Brain Stimulator

Abstract

To stimulate a brain with a signal according to the phase shift of a brain wave observed.SOLUTION: A brain stimulating device (1) includes: feature extraction means (C2) for extracting a feature of a brain wave pattern (21), on the basis of the brain wave pattern (21) being a time history of brain waves measured by an electro-encephalograph (11+C1); waveform generating means (C3) for generating a waveform (16) to stimulate a brain on the basis of the feature of the brain wave pattern (21), the waveform generating means (C3) generating the waveform (16) for stimulating a brain wave that is phase-shifted with respect to a phase of the waveform of the brain wave pattern (21) on the basis of a phase shift between a phase of the brain wave at a generating source of the brain wave and a brain wave phase at a position measured by the electro-encephalograph (11+C1); and stimulation means (C4) for giving stimulation of the waveform generated by the waveform generating means (C3) to the brain of a subject (2).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a brain stimulation device that applies electrical stimulation to human brain activity, and in particular to a brain stimulation device that can be used to treat diseases related to brain activity, such as epilepsy, depression, speech disorders, schizophrenia, Parkinson's disease, rehabilitation of stroke patients, intractable pain, and sleep disorders. [Background technology]

[0002] In conventional brain science research, the techniques described in the following Patent Documents 1 to 3 and Non-Patent Document 1 are known as techniques for improving symptoms of diseases related to brain activity by electrical current stimulation. Patent Document 1 (JP 2018-68511 A) describes a technique for measuring the subject's brain waves through an electrode (26) of a stimulation device (2), generating a weak current from a second electrode (27) to activate the DMN (Default Mode Network) based on the result of the brain wave determination, and providing stimulation. In the technique described in Patent Document 1, the signal components of α waves, β waves, θ waves, and δ waves are identified from the frequency spectrum of the brain wave signal, and if the DMN is in an inactive state such that the phases of the α wave components are not in phase in multiple brain regions (multiple channels) or the amplitude of the α wave components is not above a threshold, stimulation is provided to the subject's head to activate the DMN. In addition, in the technology described in Patent Document 1, the stimuli applied include alternating currents (sine waves) that oscillate at the alpha band frequency and have the same phase as all areas, or alternating currents of the same frequency and phase as all areas, a weak current that is in phase with other DMN relevant areas is applied only to some brain areas with low DMN-related activity, a weak current is applied to areas that are not DMN relevant areas to reduce brain waves, and the timing of the application of stimuli is controlled according to the phase difference of the alpha wave component related to the DMN relevant area.

[0003] Patent Document 2 (JP Patent Publication No. 2020-500567) describes a technology for improving memory by applying spindle-like stimulation to the brain during sleep in response to the occurrence of slow oscillations contained in an electroencephalogram signal measured during sleep. In Patent Document 2, the frequency of the spindle component (230) of the spindle-like stimulation is set within the frequency range of the spindle component of the electroencephalogram or is set in phase with it.

[0004] Patent Document 3 (JP Patent Publication 62-155863 A) describes a technology in which a weak current in phase with the alpha wave component of detected brain waves is passed from an electrode (12) to synchronize and enhance the alpha waves in the brain waves, making it easier to concentrate, meditate, and enter a state of mental stability.

[0005] Non-Patent Document 1 describes a technology that applies electrical stimulation of the same frequency and phase in response to slow brain waves (low-frequency brain waves) measured during sleep in order to improve long-term memory. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-68511 A ("0019"-"0020", "0027", "0038"-"0041", "0065"-"0069", "0072", Figures 7, 8, 11, 13, and 15) [Patent Document 2] Special Publication No. 2020-500567 ("0036" - "0048") [Patent Document 3] JP 62-155863 A (Page 2, lower left column, line 19 - Page 3, upper right column, line 3) [Non-patent literature]

[0007] [Non-Patent Document 1] Nicholas Ketz, et al., "Closed-Loop Slow-Wave tACS Improves Sleep-Dependent Long-Term Memory Generalization by Modulating Endogenous Oscillations", The Journal of Neuroscience, August 15 2018, 38(33):7314-7326 Summary of the Invention [Problem to be solved by the invention]

[0008] In the above-mentioned conventional technology, when applying electric current stimulation to brain activity, an electric current in phase with the measured brainwave is applied without considering the intrinsic brainwave phase. In other words, due to the effect of volume conduction, a time lag occurs between the brainwave potential source inside the brain and the arrival of the brainwave at the detection position of the electroencephalograph installed on the outer surface of the head, resulting in a phase delay of the brainwave. Therefore, in the conventional method, the effect of electric current stimulation may be insufficient or may have an adverse effect when it is in the opposite phase to the endogenous EEG. This may be one of the reasons why the effect of electric current stimulation in human brain science research has not shown a consistent trend, and it is also one of the risk factors for using electric current stimulation in clinical applications.

[0009] The technical objective of the present invention is to stimulate the brain with a signal corresponding to the phase shift of the observed electroencephalogram. [Means for solving the problem]

[0010] In order to solve the above technical problem, the brain stimulation device of the invention described in claim 1 comprises: an electroencephalograph for measuring the subject's brain waves; A feature extraction means for extracting features of an electroencephalogram pattern based on an electroencephalogram pattern, which is a time history of electroencephalograms measured by the electroencephalograph; A waveform generating means for generating a waveform for stimulating the brain based on the features of the electroencephalogram pattern extracted by the feature extracting means.Step by step, a stimulation means for electrically stimulating the brain of the subject, the stimulation means applying a stimulus having a waveform generated by the waveform generating means; Equipped with 、 The waveform for stimulating the brain is Predefined according to the diagnosis subject The phase difference between the brainwaves at the source of the brainwaves and the brainwaves at the location measured by the electroencephalograph The deviation is calculated based on the distance between the source and the position measured by the electroencephalograph and on volume conduction. Based on the above, the phase of the electroencephalogram pattern is shifted from the phase of the waveform of the electroencephalogram pattern. It is a waveform, The waveform has a higher frequency than the frequency of the electroencephalogram pattern, and A waveform enveloped by an envelope wave corresponding to the frequency of the electroencephalogram pattern. child It is characterized by:

[0011] The invention described in claim 2 is the brain stimulation device described in claim 1, The characteristics of the brainwave pattern include the power ratio of the frequency of the brainwave pattern. The power ratio is calculated by dividing the power of a predetermined set frequency in the waveform of the electroencephalogram pattern by the power of all frequencies. Use It is characterized by: Effect of the Invention

[0013] According to the invention described in claim 1, compared to the conventional technology of applying a signal synchronized with the observed brain waves, it is possible to stimulate the brain with a signal corresponding to the phase shift of the observed brain waves, and to apply the desired stimulation to the source of the brain waves. According to the invention described in claim 1, a high-frequency waveform having an envelope wave can be used to apply a high-frequency stimulus corresponding to an electroencephalogram pattern. According to the invention recited in claim 2, the adverse effects of noise can be suppressed compared to a case in which the frequency power ratio is not used. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is an explanatory diagram of a brain stimulation device according to the present invention. [Diagram 2] FIG. 2 is an explanatory diagram of the control unit of the fan picture conversion device of the first embodiment. [Diagram 3] FIG. 3 is an explanatory diagram of a generated waveform in the first embodiment. [Figure 4]FIG. 4 is an explanatory diagram of the detected waveform and the generated waveform in the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Next, specific examples of the present invention (hereinafter, referred to as examples) will be described with reference to the drawings, but the present invention is not limited to the following examples. In the following description using the drawings, illustrations of components other than those necessary for the description are omitted as appropriate to facilitate understanding. EXAMPLES

[0016] FIG. 1 is an explanatory diagram of a brain stimulation device according to the present invention. 1, a brain stimulation device 1 of the present invention has a headgear 4 worn on the head 3 of a subject 2, and a computer device 6 capable of transmitting and receiving signals to and from the headgear 4. The computer device 6 has a computer main body 7, a display 8 as an example of a display unit, and a keyboard 9 and a mouse 10 as examples of an input unit.

[0017] The headgear 4 is provided with a plurality of first electrodes 11 as an example of an electroencephalogram detector. The headgear 4 is also provided with a plurality of second electrodes 12 as an example of a stimulator. The second electrodes 12 are configured to be able to apply an electric current as an example of an electrical stimulus to the head 3 in response to a control signal from the computer device 6. It is also possible to configure the first electrodes 11 and the second electrodes 12 to be shared or common to one electrode. The number of the electrodes 11, 12 is 32 (i.e., 32 channels) as an example, but the number is not limited to the illustrated numerical value and can be arbitrarily changed according to the design, specifications, etc. Although the above embodiment illustrates the case where electrical stimulation is applied by electrodes, the present invention is not limited to this. For example, it is also possible to use coils (electromagnets) and apply electrical stimulation to a specific location of the brain by electromagnetic induction caused by magnetic fields generated by multiple coils.

[0018] (Description of the control unit of the first embodiment) FIG. 2 is an explanatory diagram of the control unit of the fan picture conversion device of the first embodiment. The computer main body 7, which is an example of a control unit, has an input / output interface I / O for inputting and outputting signals from and to the outside. The computer main body 7 also has a ROM (read-only memory) in which programs and information for performing necessary processing are stored. The computer main body 7 also has a RAM (random access memory) for temporarily storing necessary data. The computer main body 7 also has a CPU (central processing unit) for performing processing according to the programs stored in the ROM or the like. Thus, the computer main body 7 can realize various functions by executing the programs stored in the ROM or the like.

[0019] (Functions of the computer main unit 7) The computer main body 7 has a function (processing means) of executing processing in response to input signals from signal output elements such as the keyboard 9, mouse 10, first electrode 11, and other sensors not shown, and outputting control signals to controlled elements such as the display 8 and second electrode 12.

[0020] The brain wave detection means C1 detects the brain waves of the subject 2 based on the input signal from the first electrode 11. The first electrode 11 and the brain wave detection means C1 constitute the electroencephalograph (11+C1) of Example 1. The electroencephalograph itself is conventionally known (see, for example, Patent Documents 1-3, etc.) and various configurations can be adopted, so detailed explanation will be omitted.

[0021] The feature extraction means C2 extracts features of the electroencephalogram pattern based on the electroencephalogram pattern (i.e., the waveform of the electroencephalogram), which is the time history of the electroencephalogram detected by the electroencephalogram detection means C1. The feature extraction means C2 of the first embodiment extracts a frequency power ratio as a feature of the electroencephalogram pattern. Specifically, the feature extraction means C2 of the first embodiment first performs filtering (band pass filtering) at a predetermined set frequency (more precisely, a "set frequency band", for example, 10 to 15 Hz) in the electroencephalogram pattern in a predetermined electroencephalogram analysis time (for example, 5 seconds). Next, for each predetermined electroencephalogram analysis time step (electroencephalogram analysis time interval, for example, 100 ms), the set frequency power and the total frequency (for example, 1 Hz to 250 Hz) power in the electroencephalogram analysis time are calculated, and the power ratio (set frequency power / total frequency power) is calculated.

[0022] FIG. 3 is an explanatory diagram of a generated waveform in the first embodiment. The waveform generating means C3 generates a waveform 16 for stimulating the brain of the subject 2 based on the features of the electroencephalogram pattern extracted by the feature extracting means C2. In FIG. 3, in the first embodiment, a waveform 16 having an envelope wave 16a corresponding to the set frequency and a higher frequency than the set frequency is generated. The frequency of the waveform 16 at this time can be, for example, a waveform 16 having a frequency five times the set frequency, but is not limited to the exemplified numerical value, and can be a high frequency of any multiple depending on the experiment, treatment results, individual differences, etc. It is preferable that the waveform 16 is a waveform having the envelope wave 16a exemplified in FIG. 3, but it is also possible to make it a sine wave corresponding to the set frequency, or a triangular wave, a sawtooth wave, a rectangular wave, etc.

[0023] FIG. 4 is an explanatory diagram of the detected waveform and the generated waveform in the first embodiment. In addition, the waveforms in FIG. 4 are explained as sine waves for ease of understanding, but the waveforms actually observed and generated are not limited to sine waves. Moreover, the waveform generating means C3 of the first embodiment calculates whether the power ratio extracted by the feature extracting means C2 exceeds a predetermined power ratio threshold (0.2 as an example). Then, based on the timing at which the power ratio exceeds the power ratio threshold, a stimulation time point, i.e., the application time (application timing) of the generated waveform is set. The waveform generating means C3 of the first embodiment generates a waveform whose phase is shifted from the phase of the waveform of the electroencephalogram pattern based on the phase shift between the electroencephalogram at the source of the electroencephalogram and the phase of the electroencephalogram at the position (position of each first electrode 11) measured by the electroencephalogram (11+C1). In FIG. 4, in the first embodiment, the waveform 21 observed by the electroencephalogram (11+C1) is shifted in phase from the waveform 22 generated at the nerve source, which is the potential generation source of the electroencephalogram, by the time it takes for the waveform 21 to reach the first electrode 11 from the nerve source. For example, the distance between the nerve source and the first electrode 11 and the volume conduction between them differ depending on the application for which the brain stimulation device 1 is used. For example, if the application is to treat depression, the source of the electroencephalogram potential is the left dorsolateral prefrontal cortex, and the distance between each first electrode 11 and the volume conduction can be used.

[0024] In the conventional configuration, a waveform 23 was formed to be synchronized with the observed waveform 21. However, when stimulating with this waveform, there was a time lag when it reached the nerve source, resulting in a phase shift as shown in waveform 24. At the nerve source, there was a risk that the phase shift would be large between waveforms 22 and 24, making it difficult to obtain the desired electrical stimulation effect. In contrast to this, in the first embodiment, a waveform 16 (indicated as an envelope wave 16a in FIG. 4) is generated with a phase shift according to the distance between the second electrode 12 and the nerve source based on the phase shift θ1 of the waveform 21 of the observed electroencephalogram. Therefore, when the generated waveform 16 (16a) reaches the nerve source, there is no phase shift with the waveform 22, and it is possible to apply the desired electrical stimulation to the nerve source. The shift θ1 is determined by the distance and volume conduction between the brain part of the potential generating source (nerve source) and the first electrode 11. The stimulation means C4 is a stimulation means for electrically stimulating the brain of the subject 2 via the second electrode 12, and applies a stimulus of the waveform 16 generated by the waveform generating means C3.

[0025] (Function of Example 1) In the brain stimulation device 1 of the embodiment 1 having the above configuration, a waveform 16 is generated according to the brain wave pattern measured by the electroencephalograph 11+C1. The waveform 16 generated in the embodiment 1 is a waveform with a phase shift of the distance between the second electrode 12 and the nerve source, according to the time lag of arrival from the nerve source to the first electrode 11. Therefore, when an electrical stimulation is applied from the second electrode 12, an electrical stimulation of a desired phase is applied in the nerve source. Therefore, in the embodiment 1, the brain can be stimulated with a signal corresponding to the phase shift of the observed brain wave. Therefore, in the conventional case, the desired effect may not be obtained due to the phase shift in the nerve source, whereas in the embodiment 1, the desired electrical stimulation can be applied in the nerve source.

[0026] In addition, in the brain stimulation device 1 of the first embodiment, when extracting the features of the electroencephalogram pattern, the power ratio of the frequency of the electroencephalogram pattern is used. When extracting features using the amplitude threshold described in Patent Document 1, if the electroencephalogram pattern contains noise, it may be erroneously determined that the threshold has been exceeded due to noise, even though the threshold has not actually been exceeded. In contrast, when the power ratio of the frequency is used, there is almost no possibility that the frequency of the noise will be the same as the set frequency, and the adverse effects of noise are suppressed compared to when the amplitude threshold is used.

[0027] Furthermore, in the brain stimulation device 1 of the first embodiment, a high-frequency wave having an envelope wave 16a of a set frequency is generated as the waveform 16. In general, the firing of nerve cells (neural activity) has a higher frequency than the observed brain waves. This is because the observed brain waves are a superposition of the firing of many nerve cells. Therefore, the brain waves measured by the electroencephalograph 11+C1 detect only low-frequency waves for the nerve activity. Therefore, in the first embodiment, in response to this, a high-frequency wave 16 is generated according to an experiment or the like for the observed brain wave pattern. Therefore, compared to the conventional technology in which only a waveform synchronized with the waveform observed by the electroencephalograph is used, it is possible to provide an effective stimulus to the nerve activity (neural firing).

[0028] (Example of change) Although the embodiments of the present invention have been described above in detail, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims. Modifications (H01) to (H07) of the present invention are illustrated below. (H01) In the above embodiment, the stimulation means C4 automatically applies stimulation based on the brain wave pattern observed by the electroencephalograph 11+C1, but the present invention is not limited to this. For example, it is possible to apply stimulation only when there is an input (external trigger) from the user. It is also possible to have only an observation mode that only observes the brain wave pattern and generates the stimulating waveform 16 without stimulating. (H02) In the above embodiment, the power ratio of the frequencies is used to extract the features of the electroencephalogram pattern, but the present invention is not limited to this. For example, the amplitude of the observed waveform 21 of the electroencephalogram pattern may be determined by a threshold value.

[0029] (H03) In the above embodiment, the set frequency can be set in advance according to the user's input or the symptoms of the treatment target, but is not limited to this. For example, it is also possible to automatically select the frequency with the greatest power in the observed waveform 21 as the set frequency. Also, the set frequency is exemplified as one case, but is not limited to this. It is also possible to use two or more set frequencies and generate the waveform 16 that is an output waveform obtained by synthesizing waveforms corresponding to the respective set frequencies. Furthermore, the set frequency is exemplified as having a predetermined width like a set frequency band, but it is also possible to set it to only a specific value without a width. (H04) In the above embodiment, it is preferable to have the envelope wave 16a, but it is also possible to have a configuration without the envelope wave 16a. That is, it is also possible to have a configuration in which the generated waveform 16 has the same frequency as the set frequency or a lower frequency than the set frequency depending on the target symptom or the stimulation that the user wants to give.

[0030] (H05) In the above embodiment, the phase of the generated waveform 16 is shifted to match the phase of the waveform 22 of the electroencephalogram generated in the nerve source, but this is not limited to this. For example, when the desired stimulation is in opposite phase to the waveform 22 of the electroencephalogram generated in the nerve source, the generated waveform 16 can be a wave whose phase is shifted by another half cycle from the phase that matches the phase of the waveform 22. In other words, the phase of the generated waveform 16 can be changed according to the phase of the desired wave to be applied to the nerve source. (H06) In the above embodiment, the first electrode 11, which is the brain wave detection unit, is configured to measure a specific set frequency, but is not limited to this. For example, it is also possible to measure a set frequency (x) with a certain electrode (11a) and another set frequency (y) with another electrode (11b).

[0031] (H07) In the above embodiment, a configuration in which the generated specific waveform 16 is applied to all of the multiple second electrodes 12 is illustrated, but this is not limited to this. For example, a configuration in which a stimulus with a waveform of a certain frequency (x') is applied to a certain electrode (12a), and a stimulus with a waveform of a different frequency (y') is applied to another electrode (12b) is also possible. In addition, a configuration in which a stimulus with a waveform with a certain phase shift (θ1) is applied to a certain electrode (12a), and a stimulus with a waveform of the opposite phase (θ1+π) is applied to another electrode (12b) is also possible. [Explanation of symbols]

[0032] 1...Brain stimulation device, 2…Subject, 11+C1…Electroencephalograph, 16...Waveforms for stimulating the brain, 16a...envelope wave, 21... EEG pattern waveform, 22... EEG at the source, C2: feature extraction means; C3...waveform generation means, C4...Stimulation means.

Claims

1. an electroencephalograph for measuring the subject's brain waves; A feature extraction means for extracting features of an electroencephalogram pattern based on an electroencephalogram pattern, which is a time history of electroencephalograms measured by the electroencephalograph; a waveform generating means for generating a waveform for stimulating the brain based on the features of the electroencephalogram pattern extracted by the feature extracting means; a stimulation means for electrically stimulating the brain of the subject, the stimulation means applying a stimulus having a waveform generated by the waveform generating means; Equipped with The waveform for stimulating the brain is a phase shift between an electroencephalogram at a source of electroencephalograms determined in advance according to a subject to be diagnosed and a phase shift between an electroencephalogram at a position measured by the electroencephalograph, the phase shift being a waveform that is shifted in phase with respect to the phase of the waveform of the electroencephalogram pattern based on the shift calculated from the distance between the source and the position measured by the electroencephalograph and volume conduction; The waveform has a higher frequency than the frequency of the electroencephalogram pattern, and A waveform enveloped by an envelope wave corresponding to the frequency of the electroencephalogram pattern. A brain stimulation device characterized by:

2. As the characteristic of the electroencephalogram pattern, a power ratio of the frequencies of the electroencephalogram pattern is used, which is calculated by dividing the power of a predetermined set frequency in the waveform of the electroencephalogram pattern by the power of all frequencies.

2. The brain stimulation device according to claim 1 .

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