EEG-fNIRS signal acquisition device and related system

Abstract

The invention discloses an EEG-fNIRS signal acquisition device and a related system, and relates to the technical field of biological intelligent sensing, and the signal acquisition device mainly comprises an EEG dry electrode, a near-infrared light source, a near-infrared light detector, a flexible signal transmission board and a control circuit. The distribution of a light source and a detector of the fNIRS adopts a bipolar detector distribution structure and a light source sharing mode; two electrodes, used for differential amplification, of the EEG are distributed between a light source and a detector of the fNIRS, the signal quality is improved, meanwhile, the space is reasonably utilized, and synchronous collection of the EEG and the fNIRS at the same node is achieved. According to the signal acquisition device provided by the invention, on the basis of advantage complementation of EEG and fNIRS data in time resolution and spatial resolution, EEG-fNIRS signals are acquired at the same time, so that the information quality is improved; a high-density structural design is achieved, and the information bandwidth is improved; the same-node acquisition enables a researcher to observe the interrelation between EEG and fNIRS, and a new material is provided for brain science and neuromedicine research.

Description

Technical Field

[0001] The present invention relates to the field of biological intelligent sensing technology, and in particular to an EEG-fNIRS signal acquisition device and a related system. Background Art

[0002] EEG and fNIRS are two important methods in the field of cognitive neuroscience research and emotional interaction. EEG signals have higher temporal resolution. However, due to the electrical conduction characteristics, the spatial resolution of electrical signals is low, and it is difficult to decode the spatial vector of EEG signals on the body surface; fNIRS signals calculate blood oxygen fluctuations based on the light attenuation law of the local area, and have higher spatial resolution.

[0003] The EEG-fNIRS-based monitoring device achieves an effective combination of the two signals. On the one hand, it improves the accuracy of the characteristic neural network. On the other hand, the differential changes in the two signals also provide richer information for research in the field of neuroscience.

[0004] Nerve activation consumes oxygen to supply energy to neurons, and the content of neurons forms a potential difference, generating regular electrical signals. Discharge and blood oxygen changes are in the same space and frequency. However, the current EEG-fNIRS node synchronization is still insufficient, which makes the feature model less interpretable. On the other hand, after the two are combined, the control circuit is more complicated, and the signals interfere with each other, resulting in the wearing comfort and accuracy not meeting the needs of emotional interaction. For example, Zhang Xueying disclosed an EEG-fNIRS electrode arrangement method and system based on brain region division in the invention patent CN116269389A. , the electrode types and arrangement order of the electrodes arranged in each of the divided brain regions are determined as follows: the EEG electrodes are arranged in the frontal lobe region, the temporal lobe region, the central region, the parietal lobe region and the occipital lobe region; the fNIRS electrodes are arranged in the frontal lobe region and the temporal lobe region; in the frontal lobe region and the temporal lobe region, the fNIRS electrodes and the EEG electrodes do not overlap; that is, the area to be detected is first determined, and then the detection electrodes of the purchased equipment are arranged at intervals. This invention patent can simultaneously collect fNIRS and EEG signals in a large area, such as the frontal lobe, but the channels do not form a one-to-one correspondence, and it is difficult to directly compare the fNIRS and EEG information of a certain node. When two independent EEG and fNIRS systems are used at the same time, the time synchronization of the two signals is also relatively low. Summary of the invention

[0005] The present invention provides an EEG-fNIRS signal acquisition device and a related system. The problem of poor synchronization of signal nodes of EEG-fNIRS devices in the field of emotional interaction is solved by arranging EEG electrodes in the gap between the light source and the detector of fNIRS; and the two modules interact using the same control circuit to solve the problem of poor time synchronization.

[0006] To achieve the above-mentioned object, the technical solution of the present invention provides an EEG-fNIRS signal acquisition device, which includes an fNIRS bipolar detector, an fNIRS light source, an EEG acquisition channel and a flexible signal transmission board; Preferably, a plurality of the fNIRS bipolar detectors and fNIRS light sources are cross-arranged on the flexible signal transmission board in the order of fNIRS bipolar detector-fNIRS light source; the EEG acquisition channel is provided between adjacent fNIRS bipolar detectors and fNIRS light sources; the two detectors in one fNIRS bipolar detector share one fNIRS light source, thereby improving the space utilization of the system, reducing power consumption, shortening the time period of fNIRS light source control, and improving the sampling rate; the fNIRS bipolar detector is composed of two independent fNIRS detectors closely connected, and the two closely connected independent fNIRS detectors are on the same side of the fNIRS light source and at different distances from the fNIRS light source, so as to amplify and increase the amount of information in each channel.

[0007] Preferably, the EEG acquisition channel adopts a differential amplification dual electrode, and one EEG acquisition channel comprises a positive electrode and a negative electrode, and the positive and negative electrodes are vertically arranged between the fNIRS bipolar detector and the fNIRS light source.

[0008] Preferably, both electrodes of the EEG acquisition channel can be reused as a reference electrode and a right leg bias electrode.

[0009] Preferably, the flexible signal transmission board is further provided with a transversely arranged EEG acquisition channel, and two electrodes of the transversely arranged EEG acquisition channel are respectively arranged between two front and rear adjacent groups of the fNIRS light sources and the next fNIRS bipolar detector.

[0010] Preferably, the two electrodes of the horizontally arranged EEG acquisition channel can be reused as a reference electrode and a right leg bias electrode, and can also be reused as a transcranial electrical stimulation electrode interface to connect external physiotherapy electrodes.

[0011] Preferably, the flexible signal transmission board includes an fNIRS flexible signal transmission board and an EEG flexible signal transmission board, and the fNIRS flexible signal transmission board and the EEG flexible signal transmission board are nested together front and back.

[0012] Preferably, the surface of the flexible signal transmission board is covered with a signal shielding film and aluminum foil to reduce interference from power frequency signals. The electrodes are fixed to the EEG flexible signal transmission board by copper screws, and a pure copper gasket is also included between the copper screws and the EEG flexible signal transmission board to secure the electrodes to the EEG flexible signal transmission board. The fNIRS flexible signal transmission board also has a reinforcement plate on the back of the fNIRS light source and the fNIRS detector.

[0013] The present invention also provides an EEG-fNIRS signal acquisition system, comprising: a control circuit and an EEG-fNIRS signal acquisition device.

[0014] Preferably, the control circuit comprises: a power supply unit, an EEG module, an fNIRS module, a system control module, and a communication unit. The EEG module and the communication module are both provided with independent reference grounds, which are isolated from the reference grounds of other modules to avoid mutual interference of digital signals.

[0015] Compared with the prior art, the present invention can at least achieve the following beneficial effects: The light source and detector distribution of fNIRS adopts a bipolar detector distribution structure and a light source sharing method; the dual electrodes used for differential amplification of EEG are distributed between the light source and detector of fNIRS, which not only improves the signal quality, but also makes rational use of space and realizes the synchronous acquisition of EEG and fNIRS at the same node. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the electrode arrangement of an EEG-fNIRS signal acquisition device for prefrontal lobe monitoring provided in an embodiment of the present invention.

[0017] Figure 2 This is a structural block diagram of an EEG-fNIRS signal acquisition system provided in an embodiment of the present invention.

[0018] Figure 3 A schematic diagram of the structure of an EEG-fNIRS signal acquisition device provided in an embodiment of the present invention.

[0019] Figure 4 A physical diagram of an EEG-fNIRS signal acquisition device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0021] In order to better reflect and express the core solution of the present invention, the embodiment of the present invention first takes the collection of prefrontal EEG-fNIRS signals as an example, and specifically provides an electrode arrangement design method for an EEG-fNIRS signal collection device for prefrontal monitoring.

[0022] Please refer to Figure 1 ,like Figure 1 The figure shows a schematic diagram of the electrode arrangement of an EEG-fNIRS signal acquisition device for prefrontal lobe monitoring provided by an embodiment of the present invention. In the figure, "D" represents the detector, "S" represents the light source; "digital +" represents the positive input electrode of the EEG, and "digital -" represents the negative input electrode of the EEG.

[0023] The fNIRS signal acquisition part of the EEG-fNIRS signal acquisition device for prefrontal lobe monitoring specifically includes, from the wearer's perspective (arranged in sequence from left to right): a first detector D1, a second detector D2, a first light source S1, a third detector D3, a fourth detector D4, a second light source S2, a fifth detector D5, a sixth detector D6, and a third light source S3; wherein the first detector D1 and the second detector D2 are both on the same side of the first light source S1, constituting a first fNIRS bipolar detector, sharing the first light source S1; the third detector D3 and the fourth detector D4 are both on the same side of the second light source S2, constituting a second fNIRS bipolar detector, sharing the second light source S2; the third detector D5 and the fourth detector D6 are both on the same side of the third light source S3, constituting a third fNIRS bipolar detector, sharing the third light source S3.

[0024] This bipolar structural design can increase the amount of information in each channel without increasing the coverage area of ​​a single channel. Two adjacent fNIRS channels share one fNIRS light source, which improves the space utilization of the system and reduces power consumption. At the same time, it shortens the time period of fNIRS light source control and increases the sampling rate.

[0025] The detection depth of fNIRS is correlated with the distance between the detector and the light source. When the distance between the near-infrared light source and the detector is about twice the maximum depth that the emitted near-infrared light signal can detect, it can ensure that the near-infrared signal emitted by the near-infrared light source can detect the target area and retain a strong light signal intensity to be received by the detector. Since the depth from the forehead surface to the cortex of the human body is generally 10 mm, as a preferred embodiment, the distance from the fNIRS bipolar detector to the corresponding light source is 20 mm, and the distance between the two detectors in the fNIRS bipolar detector is 5 mm.

[0026] The four channels of the EEG electrode of the EEG-fNIRS signal acquisition device for frontal lobe monitoring are distributed between the light source and the detector of the fNIRS, which improves the space utilization rate and ensures that the spatial positions of the EEG electrode and the fNIRS detection channel correspond one to one, so as to realize the synchronous acquisition of EEG-fNIRS common nodes. The same number represents the corresponding channel, "1+", "1-" represents the channel 1 of EEG, "2+", "2-" represents the channel 2 of EEG, "3+", "3-" represents the channel 3 of EEG, and "4+", "4-" represents the channel 4 of EEG. The EEG signal acquisition part specifically includes: EEG channel 1, vertically arranged at the midpoint of the second detector D2 and the first light source S1; EEG channel 2, vertically arranged at the interval between the fourth detector D4 and the second light source S2, with the axis and the second light source S2; EEG channel 3, vertically arranged at the midpoint of the sixth detector D6 and the third light source S3; EEG channel 4, arranged horizontally, with the positive electrode placed at the midpoint of the first light source S1 and the third detector D3, and the negative electrode placed at the midpoint of the second light source S2 and the fifth detector D5.

[0027] Based on the understanding of the structure of the human forehead, as a preferred embodiment, the center distance between the two electrodes of the vertically arranged EEG channel is 15 mm. On the one hand, it can avoid the positive and negative electrodes of the EEG being too tight, thereby reducing the stability of the collected information; on the other hand, due to the different thicknesses of the electrodes and the light source detector, the 15 mm spacing can ensure that the collection device has enough space to bend and stick to the human forehead.

[0028] The two electrodes of any EEG channel can be reused as a reference electrode and a right leg bias electrode. This design is conducive to expanding the flexibility of the EEG part. At the same time, in a complex usage environment, the right leg bias electrode can improve the anti-interference ability of the system.

[0029] The two electrodes of EEG channel 4 can also be reused as transcranial electrical stimulation electrodes and externally connected to physical therapy electrodes. This design can intervene in the wearer's frontal lobe state at any time according to the test results, expanding the scope of use of the device.

[0030] fNIRS uses the attenuation data of near-infrared light in tissue to calculate the relative values ​​of oxygenated hemoglobin and deoxygenated hemoglobin. There are two unknown variables, so at least two known variables need to be used for calculation, so at least two wavelengths of near-infrared light are required. Preferably, the light source used in this embodiment can emit near-infrared light of two wavelengths, 660nm and 905nm. The detector converts the light intensity signal collected after penetrating the tissue into an electrical signal, and the frequency of the signal is proportional to the light intensity. The light source is powered by a 3.3V power supply, and the two pins are powered alternately to achieve the conversion of the two near-infrared lights.

[0031] Please refer to Figure 2 ,like Figure 2 , which is a schematic diagram of the system structure of an EEG-fNIRS signal acquisition system provided by an embodiment of the present invention.

[0032] The EEG-fNIRS signal acquisition system consists of a signal acquisition device with EEG electrodes, fNIRS light source and fNIRS detector arranged in the front, as well as a control circuit.

[0033] The control circuit consists of a power supply unit, a communication unit, a system control module, an EEG module and an fNIRS module.

[0034] The system control module consists of a main control chip and surrounding circuits, and is powered by a 3.3V voltage source provided by the power supply unit. It is responsible for controlling the other four modules of the control circuit. The EEG module and fNIRS module are uniformly controlled by one MCU, which reduces the manufacturing cost, improves the synchronization of the two systems, reduces the overall circuit complexity, and is more suitable for wear. The power supply unit consists of a system power supply circuit and a reference voltage circuit. The system power supply circuit supplies power to the entire system and the reference voltage circuit. The ground wire of the power supply circuit is connected to the digital ground. The ground wire of the reference voltage circuit is connected to the analog ground. This method of separating the system power supply circuit from the reference voltage circuit can reduce the mutual interference between digital signals and analog signals and improve the stability of EEG signals. The reference voltage circuit EEG module consists of a signal amplification circuit, a multiplexing circuit and a digital-to-analog conversion circuit. The working voltage is provided by the power supply circuit, and the reference voltage is provided by the reference voltage circuit. The EEG module is connected to the analog ground, and the analog ground is isolated from the digital ground to avoid mutual interference between EEG analog signals.

[0035] The signal amplification circuit is responsible for amplifying the collected EEG signal according to the amplification factor, and the specific amplification factor can be set through the main control chip.

[0036] The multiplexing circuit can control the working mode of the EEG module, including: short-circuit mode, which is used to measure the internal noise of the system; test signal mode, which can generate analog signals inside the system for testing and measuring the internal noise of the system; and normal acquisition mode, which normally acquires EEG signals.

[0037] The digital-to-analog conversion circuit converts the collected analog signal into a digital signal and transmits it to the system control module.

[0038] The fNIRS module consists of an fNIRS light source circuit and an fNIRS detector circuit.

[0039] The fNIRS light source circuit contains three independent light source control circuits, each of which consists of a voltage regulator and a fast switch. The two pins of each fNIRS light source are connected to the two output pins of the fast switch. By switching the input of the two pins, the wavelength mode is controlled. The voltage regulator is connected to the main control chip. The PWM signal output by the main control chip is amplified by the voltage regulator and output to the fast switch. The high and low voltage signals of PWM determine the on and off state of the fast switch, realizing the control of the output light intensity.

[0040] The fNIRS detector is powered by a 3.3V voltage source and converts the collected light intensity signal into a digital signal. The number of times the high voltage appears in the digital signal per unit time is proportional to the light intensity.

[0041] The detector will detect all the light signals returned from the tissue, so in order to avoid interference of light signals between fNIRS channels, the light source and detector should be switched on and off according to the specific acquisition frequency. For example, when detecting the blood oxygen fluctuation between the first light source and the first detector, the other light sources and detectors should be temporarily disconnected.

[0042] The communication unit consists of a WIFI circuit, a Bluetooth circuit and a serial port circuit. During use, the data transmission mode can be flexibly selected to adapt to more usage scenarios.

[0043] The communication unit is connected to the digital ground, but an independent area needs to be divided and connected to the digital ground only through a 0.3mm copper wire. This prevents the communication unit from transmitting signals using WIFI and Bluetooth, where part of the signal is absorbed by the grounding copper plate of the communication unit, causing current fluctuations and interfering with other modules.

[0044] Please refer to Figure 3 and Figure 4 ,like Figure 3 and 4 , which is a schematic diagram of an EEG-fNIRS signal acquisition device provided in an embodiment of the present invention. Figure 3 For line graph display, Figure 4 This is the actual assembly effect.

[0045] The electrodes, light sources and detectors are independently arranged on two flexible signal transmission boards. The signal transmission board of the electrode is behind the signal transmission board of the light source and the detector. Through punching holes in the signal transmission board, all electrodes, light sources and detectors are attached to the skin at the same time.

[0046] EEG uses dry electrodes with silver chloride coating. They are fixed to the FPC flexible signal transmission board with copper screws. In order to firmly fix the electrodes, pure copper gaskets with a thickness of 0.5mm are added between the screws and the signal transmission board. A soldering pad with a radius of 3mm is added to the part where the flexible signal transmission board contacts the electrode. The copper sheet and the soldering pad are tightened and fixed by copper screws, and will not move during wearing. This design improves the stability of signal conduction and makes the copper sheet and the soldering pad in close contact.

[0047] The surface of the flexible signal transmission board is covered with signal shielding film and aluminum foil to reduce the interference of power frequency signals.

[0048] The flexible signal transmission board adds reinforcement plates on the back of the light source and detector to improve the strength of the components and prevent the pins from detaching from the circuit board due to bending when worn on tissues with large curvature.

[0049] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments. According to the disclosure and teaching of the above specification, those skilled in the art to which the present invention belongs may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. According to the disclosure and teaching of the above specification, those skilled in the art to which the present invention belongs may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention.

Claims

1. An EEG-fNIRS signal acquisition device, characterized in that: Includes fNIRS bipolar detector, fNIRS light source, EEG acquisition channel and flexible signal transmission board; The plurality of fNIRS bipolar detectors and fNIRS light sources are cross-arranged on the flexible signal transmission board in the order of fNIRS bipolar detectors-fNIRS light sources; the EEG acquisition channel is arranged between adjacent fNIRS bipolar detectors and fNIRS light sources; Two detectors in one fNIRS bipolar detector share one fNIRS light source.

2. The EEG-fNIRS signal acquisition device according to claim 1, characterized in that: The fNIRS bipolar detector is composed of two independent fNIRS detectors that are closely connected. The two independent fNIRS detectors that are closely connected are located on the same side of the fNIRS light source and at different distances from the fNIRS light source.

3. The EEG-fNIRS signal acquisition device according to claim 1, characterized in that: The EEG acquisition channel adopts a differential amplification dual electrode, and one EEG acquisition channel includes a positive electrode and a negative electrode, and the positive and negative electrodes are vertically arranged between the fNIRS bipolar detector and the fNIRS light source; the flexible signal transmission board is also provided with a horizontally arranged EEG acquisition channel, and the two electrodes of the horizontally arranged EEG acquisition channel are respectively arranged between two adjacent groups of fNIRS light sources and the next fNIRS bipolar detector.

4. The EEG-fNIRS signal acquisition device according to claim 3, characterized in that: The two electrodes of the EEG acquisition channel can be reused as a reference electrode and a right leg bias electrode; the two electrodes of the horizontally arranged EEG acquisition channel can be reused as a reference electrode and a right leg bias electrode or reused as a transcranial electrical stimulation electrode interface, and externally connected to a physiotherapy electrode sheet.

5. The EEG-fNIRS signal acquisition device according to claim 1, characterized in that: The flexible signal transmission board includes an fNIRS flexible signal transmission board and an EEG flexible signal transmission board, and the fNIRS flexible signal transmission board and the EEG flexible signal transmission board are nested in one body front and back.

6. The EEG-fNIRS signal acquisition device according to claim 5, characterized in that: The surface of the flexible signal transmission board is covered with a signal shielding film and aluminum foil to reduce interference with power frequency signals.

7. The EEG-fNIRS signal acquisition device according to claim 5, characterized in that: The electrode is fixed on the EEG flexible signal transmission board by a copper screw, and a pure copper gasket is also included between the copper screw and the EEG flexible signal transmission board to firmly secure the electrode on the EEG flexible signal transmission board.

8. The EEG-fNIRS signal acquisition device according to claim 1, characterized in that: The fNIRS flexible signal transmission board is further provided with a reinforcement plate on the back of the fNIRS light source and the fNIRS detector.

9. An EEG-fNIRS signal acquisition system, characterized in that: include: The EEG-fNIRS signal acquisition device according to any one of claims 1 to 8, used to acquire EEG-fNIRS signals of the human frontal lobe; The control circuit is used to control the working mode of the EEG-fNIRS signal acquisition device, collect and send the EEG-fNIRS signals collected by the EEG-fNIRS signal acquisition device, and power the system.

10. The EEG-fNIRS signal acquisition system according to claim 9, characterized in that: The control circuit comprises: A power supply unit, used to power the system and provide a stable reference voltage for the EEG module; EEG module, used to amplify the collected EEG signal, calculate the common mode voltage, eliminate common mode interference, and provide test signals; The fNIRS module is used to control the on-off timing of the fNIRS light source, the rapid switching of the light source, and convert the collected light signal into a digital signal; A system control module, used to receive data sent back by the EEG module and the fNIRS module, manage the working modes of the EEG module and the fNIRS module, and regularly detect the power supply; The communication unit is used to verify the data collated by the system control module and send it to other devices through the serial port, WiFi or Bluetooth.

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