimulation time point for each stimulus block, so that each stimulus block in the same sub-spelling device corresponds to a different initial stimulation time point.

[0050] Preferably, determining the initial stimulation time point corresponding to each stimulation block in each sub-spelling device based on the preset stimulation time and the number of stimulation blocks included in each sub-spelling device includes:

[0051] The preset stimulation time is divided into multiple time periods according to the number of stimulation blocks included in each sub-spelling device. The starting time point of each time period is assigned to the stimulation blocks in sequence according to the sequence number of the stimulation blocks, which serves as the initial stimulation time point of each stimulation block, so that the time interval between the initial stimulation time points of two stimulation blocks with adjacent sequence numbers in the same sub-spelling device is the same.

[0052] Among them, the stimulus blocks with the same sequence number included in different sub-spellings correspond to the same initial stimulus time point.

[0053] Specifically, within each sub-spelling device, the preset stimulation time is divided equally according to the number of stimulation blocks included in that sub-spelling device. After the division, the stimulation blocks included in that sub-spelling device correspond to different initial stimulation time points, and the time interval between the initial stimulation time points of two adjacent stimulation blocks within the same sub-spelling device is the same.

[0054] For example, the sub-spelling device includes 4 stimulus blocks with a stimulation time of 1 second. After being divided into 4 parts, the initial stimulation time points are 0, 0.25s, 0.5s, and 0.75s, respectively. At the same time, 0, 0.25s, 0.5s, and 0.75s are assigned according to the sequence number of the stimulus blocks, that is, the first stimulus block corresponds to the initial stimulation time point of 0, the second stimulus block corresponds to the initial stimulation time point of 0.25s, the third stimulus block corresponds to the initial stimulation time point of 0.5s, and the fourth stimulus block corresponds to the initial stimulation time point of 0.75s.

[0055] Preferably, determining the initial stimulation time point corresponding to each stimulation block in each sub-spelling device based on the preset stimulation time and the number of stimulation blocks included in each sub-spelling device includes:

[0056] The preset stimulation time is divided into multiple time periods on an even basis according to the number of stimulation blocks included in each sub-spelling device. The start time of each time period is randomly assigned to each stimulation block as the initial stimulation time point of each stimulation block.

[0057] Among them, the stimulus blocks with the same sequence number included in different sub-spellings correspond to the same initial stimulus time point.

[0058] Specifically, the initial stimulus time points are randomly assigned as follows: 0.25s for the first stimulus block, 0s for the second, 0.5s for the third, and 0.75s for the fourth. Furthermore, stimulus blocks with the same sequence number in different sub-spellings have the same initial stimulus time point; that is, there exists a sub-spelling where the initial stimulus time point for the first stimulus block is 0.25s, the initial stimulus time point for the second is 0s, the initial stimulus time point for the third is 0.5s, and the initial stimulus time point for the fourth is 0.75s.

[0059] Specifically, such as Figure 1 As shown, in step S2, the phase interval range is generally set to 2π. If the number of sub-spellers is 3, the 2π phase is divided into 3 display phases, so that each sub-speller corresponds to a unique display phase. Then, each stimulus block included in the sub-speller corresponds to the display phase.

[0060] Preferably, determining the display phase corresponding to each sub-spelling device based on the phase interval range and the number of sub-spelling devices includes:

[0061] The phase interval is divided equally according to the number of sub-spellings, so that the phase interval of the display phase corresponding to the stimulus blocks included in two adjacent sub-spellings is the same.

[0062] In this context, the presentation phase of each stimulus block in the same sub-speller is the same.

[0063] Specifically, the phase interval range of 2π is divided into 3 display phases, which are 0, 2π / 3 and 4π / 3 after averaging. That is, the display phase of the first sub-spelling device is 0, the display phase of the second sub-spelling device is 2π / 3 and the display phase of the third sub-spelling device is 4π / 3.

[0064] It is worth noting that the presentation phases of the stimulus blocks within the same sub-spelling unit are the same. That is, the presentation phase of the stimulus blocks in the first sub-spelling unit is 0, the presentation phase of the stimulus blocks in the second sub-spelling unit is 2π / 3, and the presentation phase of the stimulus blocks in the third sub-spelling unit is 4π / 3.

[0065] Specifically, after determining the initial stimulation time point and corresponding presentation phase of the brain-computer stimulation block, each brain-computer stimulation block is encoded.

[0066] Specifically, the stimulation screen refresh rate is the screen refresh rate observed by the subject, such as 240Hz, meaning the stimulation screen can display 240 images per second; the background frequency needs to be set in advance, which is the single high frequency in this invention.

[0067] Specifically, such as Figure 2 As shown, a stimulus block comprises n sub-spellers, and each sub-speller comprises m stimulus blocks. That is, the presentation phases of the m stimulus blocks in each row are the same, and the initial stimulation time points of stimulus blocks with the same index in each column are the same.

[0068] Preferably, the preset background frequency is less than or equal to half of the screen refresh rate and greater than or equal to 30Hz.

[0069] Specifically, by displaying images at a background frequency, the subject generates brainwave signals of the same frequency. In this invention, each stimulation block causes the subject to generate brainwave signals at the background frequency. Generally, for a stimulation screen refresh rate of 240Hz, the background frequency can be selected as 60Hz, 40Hz, or 48Hz.

[0070] Specifically, in step S2, the brightness of the image displayed by each stimulus block in each sub-spelling device is determined based on the display phase corresponding to each sub-spelling device, the preset background frequency, and the refresh rate of the stimulation screen.

[0071] Preferably, determining the brightness of the image displayed in each stimulus block in each sub-spelling device based on the display phase corresponding to each sub-spelling device, the preset background frequency, and the stimulation screen refresh rate includes:

[0072] The number of images displayed in each display cycle is determined based on a preset background frequency and a stimulation screen refresh rate; the display cycle is the reciprocal of the preset background frequency.

[0073] The brightness of each image displayed in each display cycle is determined based on the display phase corresponding to each sub-speller, wherein the brightness of each image in a display cycle varies according to a sine function.

[0074] Specifically, the background frequency is set in advance, and the refresh rate of the stimulation screen is a fixed parameter. The number of images in each display cycle is determined according to the background frequency and the refresh rate of the stimulation screen. When the refresh rate of the stimulation screen is 240Hz and the background frequency is 60Hz, each display cycle includes 4 images. The duration of each display cycle is 1 / 60s. Within one display cycle, 4 images with different brightness are displayed sequentially. The 4 images with different brightness are displayed to the subject according to the refresh rate of the stimulation screen.

[0075] Once the stimulus block reaches its initial stimulation time, the display begins. During the display, the images are shown repeatedly according to a display cycle. That is, four images with different brightness levels are shown sequentially in one display cycle, and the same four images with different brightness levels are shown in the next display cycle until the set time is reached. During this period, each image is shown to the subject according to the refresh rate of the stimulation screen.

[0076] Specifically, the brightness of the four images included within each sub-spelling unit varies. Furthermore, the brightness of the four images changes according to a sine function within the same display cycle.

[0077] Preferably, the brightness of the image used to display each stimulus block is determined by the following formula:

[0078]

[0079] Where s(f, i) represents the stimulus brightness of the i-th image in one display cycle for each stimulus block, f represents the preset background frequency, and Refresh Rate represents the stimulus screen refresh rate. This indicates the presentation phase of the nth sub-speller.

[0080] Specifically, for each stimulus block, the brightness of the image used for display is displayed cyclically according to the background frequency. If there are 4 images in a display cycle, the brightness is calculated according to the above formula.

[0081] It is worth noting that the display phases of the different sub-spelling machines are different, meaning that the brightness of the four images displayed by the different sub-spelling machines will be slightly different, thus providing different stimuli to the subjects.

[0082] Preferably, the image content of the images with different brightness levels included in the same display cycle is different.

[0083] Specifically, for images used to be displayed within the same period, in addition to differences in brightness, different image content is provided for images of different brightness in order to increase the stimulation to the subjects and improve the stimulation effect on the subjects.

[0084] For example, different numbers or letters can be added to an image as image content, thereby increasing the distinction between images and increasing the stimulation effect.

[0085] Preferably, the time interval between two adjacent images displayed in each stimulus block is the same, and the display time of each image is less than the refresh cycle of the stimulus block.

[0086] Specifically, the time interval between two adjacent images displayed by each stimulus block is determined according to the refresh rate of the stimulus screen. When the refresh rate of the stimulus screen is 240Hz, the time interval is 1 / 240s, that is, the refresh cycle of the stimulus block is 1 / 240s.

[0087] Compared with existing technologies, the hybrid brain-computer interface (BCI) target amplification method based on single high-frequency steady-state and transient features provided in this invention determines the number of sub-spelling units and the number of stimulation units included in each sub-spelling unit by determining the total number of brain-computer stimulation blocks. Different initial stimulation time points are set for each stimulation block within the same sub-spelling unit, and different display phases are set for each sub-spelling unit, ensuring that each stimulation block has a unique display phase and initial stimulation time point. This increases the number of instruction codes for stimulation blocks, achieves brain-computer target amplification, and improves the practicality and applicability of the BCI system. Furthermore, by setting the same initial stimulation time points for multiple stimulation blocks within the same sub-spelling unit and setting display phases with the same phase intervals for different sub-spelling units, and adjusting the image brightness according to the display phase, the distinguishability of different stimulation blocks is improved, thus enhancing the accuracy of brain-computer target recognition.

[0088] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0089] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for brain-computer interface target amplification based on a hybrid of single high-frequency steady-state and transient features, characterized in that, The amplification method includes: The number of sub-spelling units and the number of stimulation blocks included in each sub-spelling unit are determined based on the preset total number of brain-computer stimulation blocks. The initial stimulation time point corresponding to each stimulation block in each sub-spelling unit is determined according to the preset stimulation time and the number of stimulation blocks included in each sub-spelling unit. The display phase corresponding to each sub-spelling device is determined based on the phase interval range and the number of sub-spelling devices. The brightness of the image displayed by each stimulus block in each sub-spelling device is determined based on the display phase corresponding to each sub-spelling device, the preset background frequency, and the stimulation screen refresh rate. The image of each stimulus block in each sub-spelling device is displayed to the subject at the corresponding stimulus screen refresh rate, starting from the initial stimulus time point according to the brightness described above.

2. The amplification method according to claim 1, characterized in that, The determination of the number of sub-spelling units and the number of stimulation blocks included in each sub-spelling unit based on the preset total number of brain-computer stimulation blocks includes: Brain-computer interface stimulation blocks are evenly distributed to each sub-spelling device, so that each sub-spelling device includes the same number of stimulation blocks.

3. The amplification method according to claim 2, characterized in that, The step of determining the initial stimulation time point corresponding to each stimulation block in each sub-spelling device based on the preset stimulation time and the number of stimulation blocks included in each sub-spelling device includes: The preset stimulation time is divided into multiple time periods according to the number of stimulation blocks included in each sub-spelling device. The starting time point of each time period is assigned to the stimulation blocks in sequence according to the sequence number of the stimulation blocks, which serves as the initial stimulation time point of each stimulation block, so that the time interval between the initial stimulation time points of two stimulation blocks with adjacent sequence numbers in the same sub-spelling device is the same. Among them, the stimulus blocks with the same sequence number included in different sub-spellings correspond to the same initial stimulus time point.

4. The amplification method according to claim 2, characterized in that, The step of determining the initial stimulation time point corresponding to each stimulation block in each sub-spelling device based on the preset stimulation time and the number of stimulation blocks included in each sub-spelling device includes: The preset stimulation time is divided into multiple time periods on an even basis according to the number of stimulation blocks included in each sub-spelling device. The start time of each time period is randomly assigned to each stimulation block as the initial stimulation time point of each stimulation block. Among them, the stimulus blocks with the same sequence number included in different sub-spellings correspond to the same initial stimulus time point.

5. The amplification method according to claim 1, characterized in that, The step of determining the display phase corresponding to each sub-spelling device based on the phase interval range and the number of sub-spelling devices includes: The phase interval is divided equally according to the number of sub-spellings, so that the phase interval of the display phase corresponding to the stimulus blocks included in two adjacent sub-spellings is the same. In this context, the presentation phase of each stimulus block in the same sub-speller is the same.

6. The amplification method according to claim 1, characterized in that, The preset background frequency is less than or equal to half of the screen refresh rate and greater than or equal to 30Hz.

7. The amplification method according to claim 6, characterized in that, The step of determining the brightness of the image displayed in each stimulus block in each sub-spelling device based on the display phase corresponding to each sub-spelling device, the preset background frequency, and the stimulation screen refresh rate includes: The number of images displayed in each display cycle is determined based on a preset background frequency and a stimulation screen refresh rate; the display cycle is the reciprocal of the preset background frequency. The brightness of each image displayed in each display cycle is determined based on the display phase corresponding to each sub-speller, wherein the brightness of each image in a display cycle varies according to a sine function.

8. The amplification method according to claim 7, characterized in that, The brightness of the image used to display each stimulus block is determined by the following formula: Where s(f, i) represents the stimulus brightness of the i-th image in one display cycle for each stimulus block, f represents the preset background frequency, and Refresh Rate represents the stimulus screen refresh rate. This indicates the presentation phase of the nth sub-speller.

9. The amplification method according to claim 8, characterized in that, The time interval between two adjacent images displayed in each stimulus block is the same, and the display time of each image is less than the refresh cycle of the stimulus block.

10. The amplification method according to claim 7, characterized in that, The image content of images with different brightness levels included within the same display period is different.

Images