Closed-loop transcranial alternating current stimulation system based on phase-amplitude coupling stimulation

Abstract

The invention discloses a closed-loop transcranial alternating current stimulation system based on phase-amplitude coupling stimulation, and the system comprises an alternating current stimulation current source which is used for generating a current signal with a fixed frequency; the stimulation and collection integrated electrode is connected with the alternating current stimulation current source and used for being worn on the head, conducting electric stimulation on a target scalp area and collecting electric signals of the target scalp area; the electroencephalogram acquisition front end is connected with the stimulation and acquisition integrated electrode and is used for acquiring electroencephalogram data according to the acquired electric signals; and the DSP processor is connected with the electroencephalogram acquisition front end and is used for executing a control algorithm according to the electroencephalogram data and adjusting parameters of the alternating current stimulation current source so as to control the stimulation and acquisition integrated electrode to perform closed-loop regulation and control on the brain. Based on the real-time electroencephalogram feedback technology, a set of closed-loop transcranial alternating current stimulation technology is constructed, phase-coupling regulation and control of the cortex are achieved, and the application range of the transcranial alternating current stimulation technology in the aspect of cognitive ability regulation and control is widened.

Description

Technical Field

[0001] The present invention relates to the technical field of transcranial alternating current stimulation, and in particular to a closed-loop transcranial alternating current stimulation system based on phase-amplitude coupling stimulation. Background Art

[0002] EEG signals are not of a single frequency, but are composed of multiple frequency oscillation components. Neurons produce neural oscillations of multiple frequencies, and their phase, amplitude and frequency interact with each other, inverting cognitive functions and disease pathological mechanisms. The cross-frequency coupling of neural electrical rhythms is called cross-frequency coupling (CFC). CFC has many forms, among which the coupling between low-frequency phase and high-frequency amplitude is phase amplitude coupling (PAC), and the coupling between theta phase and gamma amplitude is more common in PAC. The theta-gamma mode of PAC is an important indicator of functional brain network communication between the medial cortex and other brain regions, and plays an important role in the integration mechanism of cerebral cortical information transmission during different work tasks. The theta-gamma mode of PAC index is highly correlated with cognitive functions such as working memory, learning and anti-fatigue.

[0003] Transcranial electrical stimulation is a neuromodulatory technology that applies low-voltage constant or alternating current to the human brain through scalp electrodes. According to different current forms, it can be divided into transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS). Transcranial alternating current stimulation applies sinusoidal alternating current to the human brain through scalp electrodes, and affects brain function and cognitive processes by regulating brain oscillations of a specific frequency. Two electrodes are usually used, one as the positive electrode and the other as the negative electrode, and the current flows alternately between the two electrodes. The working principle of traditional tACS is to interact with endogenous neural oscillations to synchronize or decouple them from the alternating current applied from the outside, and improve related cognitive functions by regulating brain rhythms. However, traditional transcranial alternating current stimulation can only regulate neural rhythms of a single frequency, and cannot regulate the PAC effect of neural rhythms. Summary of the invention

[0004] In order to solve at least one of the technical problems existing in the prior art to a certain extent, the object of the present invention is to provide a closed-loop transcranial alternating current stimulation system based on phase-amplitude coupled stimulation.

[0005] The technical solution adopted by the present invention is:

[0006] A closed-loop transcranial alternating current stimulation system based on phase-amplitude coupled stimulation, comprising:

[0007] An alternating current stimulation current source, used to generate a current signal of a fixed frequency;

[0008] Stimulation and collection integrated electrode, connected to the AC stimulation current source, for being worn on the head to electrically stimulate the target scalp area and collect electrical signals from the target scalp area;

[0009] An EEG acquisition front end, connected to the stimulation acquisition integrated electrode, for acquiring EEG data based on the acquired electrical signals;

[0010] The DSP processor is connected to the EEG acquisition front end and is used to execute the control algorithm according to the EEG data and adjust the parameters of the AC stimulation current source to control the stimulation acquisition integrated electrode to perform closed-loop regulation on the brain;

[0011] The control algorithm includes three parts: θ rhythm bandpass filtering, calculating θ rhythm phase and adjusting γ rhythm amplitude.

[0012] Furthermore, the real-time recorded θ rhythm EEG phase signal is used as feedback to control the amplitude intensity of transcranial alternating current stimulation to achieve closed-loop PAC stimulation.

[0013] Furthermore, executing the control algorithm according to the EEG data includes:

[0014] Perform zero-phase shift bandpass filtering of theta rhythm on the EEG data of a preset time before the current moment to obtain a clean theta rhythm EEG signal;

[0015] The Hilbert transform algorithm is used to calculate the phase information of the last time point of the θ rhythm EEG signal;

[0016] The amplitude parameters of the gamma rhythm are adjusted according to the calculated phase information.

[0017] Furthermore, the corresponding relationship between the amplitude of the γ rhythm sinusoidal current source and the phase of the θ rhythm EEG signal follows the following relationship:

[0018] γ 节律幅值 =K·(cos(θ 节律相位 +α)+b)

[0019] Where K represents the amplitude constant, α represents the phase shift constant, and b represents the baseline constant.

[0020] Furthermore, a filter with a bandwidth of 4-7 Hz was used to perform zero-phase shift bandpass filtering of the theta rhythm.

[0021] Furthermore, the DSP processor executes the control algorithm once at a preset time interval.

[0022] Furthermore, the frequency of the current signal generated by the alternating current stimulation current source is 66.5 Hz.

[0023] Furthermore, the structure of the stimulation and collection integrated electrode is designed to be button-shaped, wherein the front end of the button is used to install a detachable electrode, and the detachable electrode includes a gel electrode, an Ag / AgCl electrode or a sponge electrode.

[0024] The beneficial effects of the present invention are: based on real-time EEG feedback technology, the present invention constructs a closed-loop transcranial alternating current stimulation technology, realizes phase-coupling regulation of the cortex, and broadens the application scope of transcranial alternating current stimulation technology in cognitive ability regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments of the present invention or the drawings of related technical solutions in the prior art are introduced below. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 is a schematic structural diagram of a closed-loop transcranial alternating current stimulation system based on phase-amplitude coupled stimulation in an embodiment of the present invention;

[0027] Figure 2 is a waveform diagram of the current signal output in an embodiment of the present invention;

[0028] Figure 3 This is a physical picture of the stimulation and collection integrated electrode in an embodiment of the present invention;

[0029] Figure 4 is a physical diagram of a circuit board of a closed-loop transcranial alternating current stimulation system in an embodiment of the present invention;

[0030] Figure 5 is a circuit diagram of converting an AC voltage signal output by a DSP processor into an AC current signal in an embodiment of the present invention;

[0031] Figure 6 4 is a circuit diagram for performing analog-to-digital conversion in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limitations of the present invention. For the step numbers in the following embodiments, they are only provided for the convenience of explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0033] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0034] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0035] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0036] like Figure 1 As shown, this embodiment provides a closed-loop transcranial alternating current stimulation system based on phase-amplitude coupled stimulation, comprising:

[0037] An alternating current stimulation current source, used to generate a current signal of a fixed frequency;

[0038] Stimulation and collection integrated electrode, connected to the AC stimulation current source, for being worn on the head to electrically stimulate the target scalp area and collect electrical signals from the target scalp area;

[0039] An EEG acquisition front end, connected to the stimulation acquisition integrated electrode, for acquiring EEG data based on the acquired electrical signals;

[0040] The DSP processor is connected to the EEG acquisition front end and is used to execute the control algorithm according to the EEG data and adjust the parameters of the AC stimulation current source to control the stimulation acquisition integrated electrode to perform closed-loop regulation on the brain;

[0041] The control algorithm includes three parts: θ rhythm bandpass filtering, calculating θ rhythm phase and adjusting γ rhythm amplitude.

[0042] The working mode of the system of this embodiment is as follows: during TMS stimulation, the EEG acquisition front end quantifies the scalp EEG signals recorded by the stimulation acquisition integrated electrode, processes them in real time through the DSP processor, adjusts the parameters of the AC stimulation current source, and controls the stimulation acquisition integrated electrode to perform closed-loop regulation of the brain. The DSP processor executes the control algorithm, which includes three parts: θ rhythm bandpass filtering, calculating the θ rhythm phase, and adjusting the γ rhythm amplitude.

[0043] In some embodiments, when the system is working, the AC stimulation current source outputs a sinusoidal current with a fixed frequency of 66.5Hz (γ rhythm), and the target scalp area is electrically stimulated and regulated through the stimulation acquisition integrated electrode. At the same time, the EEG acquisition front end records the original EEG data of the target scalp area through the stimulation acquisition integrated electrode and transmits it to the DSP processor. The DSP processor executes the algorithm every 10ms: (1) The EEG data of 1s before the current moment is subjected to zero-phase shift bandpass filtering of the θ rhythm (filter bandwidth: 4-7Hz) to obtain a clean θ rhythm EEG signal; (2) The Hilbert algorithm is used to calculate the phase information of the θ rhythm EEG signal at the last moment; (3) The amplitude parameter of the γ rhythm is adjusted according to the phase information. The corresponding relationship between the amplitude of the γ rhythm sinusoidal current source and the phase of the θ rhythm EEG signal follows the following relationship:

[0044] γ 节律幅值 =K·(cos(θ 节律相位 +α)+b)

[0045] Where K represents the amplitude constant, α represents the phase shift constant, and b represents the baseline constant. For example, the user can adjust these parameters before use to achieve a flexible PAC control mode. Set α = 1, b = 1, K = 1 mA, then the current output waveform is as follows Figure 2 As shown: when the theta rhythm is in the peak phase, the amplitude of the gamma rhythm current source is the largest (2 mA), and when the theta rhythm is in the trough phase, the amplitude of the gamma rhythm current source is the smallest (0 mA).

[0046] In some embodiments, see Figure 3 The integrated electrode structure for collection and stimulation is designed as a button-shaped electrode. The front end of the button can be installed with gel electrode, Ag / AgCl electrode, sponge electrode, or conductive paste, etc., to achieve diverse choices and is suitable for various experimental environments.

[0047] As an optional implementation, see Figure 4 , Figure 4This is a physical picture of the circuit board of the closed-loop transcranial alternating current stimulation system. The circuit board includes an AC stimulation current source (i.e., the stimulation module in the figure), an EEG acquisition front end (i.e., the acquisition module in the figure), and a DSP processor (i.e., the DSP in the figure). Furthermore, the circuit board also includes a PPG module, a power isolation module, and an analog interface.

[0048] See also Figure 5 ,In the AC stimulation current source part, the OPA454 operational amplifier is used to construct a ,transconductance amplifier to convert the AC voltage signal output by the DSP ,processor into an AC current signal.

[0049] See also Figure 6 ,In the front end of EEG acquisition, the ADS1299 analog-to-digital converter is used to build the front end of EEG acquisition, and the acquisition range is -375mV~375mV.

[0050] In summary, the implementation of a closed-loop transcranial alternating current stimulation system has multiple technical difficulties: during the synchronous acquisition of AC stimulation and EEG, EEG data will have large stimulation artifacts, making it difficult to perform accurate analysis and calculation; theta rhythm phase calculation needs to ensure the real-time and accuracy of the calculation. In order to achieve accurate PAC closed-loop transcranial alternating current stimulation, the system of the present invention adopts the following key technologies and achieves corresponding technical effects:

[0051] (1) The real-time recorded θ rhythm EEG phase signal was used as feedback to control the amplitude intensity of transcranial alternating current stimulation, thus achieving closed-loop PAC stimulation.

[0052] (2) An integrated acquisition and stimulation electrode is designed, which can be flexibly switched between acquisition function and stimulation function.

[0053] (3) The core algorithms used in the system are bandpass filtering and Hilbert transform. The algorithm complexity is relatively low, and a DSP controller can be used instead of a personal computer as the algorithm execution platform. No additional data communication is required, thus ensuring the real-time and portability of the system.

[0054] (4) A large-range, wide-bandwidth EEG acquisition analog front-end solution is used to ensure that the recorded EEG data is not saturated and has no nonlinear distortion.

[0055] (5) Optimize the design of the θ rhythm low-pass filter and use a zero phase shift filter to ensure that the filtered signal has no hysteresis, thereby ensuring that the real-time and accurate θ rhythm phase is obtained.

[0056] (6) While recording low-frequency EEG, high-frequency current stimulation is used. The recording frequency band (4-7 Hz) and the stimulation frequency band (66.5 Hz) are far apart. The artifact components of the electrical stimulation current can be easily removed by bandpass filtering to obtain clean EEG components.

[0057] In the above description of this specification, the description with reference to the terms "one embodiment / example", "another embodiment / example" or "certain embodiments / examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0058] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

[0059] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A closed-loop transcranial alternating current stimulation system based on phase-amplitude coupled stimulation, characterized in that: include: An alternating current stimulation current source, used to generate a current signal of a fixed frequency; Stimulation and collection integrated electrode, connected to the AC stimulation current source, for being worn on the head to electrically stimulate the target scalp area and collect electrical signals from the target scalp area; An EEG acquisition front end, connected to the stimulation acquisition integrated electrode, for acquiring EEG data based on the acquired electrical signals; The DSP processor is connected to the EEG acquisition front end and is used to execute the control algorithm according to the EEG data and adjust the parameters of the AC stimulation current source to control the stimulation acquisition integrated electrode to perform closed-loop regulation on the brain; The control algorithm includes three parts: θ rhythm bandpass filtering, calculating θ rhythm phase and adjusting γ rhythm amplitude.

2. A closed-loop transcranial alternating current stimulation system based on phase-amplitude coupled stimulation according to claim 1, characterized in that: The real-time recorded θ rhythm EEG phase signal was used as feedback to control the amplitude intensity of transcranial alternating current stimulation to achieve closed-loop PAC stimulation.

3. A closed-loop transcranial alternating current stimulation system based on phase-amplitude coupled stimulation according to claim 1, characterized in that: The executing of the control algorithm according to the EEG data comprises: Perform zero-phase shift bandpass filtering of theta rhythm on the EEG data of a preset time before the current moment to obtain a clean theta rhythm EEG signal; The Hilbert transform algorithm is used to calculate the phase information of the last time point of the θ rhythm EEG signal; The amplitude parameters of the gamma rhythm are adjusted according to the calculated phase information.

4. A closed-loop transcranial alternating current stimulation system based on phase-amplitude coupled stimulation according to claim 3, characterized in that: The corresponding relationship between the amplitude of the γ rhythm sine wave current source and the phase of the θ rhythm EEG signal follows the following relationship: c 节律幅值 =K·(cos9θ 节律相位 +a)+b) Where K represents the amplitude constant, α represents the phase shift constant, and b represents the baseline constant.

5. A closed-loop transcranial alternating current stimulation system based on phase-amplitude coupled stimulation according to claim 3, characterized in that: Zero-phase-shift bandpass filtering of the theta rhythm was performed using a filter with a bandwidth of 4-7 Hz.

6. A closed-loop transcranial alternating current stimulation system based on phase-amplitude coupled stimulation according to claim 1, characterized in that: The DSP processor executes the control algorithm once at every preset time interval.

7. A closed-loop transcranial alternating current stimulation system based on phase-amplitude coupled stimulation according to claim 1, characterized in that: The frequency of the current signal generated by the alternating current stimulation current source is 66.5 Hz.

8. A closed-loop transcranial alternating current stimulation system based on phase-amplitude coupled stimulation according to claim 1, characterized in that: The structure of the stimulation and collection integrated electrode is designed to be button-shaped, wherein the front end of the button is used to install a detachable electrode, and the detachable electrode includes a gel electrode, an Ag / AgCl electrode or a sponge electrode.

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