RU182738U1 - Dry active electrode for neurocomputer interface - Google Patents

Abstract

The utility model relates to medical equipment, in particular, to devices for recording information about brain activity or the functional state of the human brain during studies by electroencephalography for subsequent use of the data obtained in the field of neurocomputer interface. Provides improved signal quality of electrical brain activity during electroencephalography non-invasive method without the use of additional electrically conductive contact medium. The device includes an electrically conductive current collector 1, which has external protrusions 2 and a contact connector 3. The contact connector 3 is configured to be mechanically located in the mate 4 of the contact 3. The connector 3 and its mate are secured against accidental loss, for example, in the form of a “button for clothes” connection. The electrode contains a housing 5 and an electronic module 6. An electronic module 6 is housed in the housing 5. The counterpart 4 of the connector 3 is mounted on the electronic module 6. The electronic module 6 includes a protective resistor 7 connected to an operational amplifier 8 and an analog key 9. Analog key 9 made with the possibility of receiving an external control signal, 9 z.p. f-ly, 4 ill.

Description

The utility model relates to medical equipment, in particular, to devices for recording information about brain activity or the functional state of the human brain during studies by electroencephalography for subsequent use of the data obtained in the field of neurocomputer interface.

Neurocomputer Interface (NCI) (also called direct neural interface, brain interface, brain-computer interface, BCI-brain-computer interface) is a system designed to exchange information between the brain and an electronic device (e.g. computer). It allows the user to interact with the outside world without the help of nerves and muscles, only with the help of control signals generated by his brain activity through one-way or two-way communication between the brain and the electronic device.

At the moment, thanks to NCI, it has become possible to communicate with paralyzed patients, as well as neuro prosthetics and the treatment of certain diseases. For research purposes, the neurocomputer interface allows you to find out which parts of the brain are responsible for visual, emotional perception, etc. In the gaming industry, experiments are conducted where subjects play on a computer using electrical brain signals.

The neurocomputer interface detects patterns of activation of activity in the brain that correspond to the desired human action. Whenever the user changes them, the neurocomputer interface in response is able to translate the new patterns into action corresponding to the will of the user. Recognizing a specific set of patterns includes the following steps: receiving a signal, preprocessing, interpreting and classifying the data.

One of the directions of existing technologies for receiving signals from electrical brain activity is the non-invasive method, which consists in removing external signals (mainly pulses of brain activity) from the human scalp using external electrodes. This method is known as electroencephalography (EEG). Non-invasive EEG methods are used in neurocomputer interface applications because they provide acceptable signal quality combined with low cost and ease of use.

As a rule, an electroencephalogram (EEG) is recorded from the surface of the head using electrodes by means of a special gel, which is an additional electrically conductive contact medium. One of the main advantages of conducting EEG studies using a gel is the reliability of their contact with the scalp and the quality of the received signal. However, there are drawbacks to its use - the long installation time of the electrodes, the need to clean the electrodes after each use and hair after recording, drying of the electrically conductive gel with a long study. In some situations, these shortcomings adversely affect research results. For example, in mass studies of brain functions, in the diagnosis of neurological disorders in children, especially when conducting studies at night, during long-term studies, when monitoring the state of resuscitation patients, as well as when used in everyday (non-clinical) conditions in everyday life in particular to control a wheelchair, or to move a prosthesis of a person’s limb or to reproduce text on the screen of an electronic device with the help of thought, that is, when of everyday mental tasks.

Therefore, there was a need to create the so-called "dry" electrodes, which would provide an acceptable signal transmission quality without the use of an additional electrically conductive contact medium.

A dry active electrode for a neurocomputer interface is known from the prior art, including an electrically conductive current collector having external protrusions and a contact connector configured to mechanically be placed in the contact part of the contact connector (see, for example, http://www.gtec.at /Products/Electrodes-and-Sensors/g.SAHARA-Specs-Features). The execution of the current collector removable allows for the control of its contamination to provide quick replacement with a new one, which affects the reliability of electrical contact with the scalp. In addition, a removable electrode provides hygiene and allows the use of electrodes by different people. However, the disadvantage of the described device is the insufficiently high quality of registration of signals of electrical brain activity due to the distance from the electrode of the active part - the amplifier. The signal from the electrode is transmitted by wire to the EEG amplifier, which is connected to the signal processing device or built into it. Electromagnetic interference caused by any other equipment located nearby and mechanical interference caused by the movement or vibration of the EEG electrode wire do not allow the transmitted signal to maintain its amplitude and shape in the initial form taken from the person’s head, which significantly affects the reliability of further processing this signal, and, therefore, on the quality of research. In addition, this technical solution does not provide for monitoring the correct positioning of the electrode on the human head and the adequacy of the contact of the electrode with the scalp, which in turn also affects the quality of the recorded signal.

The task to which the present technical solution is aimed is to obtain more reliable information on the results of the analysis of the electroencephalogram when conducting electroencephalography by a non-invasive method without using an additional electrically conductive contact medium.

The problem is solved due to the fact that in a dry active electrode for a neurocomputer interface, including an electrically conductive current collector having external protrusions and a contact connector, configured to provide mechanical placement in the mating part of the contact connector, according to a utility model, the electrode contains a housing and an electronic module, the mating connector is mounted in an electronic module located in the housing and includes a protective resistor connected to the operational force elem and analog key adapted to enable receiving an external control signal.

The electronic module may be spring loaded relative to the housing, preferably by means of a shock absorbing insert made of soft elastic material and mounted between the electronic module and the wall of the housing.

The electrically conductive current collector can be made in the form of a dielectric coated with silver / silver chloride coating on its surface.

The electrically conductive current collector may be made of electrically conductive material.

The electronic module may be equipped with lead wires.

An annular protrusion is made in the housing to enable its fixing in the mounting socket of the electrode holder.

Recesses are made in the lower part of the casing to enable the extraction of the electrically conductive current collector from the mating part of the contact connector.

The housing can be made detachable.

The electronic module can be made in the form of a printed circuit board and is additionally equipped with a microcontroller and a digital potentiometer connected to it, which in turn is connected to the output of the operational amplifier and to the capacitor of the compensation circuit.

The technical result achieved by the given set of essential features is to improve the quality of the signal of electrical brain activity during electroencephalography by a non-invasive method without using an additional electroconductive contact medium by ensuring tight contact of the electroconductive current collector with the skin of a person’s head with the correct installation of the electrode and transmitting the signal to an operational amplifier to enhance signal before transferring it by wire to external devices properties.

The implementation of the electrically conductive current collector with external protrusions allows to improve the quality of the contact of the protrusions with the scalp due to the possibility of placing human hair between these protrusions, which ensures a snug fit of the contact of the electrically conductive current collector to the skin of the human head, and, therefore, improves the signal quality of electrical brain activity.

The implementation of the electrically conductive current collector removable allows you to maintain the purity of its external protrusions at any intensity of research, which affects the quality of its contact with the scalp and improves the quality of signal reception.

Supply the device with an electronic unit, where the captured signal is transmitted through the contact connector and its counterpart, mounted in the electronic module, in its pure form without distortion and interference due to the absence of wires, in order to amplify it in the electrode itself through the operational amplifier of the electronic unit before transmitting the signal via wires, provides increased signal stability to external noise during subsequent transmission to an external electronic device for further processing.

The supply of the electronic unit with an analog key made with the possibility of receiving an external control signal allows you to control the correct installation of the electrode to achieve tight contact of the electrically conductive current collector with the skin of a person’s head.

All the attributes given in the independent claim of the utility model formula are significant, since in the aggregate they affect one technical result - improving the quality of the signal of electric brain activity during electroencephalography by a non-invasive method without using an additional electrically conductive contact medium.

The essence of the claimed device is illustrated by drawings, not covering and, moreover, not limiting the scope of claims for this decision, but only being illustrative materials of a particular case of the device, where

in FIG. 1 shows a dry active electrode, a longitudinal section;

in FIG. 2 shows a dry active electrode with a shock absorbing insert, a longitudinal section;

in FIG. 3 shows the electronic unit, the principal electrical

scheme;

in FIG. 4 shows an electronic unit with a microcontroller, a circuit diagram.

The dry active electrode of the neurocomputer interface for removing electrical brain biopotentials includes an electrically conductive current collector 1, which has external protrusions 2 and a contact connector 3. Contact connector 3 is made so that it can be mechanically placed in the mate 4 of connector 3. Contact 3 and its mate made with fixation against accidental loss, for example in the form of a “button for clothes” connection. The electrode contains a housing 5 and an electronic module 6. An electronic module 6 is housed in the housing 5. The counterpart 4 of the connector 3 is mounted on the electronic module 6. The electronic module 6 includes a protective resistor 7 connected to an operational amplifier 8 and an analog key 9. Analog key 9 configured to receive an external control signal.

Between the electrically conductive current collector 1 and the rest of the circuit there is a protective resistor 7 with a nominal value of 33 kOhm or more. Its value is determined by the requirements of electrical safety (type BF according to GOST R 50267.0-92) - leakage of not more than 100 μA in case of failure. The operational amplifier 8 is included in the non-inverting amplifier circuit with a gain of +1. Its task is to transmit a signal from the point of contact of the dry electrode via a cable to an external device (for example, an electroencephalograph).

In order to further ensure a tight fit of the contact of the electrically conductive current collector 1 to the skin of a person’s head, the electronic module 6 can be spring-loaded relative to the housing, for example, by means of a shock-absorbing insert 10 (damper) made of soft elastic material and installed between the electronic module 6 and the wall of the housing 5. When In this embodiment, the electronic module 6 is guaranteed uniform clamping of the electrically conductive current collector 1 to the human skin when the electrode is in different positions on the head. The implementation of the electronic module 6 spring-loaded relative to the housing 5 allows the movement of the electronic module 6 with the inserted conductive current collector 1 to 2-3 mm inside the housing 5, which helps to reduce the stiffness of the contact of the electrode with the surface of the head and can provide a slight inclination of the replaceable part of the electrode to the surface of the head relative to housing 5.

In a preferred embodiment of the device, the electronic module 6 is made in the form of a printed circuit board.

The electrically conductive current collector 1 can be made in the form of a dielectric coated with silver / silver chloride (Ag / AgCl) or an electrically conductive material. In any case, electrical transmission of the signal from the electrically conductive current collector 1 to the connector 3 is provided.

The electronic module 6 is connected to the lead wires (not shown conventionally in the drawings), through which a supply voltage is applied, an analog output signal is transmitted to an external device, and an external electrode control signal is received. Lead wires are soldered to the electronic unit 6 and output through the hole in the housing 5.

An annular protrusion 11 is made in the housing 5 to enable its fastening on the electrode holder. In the form of an electrode holder, an elastic cap with mounting sockets made in areas corresponding to the standard lead system is most often used.

In the lower part of the housing 5, recesses 12 can be made, allowing the user to more conveniently grasp the electrically conductive current collector 1 for removing it from the mate 4 of the connector 3 when it becomes necessary to replace it.

To ensure maintainability of the device, the housing 5 can be made detachable.

To enable digital control of the device, the electronic module can be equipped with a microcontroller 13. To compensate for the intrinsic input capacitance of the electrode, a digital potentiometer 14 can be connected to the microcontroller 13, which in turn is connected to the output of the operational amplifier 8 and to the capacitor 15 of the compensation circuit. When the cable possesses a certain capacitance (usually up to several tens of pF per meter), in this case, a capacitive load compensation circuit is used in the feedback of the operational amplifier 8. Impedance measurement support is implemented using an analog switch 9 controlled by an integrated microcontroller 13.

A dry active electrode for a neurocomputer interface is used as follows.

The electrodes are mounted on the skin of a person’s head in areas of standard leads and fixed using a special electrode holder. At the same time, as a result of small circular motions made with the electrode, a large mass of hair is placed between the external protrusions 2, allowing the external protrusions 2 to come into close contact with the scalp. In the form of an electrode holder, an elastic cap with mounting sockets made in areas corresponding to the standard lead system is most often used. Using the lead wires, the electrode is connected to an external device. When assembling the wires are soldered to the electronic module 6, which fits into the housing 5, and the wires are output through the hole in the housing 5. In the initial position, the analog switch 9 is open.

The voltage of the electrode is supplied from an external device to the electronic module 6 via two wires (power and ground). Next, an assessment of the correct installation of the electrode, which occurs as follows. An analog switch 9 closes the input signal from the conductive current collector 1 to ground to provide a current return path. A small alternating voltage (up to 3 V, 10-30 Hz) is supplied through an indifferent electrode (different from the main working electrodes - it is just a wire to the current collector) through a current-measuring resistance (inside an external device). The result is a voltage divider in which the impedance of the electrode-skin contact is not known. The remaining values are known - the voltage at the contact and the supplied current. The impedance (R = U / I) of the contact is calculated from them. If the impedance (resistance) is too large (more than 100 kOhm), then the electrode has poor contact and needs to be reinstalled on the head. After checking that all the electrodes have an impedance less than the specified value, the external device turns off the key inside the electrode and enters the registration mode.

Next, the research phase begins, consisting in the removal and transmission of the signal to an external device. The signal through the scalp enters the external protrusions 2 of the electrically conductive current collector 3, then through the connector 3 through the response part 4 it enters the electronic module 6, namely, the input of the protective resistor 7. By default, the analog switch 9 is open and the signal is fed to the input of the operational amplifier 8. At the command from the outside, the analog switch 9 closes the protective resistor 7 to the ground, thus creating a return path for the measuring current. The amplified analog signal is transmitted through a wire to an external device for further processing.

When the device is operating with a microcontroller 13 built into the electronic module 6 and connected to it with a digital potentiometer 14, which in turn is connected to the output of the operational amplifier 8 and to the compensation capacitor 15 in the initial position, the microcontroller 13 is in standby mode with the clock signal turned off and not has power effects on analog circuits. Before issuing a command to the microcontroller 13, the digital control line is transferred from the outside to the logical “1” state so that the microcontroller 13 can exit the standby mode. He is then ready to receive commands on a bi-directional half-duplex digital control line. The compensation of the input capacitance of the electrode-skin contact occurs due to the capacitor 15 of the compensation circuit and is intended for the registration mode with a very large contact resistance. The contact capacitance can reach 100 pF and have a sufficiently large spread (several times), which leads to a difference in the amplitudes of the network pick-up of 50 Hz for different electrodes. After compensation, the input capacitance at the electrode is normalized and the difference in amplitudes is minimized. As a potentiometer, a digital potentiometer of 100 kOhm for 128 positions is used, controlled from the microcontroller 13. By default, the analog switch 9 is open and the signal from the electrically conductive current collector 1 is fed to the input of the operational amplifier 8. Upon a command from the outside, the key closes the protective resistor to ground, thus creating a return path for measuring current. In this way, support for measuring skin contact impedance is supported.

The use of the claimed device allows to obtain more reliable information on the results of EEG analysis during electroencephalography by a non-invasive method without using an additional electrically conductive contact medium, since it ensures the transmission of a high-quality signal and, therefore, improves the quality of its registration.

Claims (10)

1. A dry active electrode for a neurocomputer interface, comprising an electrically conductive current collector having external protrusions and a contact connector, configured to mechanically be placed in the mating part of the contact connector, characterized in that the electrode contains a housing and an electronic module, while the mating part of the contact connector is mounted into an electronic module located in the housing and including a protective resistor connected to an operational amplifier and an analog switch made with m possibility of receiving an external control signal. 2. The electrode according to claim 1, characterized in that the electronic module is spring loaded relative to the housing. 3. The electrode according to claim 2, characterized in that the electronic module is spring-loaded relative to the housing by means of a shock absorbing insert made of soft elastic material and installed between the electronic module and the wall of the housing. 4. The electrode according to claim 1, characterized in that the electrically conductive current collector is made in the form of a dielectric coated with silver / silver chloride coating on its surface. 5. The electrode according to claim 1, characterized in that the electrically conductive current collector is made of electrically conductive material. 6. The electrode according to claim 1, characterized in that the electronic module is equipped with outlet wires. 7. The electrode according to claim 1, characterized in that an annular protrusion is made in the housing to enable its fastening in the mounting socket of the electrode holder. 8. The electrode according to claim 1, characterized in that the recesses are made in the lower part of the housing to enable the extraction of the electrically conductive current collector from the mating part of the contact connector. 9. The electrode according to claim 1, characterized in that the housing is detachable. 10. The electrode according to claim 1, characterized in that the electronic module is made in the form of a printed circuit board and is additionally equipped with a microcontroller and a digital potentiometer connected to it, which in turn is connected to the output of the operational amplifier and to the capacitor of the compensation circuit.

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