A pseudo-wave suppressor for neural stimulation and recording systems

Abstract

The present invention proposes and implements a pseudo-wave suppressor for a neural stimulation and recording system to suppress pseudo-waves generated during the stimulation process that seriously affect the recording quality. The pseudo-wave suppressor has a three-electrode structure, and achieves a complementary state of the reference voltage through the resistors connected between the electrodes and an adjustable current generator, so that pseudo-waves generated by excessive fluctuations in the stimulation voltage can be eliminated at the recording point. The pseudo-wave suppressor has two main advantages: one is that it can suppress pseudo-waves in real time and is low-cost; the other is that it has no blank time and is suitable for multi-channel applications.

Description

Technical Field

[0001] The present invention specifically relates to a pseudo wave suppressor for a neural stimulation and recording system, and belongs to the technical field of integrated circuits. Background Art

[0002] In recent decades, stimulators have been widely used in the biomedical field, such as pacemakers, cochlear implants / retina, functional electrical stimulation, and cell activation and culture. Neural recording is an important basis for triggering signals for stimulators and evaluating the effects of stimulation. In this bidirectional system, the pseudo-waves caused by stimulation become the most difficult problem faced by researchers, because pseudo-waves are overwhelmingly large compared to neural signals, and they saturate the recording channels for a long time during and after stimulation. At present, the more popular methods for suppressing pseudo-waves include signal post-processing, resetting recording channels, local stimulation, etc. These methods will more or less consume extra time and space, and will also have long blanks on the recording channels, which are not suitable for real-time, low-cost, multi-channel recording systems. The present invention proposes a differential stimulator without signal processing to suppress pseudo-waves generated by fluctuations in stimulation voltage in real time. Summary of the invention

[0003] OBJECT OF THE INVENTION: The object of the present invention is to reduce the effects of large stimulation voltage fluctuations on remote recording electrodes.

[0004] A pseudo-wave suppression stimulator for a neural stimulation and recording system, characterized in that it comprises a three-electrode electrode structure consisting of an electrode WE1 (106), an electrode WE2 (107), and an electrode RE (109). A resistor RL1 (104) is connected between the electrode W E1 (106) and the electrode RE (109), the resistor R L2 (105) is connected to electrode W E2 (107) and electrode RE (109), the stimulation current (100) is connected to electrode WE1 (106), the injection current (101) is connected to electrode WE2 (107), and the reference voltage V ref (102) is connected to the electrode RE (109), and the neural recorder AMP (103) records the neural signal at the distal end of the tissue (108)

[0005] Furthermore, the device for generating the stimulation pull current (100) supplies current to the electrode WE1 (106), and the current flows into the nerve tissue (108) to generate nerve stimulation, and generates a forward voltage drop across the resistor RL1 (104). The stimulation injection current (101) generates a current with a phase opposite to that of the stimulation pull current (100), thereby generating a reverse voltage drop across the resistor RL2 (105). When the stimulation voltage on the electrodes WE1 (106) and WE2 (107) is transmitted to the remote neural recorder AMP (103), due to the offset effect of the forward voltage and the reverse voltage, the voltage at the recording point can be maintained constant, suppressing the generation of pseudo waves.

[0006] Furthermore, both the stimulation pull current (100) and the injection current (101) are adjustable. Each time the nerve is stimulated, the magnitude of the stimulation pull current (100) is fixed, and then the magnitude of the injection current (101) is adjusted to achieve the voltage offset effect of the two working electrodes.

[0007] Furthermore, the compensation effect of the injection current (101) is reflected in ensuring that the forward voltage of the electrode WE1 (106) and the reverse voltage of the electrode WE2 (107) can offset each other. L1 (104) and R L2 The value of (105) is a fixed parameter generated under the stimulation state and has no ability to be adjusted. Ideally, when the resistor RL1 (104) and the resistor RL2 (105) are the same, the magnitudes of the stimulation pull current (100) and the injection current (101) are equal, and the voltage waveforms on the electrode WE1 (106) and the electrode WE2 (107) can be offset. In practical applications, the impedance of the resistor RL1 (104) and the resistor RL2 (105) will have a certain difference, so the magnitude of the injection current (101) and the stimulation pull current (100) cannot be kept consistent. By connecting the electrodes WE1 (106) and WE2 (107) to an oscilloscope, the voltage waveforms on the electrodes can be observed. Once it is found that the voltage amplitudes of the two are different, the magnitude of the injection current (101) is adjusted to ensure that the voltage waveform of the electrode WE2 (107) and the voltage waveform of the electrode WE1 (106) have the same amplitude and opposite phase.

[0008] The object of the present invention is achieved by the following measures:

[0009] Figure 1 The structure diagram of the pseudo wave suppression stimulator is shown in FIG. An electrode 109 is placed between the electrode 106 of the stimulation current source 100 and the electrode 107 of the current sink 101. The electrode 106 and the electrode 109 are connected by a resistor 104; the electrode 107 and the electrode 109 are connected by a resistor 105. Thus, a pseudo wave suppression stimulator structure is formed.

[0010] At present, the main solutions to reduce the influence of spurious waves include signal post-processing, resetting the recording channel and local stimulation. These solutions are either time-consuming or have a blank time of hundreds of microseconds to several milliseconds on the recording channel, which is not suitable for real-time, economical, multi-channel bidirectional recording and stimulation systems. Compared with these traditional methods, the present invention has the function of suppressing spurious waves in real time, and is stable, fast and cost-saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is the circuit diagram of the pseudo-wave suppression stimulator unit.

[0012] Among them: 100 is the stimulation pull current; 101 is the injection current; 102 is the reference voltage; 103 is the neural recorder; 104 is the resistor 1; 105 is the resistor 2; 106 is the working electrode 1; 107 is the working electrode 2; 108 is the human tissue; 109 is the reference electrode. DETAILED DESCRIPTION

[0013] According to the aforementioned invention, the circuit structure was constructed in Cadence by applying the 0.18 μm process provided by Taiwan Semiconductor Manufacturing Co., Ltd. (TSMC), and the design of the above structure was verified to be highly feasible by simulation.

[0014] In order to eliminate stimulation artifacts caused by voltage fluctuations of the stimulation electrodes, three electrodes are used in one stimulation channel: 106, 107, and 109. A reference electrode 109 is placed between 106 and 107 to form a symmetrical three-pole electrode. Under ideal load conditions where the impedances of resistors 104 and 105 are the same, the stimulation voltage waveforms on electrodes 106 and 107 become complementary due to this symmetrical electrode structure. Using the basic principle of voltage superposition, artifacts caused by stimulation current are eliminated at the recording point.

[0015] In actual applications, resistor 104 and resistor 105 are slightly different due to mismatch. To solve this problem, an adjustable current sink 101 is set here to compensate for the improper impedance matching to keep the voltages on electrode 106 and electrode 107 complementary. In the simulation, the stimulation source current 100 and the current sink 101 are added at the same time, and the reference voltage 102 and the recording point voltage are observed to determine that this structure can make the output voltage stable.

[0016] Therefore, by comparing the results, it can be found that the pseudo-wave suppressor constructed by the above structure can eliminate the pseudo-waves generated by excessive stimulation intensity, thereby reducing the error at the recording point.

Claims

1. A pseudo-wave suppression stimulator for a neural stimulation and recording system, characterized in that: The invention comprises a three-electrode electrode structure consisting of an electrode WE1 (106), an electrode WE2 (107), and an electrode RE (109); a resistor RL1 (104) is connected between the electrode WE1 (106) and the electrode RE (109); a resistor RL2 (105) is connected between the electrode WE2 (107) and the electrode RE (109); a stimulation pull current (100) is connected to the electrode WE1 (106); a pouring current (101) is connected to the electrode WE2 (107); a reference voltage V ref (102) is connected to the electrode RE (109), and the neural recorder AMP (103) records the neural signal at the distal end of the tissue (108); The device for generating the stimulation pull current (100) supplies current to the electrode WE1 (106), and the current flows into the nerve tissue (108) to generate nerve stimulation and generate a forward voltage drop across the resistor RL1 (104); the stimulation injection current (101) generates a current with a phase opposite to that of the stimulation pull current (100), thereby generating a reverse voltage drop across the resistor RL2 (105); when the stimulation voltage on the electrodes WE1 (106) and WE2 (107) is transmitted to the remote neural recorder AMP (103), due to the offset effect of the forward voltage and the reverse voltage, the voltage at the recording point can be maintained constant, thereby suppressing the generation of pseudo waves; Both the stimulation pull current (100) and the injection current (101) are adjustable. Each time nerve stimulation is performed, the size of the stimulation pull current (100) is fixed, and then the size of the injection current (101) is adjusted to achieve the voltage offset effect of the two working electrodes.

2. The stimulator according to claim 1, characterized in that: The compensation effect of the injection current (101) is reflected in ensuring that the forward voltage of the electrode WE1 (106) and the reverse voltage of the electrode WE2 (107) can offset each other; the values ​​of the resistors RL1 (104) and RL2 (105) are fixed parameters generated under the stimulation state and have no ability to be adjusted; Ideally, when the resistor RL1 (104) and the resistor RL2 (105) are the same, the magnitudes of the stimulation pull current (100) and the injection current (101) are equal, and the voltage waveforms on the electrode WE1 (106) and the electrode WE2 (107) can be offset; in actual applications, there will be a certain difference in the impedance of the resistor RL1 (104) and the resistor RL2 (105), so the magnitudes of the injection current (101) and the stimulation pull current (100) cannot be consistent; by connecting the electrodes WE1 (106) and WE2 (107) to an oscilloscope, the voltage waveforms on the electrodes can be observed; once it is found that the voltage amplitudes of the two are different, the magnitude of the injection current (101) is adjusted to ensure that the voltage waveform of the electrode WE2 (107) and the voltage waveform of the electrode WE1 (106) have the same amplitude and opposite phase.

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