JP6982304B2 - Electrodes for measuring brain activity, head-mounted devices and brain activity measuring systems using the electrodes - Google Patents

Description

The present invention relates to an electrode for measuring brain activity used for measuring brain activity, a head-mounted device using the electrode, and a brain activity measuring system.

In EEG measurement, there are wet type and dry type as a method of placing an electrode on the head of a subject. In the wet type, for example, the hair at the place where the electrode is installed is scraped off to expose the scalp, then the sebum on the scalp is removed with alcohol or the like, and the dish electrode coated with the conductive gel or the conductive paste is grounded to the scalp. .. In this case, since the contact resistance can be lowered, it is possible to acquire an electroencephalogram with less noise even with a passive electroencephalograph. However, there is a problem that sebum must be removed with alcohol, etc., and a conductive gel or conductive paste must be applied to the subject's head when measuring brain waves. It is not widely used. Further, in the passive electroencephalograph, there is a problem that the electrode wire connecting the electrode to the differential amplifier (amplifier) touches the subject or moves to become a noise source, and it is particularly difficult to measure the brain activity accompanied by the movement.
For this reason, various dry electrodes have been developed. The dry type electrode uses a metal or a conductive resin. The dry type electrode is used together with a means such as an electroencephalogram cap or a headset for fixing and grounding some kind of electrode to the subject's head, and like the wet type, a conductive gel or a conductive gel or a conductive type is used on the subject's head. It is not essential to apply the paste or remove the sebum with alcohol or the like before touching the ground. Therefore, it is expected not only for research and medical purposes but also for industrial applications such as healthcare. In the dry type electrode, the contact resistance does not decrease as compared with the case where the wet type electrode is placed by using a conductive paste or the like, so that noise derived from the environment or the like is likely to be mixed in the brain wave. Therefore, a dry electrode is usually used in combination with an active electrode in which a preamplifier is placed in the vicinity of the electrode. The active electrode preamplifier suppresses the generation of noise from the electrode line that connects the active electrode and the differential amplifier (amplifier), and even when the subject is moving, measurement of brain waves with less noise from the electrode line Will be possible. Patent Document 1 is shown as an example of such a dry type electrode. As shown in FIG. 1 and the like, Patent Document 1 is a dry type having a support portion 14 and four tilting portions 16 composed of an elastic body protruding from the surface of the support portion 14 and tilting in a specific direction. The electrode 10 for measuring brain waves, which is an electrode.

Japanese Unexamined Patent Publication No. 2017-74370

In the electroencephalogram measurement electrode 10 of Patent Document 1, the tilting portion 16 is deformed during use, and the side surface thereof comes into contact with the scalp. However, with such an electroencephalogram measurement electrode 10,
1) When the electroencephalogram measurement electrode 10 is pressed, the tilting portion 16 is deformed and the contact position shifts. That is, the position of the contact portion between the scalp and the electrode is displaced, which causes the noise of the measured brain wave.
2) Since the tilting portion 16 is deformed even after the electrode is attached, the deformation causes noise of the measured brain wave.
3) Since the tilting portion 16 may be deformed even if the subject moves a little, it is necessary to cooperate in the measurement so that the subject does not move as much as possible, which may be a heavy burden.
There are issues such as.
In view of these problems, the present invention has an electrode for measuring brain activity, which has a small noise and a small burden on the subject even when the subject is moving, a head-mounted device using the electrode, and brain activity. It provides a measurement system.

In order to solve the above problem, in the first means, in the brain activity measuring electrode used in contact with the scalp, a space is provided around the first scalp grounding portion and the first scalp grounding portion. The first scalp grounding portion and at least one of the second scalp grounding portion are provided with a plurality of arranged second scalp grounding portions, and have a function of acquiring electrical information as brain activity. The scalp grounding portion of 2 is configured to be longer than the first scalp grounding portion, and the second scalp grounding portion is made flexible.
In such a configuration, when the electrode for measuring brain activity is grounded to the scalp (head), the tip (or near the tip) of the relatively long second scalp grounding portion is first grounded to the scalp. , Can be positioned with the grounding point as the base point. Then, the electrode is pressed and the second scalp grounding portion is bent, and the first scalp grounding portion is brought close to the scalp and grounded accordingly.
The electrode for measuring brain activity may be a dry electrode capable of measuring brain activity without using a conductive paste for measuring brain waves, a conductive gel, cotton impregnated with physiological saline, or the like. Since the dry electrode does not use a conductive paste or a conductive gel, it is fixed to the head by, for example, a cap, a headset, a headgear, or the like when the electrode is grounded to the scalp. When the electrode is fixed to the head, the electrode is pressed, the second scalp grounding portion having plasticity is deformed, and the first scalp grounding portion is brought close to the scalp and grounded, so that the shape of the electrode is changed. It is fixed while being grounded to the scalp. When the electrode is grounded to a portion of the hair on the scalp, the deformation of the second plastic grounding portion of the scalp causes the hair to be scraped off.
That is, the first scalp grounding portion and the second scalp grounding portion can be firmly grounded without shifting on the scalp, and when the grounding is completed, the positions of both the first scalp grounding portion and the second scalp grounding portion are determined. The curved posture of the second scalp ground contact portion is also fixed under the pressed condition by, for example, a cap, a headset, a head gear, or the like. Therefore, even though the second scalp installation part has plasticity, the position of the electrode does not shift and the electrode itself does not deform, so that noise is less mixed in the brain activity signal and the brain activity is accurate. It is possible to obtain electrical information as.

Here, "brain activity" is generally measured as a magnetic field generated by the flow of current from the outside, a potential difference (voltage difference) at different positions, oxygenated hemoglobin, and near-infrared light amount difference due to absorption of globin etc. for deoxidization. Therefore, as the "electrode for measuring brain activity" of the present invention, for example, an electrode for measuring current for measuring current change (change in potential difference) accompanying nerve activity in the brain, or a magnetic field for changing current due to brain activity. Electroencephalogram (magnetoencephalography) measurement electrodes and changes in cerebral blood flow (oxygen cahemoglobin, deoxidized hemoglobin amount, etc.) associated with brain activity are measured as changes in the amount of near-infrared light received. It is often used as a probe for near-infrared spectroscopic measurement. In particular, when recording brain activity as a potential difference (voltage difference) (electroencephalogram measurement), a dry electrode is preferable because it can reduce the measurement burden on the subject. The brain activity may be an electroencephalogram recorded as a potential difference (voltage difference). Further, the brain activity is preferably a magnetoencephalogram recorded as a change in the magnetic field. These brain activities measure neuronal activity associated with neural activity in milliseconds, and for example, it is necessary to reduce noise contamination due to electrode misalignment or deformation.
Here, "contact with the scalp" means brain activity so that when measuring brain activity using electrodes for measuring brain activity, the brain activity can be acquired as data such as potential difference, magnetic field change, and amount of near-infrared light received. The measurement electrode is in contact with or in close proximity to the scalp. It is preferable that the electrodes for measuring brain activity are in close contact with the scalp, but they do not necessarily have to be in close contact with each other. I do not care.
The shape of the "first scalp grounding portion" and the "second scalp grounding portion" is not particularly limited. The second scalp grounding portion is plural, but the first scalp grounding portion may be one or a plurality. It is particularly good for stability that there are three or more second scalp grounding parts. The second scalp grounding portion may be grounded first with respect to the first scalp grounding portion, and may be grounded at the same time. It is necessary that at least one of the first scalp ground contact portion and the second scalp ground contact portion has a function of acquiring brain activity.
The "first scalp grounding portion" needs to have conductive performance when acquiring electrical information as brain activity. It may be a metal, but it may also be a synthetic resin material having conductive performance.
The "plurality of second scalp grounding portions" are required to have conductive performance when acquiring electrical information as brain activity. Although metal may be used, a synthetic resin material having conductive performance is particularly preferable as the material because the second scalp grounding portion has a structure having legs that bend outward. The plurality of second scalp grounding portions may all have the same shape, or may not all have the same shape. As long as they are arranged at intervals around the first scalp grounding portion, they may or may not be evenly spaced. Each does not have to be equidistant from the first scalp ground contact. The second scalp ground contact portion needs to have flexibility and elasticity to return to the original shape after bending. These definitions are the same for the following means.

Further, as a second means, the second scalp grounding portion can be bent outward.
As a result, when the plurality of second scalp ground contact portions are bent, they can be bent without interfering with each other. The second scalp ground contact portion may be configured in a curved shape so as to be convex outward in the longitudinal direction so as to be able to bend outward.

Further, as a third means, the lengths of the plurality of second scalp grounding portions are not all the same.
If the length of the second scalp grounding part is different, there is a possibility that any of the second scalp grounding parts having different lengths can touch the scalp even if the shape of the head and the amount of hair are different. Therefore, it becomes easier to acquire the brain activity signal, and the stability when the second scalp grounding portion touches the ground is increased. For example, two different lengths of the second scalp grounding portion may be prepared and arranged alternately. Alternatively, for example, a disjointed second scalp grounding portion may be prepared so as to have no rule at all.
Further, as a fourth means, one or a plurality of protrusions are formed on the back surface of the second scalp ground contact portion.
As a result, the second scalp grounding portion can ground the protruding portion other than the tip. As a result, the grounding portion is increased, so that the stability when the second scalp grounding portion is grounded is increased. Further, when the electrical information as the brain activity is acquired at the second scalp grounding portion, it becomes easy to acquire the electrical information while avoiding the hair and the like.

Further, as a fifth means, the plurality of second scalp grounding portions are arranged radially around the first scalp grounding portion.
As a result, the first scalp grounding portion is surrounded in a well-balanced manner inside the plurality of second scalp grounding portions surrounded by this, and even after the first scalp grounding portion touches the scalp, it is difficult to deviate from the grounding position. .. When the plurality of second scalp grounding portions are arranged radially, the lengths and spacings of the plurality of second scalp grounding portions may be the same or different.
Further, as a sixth means, the first scalp grounding portion and the second scalp grounding portion are extended with the main body as a base.
By having the main body, the stability of the first scalp ground contact portion and the second scalp ground contact portion is increased. Further, an amplifier circuit for amplifying the acquired brain activity signal, a circuit for filtering the brain activity signal, and the like may be built in the base of the main body.
Further, as a seventh means, the first scalp ground contact portion is configured as a plurality of protrusions.
In this way, by forming the first scalp grounding portion with a plurality of protrusions, one protrusion can be made small, the hair can be separated, and the hair is less likely to be caught between the scalp and the scalp.
In addition, even in a subject having a lot of hair, the protrusions can avoid the hair and come into contact with the scalp. The protrusions may be arranged so as to be symmetrical (line symmetry or rotational symmetry) in a plan view.

Further, as an eighth means, at least one of the first scalp grounding portion and the second scalp grounding portion is made of a synthetic resin material having conductive performance.
By constructing from a synthetic resin material with conductive performance, the subject's head does not feel cold compared to a metal material, and a soft material can be used, providing electrodes for brain activity measurement that are easy for the subject to use. can do.
Further, as a ninth means, the synthetic resin material is made to be a flexible material.
If it is made of a flexible material, the electrodes can easily adhere to the scalp and obtain electrical information such as brain potential and magnetoencephalography with as high a signal strength as possible. In addition, since the scalp grounding part bends according to the shape of the head, if there are multiple scalp grounding parts, a scalp grounding part that is not in contact or a scalp grounding part that is not in firm contact may occur. The sex becomes low. Further, even when the subject falls down, for example, the possibility of injury or damage to the scalp due to contact with the scalp is reduced.
Further, as a tenth means, the synthetic resin material contains a group of fine conductive substances so as to have conductive performance.

Here, the "synthetic resin material having conductive performance" refers to the case where the synthetic resin resin itself has conductive performance and the case where the non-conductive synthetic resin resin contains a conductive substance to have conductive performance. Includes both. When a non-conductive synthetic resin resin contains a conductive substance to have conductive performance, even if the non-conductive synthetic resin material contains a conductive substance, the non-conductive synthetic resin material May be coated with a substance containing a conductive substance. Further, when the synthetic resin material itself has conductivity, a substance containing a conductive substance may be coated. When the synthetic resin contains a conductive substance, the "fine conductive substance group" includes, for example, gold, silver, platinum, copper, nickel, aluminum, carbon black, carbon nanotube, carbon nanohorn, carbon nanobrush, and the like. Polythiophene-based, polyacetylene-based, polyaniline-based, polypyrrole-based, PEDOT / PSS and the like. Here, "fine" is at least one of fibrous and powdery forms. It may contain a conductive substance in a form other than fibrous or powdery (for example, granular or thick fibrous).
If the entire electrode is made of such a material, sufficient conductivity can be obtained even if the synthetic resin material is used as a base, and a plastic material having good moldability and low cost can be used.
The "synthetic resin material" includes thermoplastic and thermocurable plastics, synthetic rubber and / or thermoplastic elastomers, for example, styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, urethane-based thermoplastic elastomers, vinyl chloride-based heat. Plastic elastomer, polyamide-based thermoplastic elastomer, ester-based thermoplastic elastomer, polyethylene, polycarbonate, polyvinyl chloride, polypropylene, polystyrene, polylactic acid, nylon, polyacetal, modified polyphenylene ether, polyethylene terephthalate, polybutylene terephthalate, polymethylmethacrylate, polyamide , Polyurethane, polyimide, polyester, polyolefin, ABS resin, AS resin, epoxy resin, urea resin, phenol resin, melamine resin, styrene / butadiene rubber, isoprene rubber, silicone resin (silicone rubber), ethylene / propylene rubber, butyl rubber, chloroprene Refers to rubber, acrylonitrile / butadiene rubber, fluororubber, etc.
The "flexible material" is, for example, a material that is flexible and deforms when bent or pushed by receiving external pressure, but returns to its original shape by eliminating the pressure. It contains synthetic rubber, thermoplastic elastomer, or foamed plastic, for example, styrene-based thermoplastic elastomer, olefin-based thermoplastic elastomer, urethane-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, polyamide-based thermoplastic elastomer, ester-based thermoplastic elastomer. , Styrene / butadiene rubber, isoprene rubber, silicone rubber, ethylene / propylene rubber, butyl rubber, chloroprene rubber, acrylonitrile / butadiene rubber, fluororubber, flexible polyurethane foam, polyethylene foam, polystyrene foam, polypropylene foam and the like are preferable. It is not only the scalp grounding portion that is composed of the "flexible material", but the entire electrode may be composed of the flexible material.

Further, as an eleventh means, the first scalp grounding portion and the second scalp grounding portion were integrally molded as a synthetic resin molded product.
This is because if it can be integrally molded, it is advantageous in terms of cost and durability can be improved. It is better to integrally mold not only the first scalp grounding portion and the second scalp grounding portion but also the entire brain activity measuring electrode.
Further, as a twelfth means, the first scalp ground contact portion and the second scalp ground contact portion are made of different materials.
For example, the first scalp grounding portion is made of a conductive material, the second scalp grounding portion is made of a non-conductive material, or vice versa, and the first scalp grounding portion is made of a metal material, and the second The grounded part of the scalp can be made of a synthetic resin material. Further, there is a case where the first scalp ground contact portion and the second scalp ground contact portion that requires flexibility are made of materials having different flexibility and hardness. As a result, the first scalp grounding portion and the second scalp grounding portion can be made of the optimum material from the functional aspect.

Further, as a thirteenth means, electrode fixing portions are formed at the upper positions of the first scalp ground contact portion and the second scalp ground contact portion.
Further, as a fourteenth means, the electrode fixing portion was integrally molded together with the first scalp grounding portion and the second scalp grounding portion.
The electrode fixing portion is a part for fixing the electrode for measuring brain activity. As a result, the electrodes for measuring brain activity can be fixed to a base for head mounting such as a head cap or a headset by using the electrode fixing portion. If such an electrode fixing portion is integrally molded together with the first scalp grounding portion and the second scalp grounding portion, it is cost-effective.
Further, as a fifteenth means, the brain activity was recorded as an electroencephalogram.
Further, as a 16th means, the brain activity was recorded as a magnetoencephalogram.
By using such brain activity, the time resolution is high and it becomes possible to measure the brain activity in milliseconds.

Further, as the 17th means, the brain activity measuring electrode according to any one of the means 1 to 16 is attached to the head mounting base to form a head mounting device.
A specific head-mounted device equipped with the above-mentioned electrodes for measuring brain activity can hold the electrodes on the head, especially in a dry electrode that does not use paste or gel, so that the electrodes can be brought into contact with the scalp. It will be easy. In particular, it is preferable to attach it via the electrode fixing portion. Here, the "head mounting device" is a head cap having a hole at the electrode position, a headset for mounting the electrode on the head, and the like.
Further, as an eighteenth means, an amplification device for amplifying a brain activity signal was fixed to the brain activity measurement electrode.
By immediately amplifying the electroencephalogram measured by this with an amplification device, the influence of radio waves and magnetic fields from the outside is reduced, so that it is possible to acquire high-quality electroencephalograms with less external noise.
Further, as a 19th means, the amplification device was fixed to the base side, and the brain activity measuring electrode was supported by the catch portion of the amplification device.
As a result, the amplification device can be attached in advance as a member on the base side, and the electrode for measuring brain activity can be attached to such an amplification device. Therefore, only the electrode for measuring brain activity can be attached to the base side independently. Sex improves.
Further, as a twentieth means, the brain activity measuring electrode is made removable from the catch portion of the amplification device.
This makes it possible to easily fix the brain activity measuring electrode to the base side.
Further, as a 21st means, the base is sandwiched by the amplification device and a base holding portion for head mounting formed on the first scalp grounding portion and the upper part of the second scalp grounding portion. I did it.
As a result, the electrodes for measuring brain activity are firmly fixed in a predetermined position with respect to the base. It is possible to measure the brain activity of a subject simply by wearing a head-mounted device provided with electrodes for measuring brain activity that are firmly fixed in this way.

Further, as the 22nd means, the brain activity is measured based on the brain activity signal obtained by the brain activity measuring electrode of any of the 1st to 16th means.
By doing so, it is possible to reduce the time and effort required to attach the electrodes to the subject, and it is possible to provide a brain activity measurement system in which the measurement preparation time is shortened.
Further, as the 23rd means, the brain activity is measured based on the brain activity signal obtained by the head-mounted device of any of the 17th to 21st means.
By doing so, it is possible to reduce the time and effort required to attach the head-mounted device to the subject, and it is possible to provide a brain activity measurement system in which the measurement preparation time is shortened.
The inventions of the first to twenty-third means described above can be arbitrarily combined. In particular, it is preferable to include the configuration of the first means and to include at least one configuration and combination of each invention of the second to 23rd means. Any component of each invention of the first to twenty-third means may be extracted and combined with other components.

In the above invention, when the electrode for measuring brain activity is grounded to the scalp, the grounding position of both the first scalp grounding portion and the second scalp grounding portion is determined, and when the scalp is grounded, the second scalp grounding portion is used. Since the posture is determined with almost no deformation, it is possible to acquire electrical information as accurate brain activity.

The schematic explanatory view of the state which uses the brain activity measurement system in 1st Embodiment. (A) is a perspective view, (b) is a front view, and (c) is a bottom view of the electrode used in the first embodiment. In the first embodiment, (a) a partially enlarged partial cross-sectional explanatory view in a state where an electrode is attached to a cap body, and (b) is an explanatory view in a state where the electrode in (a) is grounded to the scalp. The block diagram explaining the electrical structure of 1st Embodiment. (A) is a perspective view, (b) is a front view, and (c) is a bottom view of the electrode used in the second embodiment. (A) is a perspective view, (b) is a front view, and (c) is a bottom view of the electrode used in the third embodiment. The perspective view of the electrode used in 4th Embodiment. In the electrode manufacturing process of the fourth embodiment, (a) is a front view of the first molded product, (b) is an explanatory view of a state in which the first molded product is set in a mold, and (c) is 2. Partial cross-sectional front view of the electrode molded by color molding taken out from the mold. (A) is a perspective view of the electrode used in the fifth embodiment, and (b) is a partially enlarged explanatory view of a state where the electrode is attached to the main body of the head mounting device. The schematic explanatory view of the state which uses the brain activity measurement system in 5th Embodiment.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
(First Embodiment)
As shown in FIG. 1, the electroencephalogram measurement system as the brain activity measurement system according to the first embodiment of the present invention includes a head cap set 1 as a head-mounted device and a differential amplifier 2 as a first amplification device. And the computer 3. The head cap set 1 is provided with a cap body 4 as a hemispherical base made of elastic thick cloth, and the measurer decides to measure the brain potential (voltage) reflecting the brain waves on the cap body 4. Wear it on the subject's head so that it is oriented in the correct direction. A large number of electrodes 5 for measuring brain potential (voltage) are attached to the cap body 4 (since FIG. 1 schematically shows an electroencephalogram measurement system, only some of the electrodes 5 are displayed). ..
As shown in FIGS. 2 (a) to 2 (c) and FIG. 3, the electrode 5 of the first embodiment includes a truncated cone-shaped main body 6. The main body 6 has an outer circumference that gently swells so that the meridian direction is convex outward in a quadratic curve, and the upper surface 6a and the bottom surface 6b of the main body 6 are configured to be parallel to each other in a plane. An electrode fixing portion 7 is formed on the upper surface 6a of the main body 6. The electrode fixing portion 7 is composed of a pillar portion 7a having a circular cross section and a spherical connecting portion 7b formed on the upper portion of the pillar portion 7a. The electrode fixing portion 7 serves as an energizing portion for the preamplifier 13 described later. Four protrusions 8 are formed on the bottom surface 6b of the main body 6 as a first scalp grounding portion. The protrusion 8 has a cylindrical shape with a circular cross section and protrudes downward. The protrusions 8 are arranged so as to be point-symmetrical or mirror-imaged in all directions equidistant from the center position of the bottom surface 6b. The lower end corner of the protrusion 8 is smoothly chamfered.
The first leg portion 9 and the second leg portion 10 as the second scalp ground contact portion are radially arranged and formed at a position closer to the lower side of the outer periphery of the main body 6 (also lower side toward the center in the vertical direction). The first leg portion 9 and the second leg portion 10 are arranged so that four legs are alternately extended at equal intervals from the same height position on the outer circumference of the main body 6. The first leg portion 9 and the second leg portion 10 are provided with a long first curved portion 9a and a second curved portion 10a having a circular cross section extending outward with the outer periphery of the main body 6 as a base, respectively. There is. The first curved portion 9a has the same thickness as the second curved portion 10a, but the first curved portion 9a is relatively long with respect to the second curved portion 10a. That is, the configuration is such that the second scalp grounding portions having different lengths coexist. The first curved portion 9a and the second curved portion 10a are curved so as to be convex outward, extend outward, and gently hang downward. A contact portion 11 is formed at the tips of the first curved portion 9a and the second curved portion 10a. The contact portion 11 has a spherical shape as if the tips of the first curved portion 9a and the second curved portion 10a are inflated. As shown in FIG. 2 (c), the spherical apex position of the contact portion 11 points in the downward direction. As shown in FIG. 2 (b), the contact portion 11 of the first leg portion 9 is arranged below the contact portion 11 of the second leg portion 10, and as shown in FIG. 2 (c). The contact portion 11 of the first leg portion 9 and the contact portion 11 of the second leg portion 10 are arranged so as to be equidistant from the center of the main body 6 in the bottom view.
The electrode 5 having such a shape is configured as an integrally molded product by a soft conductive material. As the material, a material appropriately selected from flexible synthetic resins can be used. In the first embodiment, as an example, a synthetic resin material (for example, polycarbonate) which is not conductive by itself is used, and carbon fibers which are conductive fibers are mixed in a dispersed manner. In the first embodiment, as an example, 30% by weight of carbon fibers having a length of about 2.0 mm is added to the synthetic resin.
In the first embodiment, the outer diameter of the electrode 5 is 14 mm, the height is 12 mm, the diameter of the circular cross section of the first and second curved portions 9a and 10a is 1.2 mm, and the contact portion is the shape before deformation. The diameter of 11 is 2.4 mm, the height of the protrusion 8 is 1.5 mm, and the diameter of the circular cross section is 1.2 mm.

The electrode 5 configured in this way is fixed to the head cap set 1 by using the electrode fixing portion 7 and the preamplifier 13 as fixing means as shown in FIG. 3A.
The preamplifier 13 as the second amplification device is made of a flexible material (for example, polyurethane foam) having a cylindrical outer shape, and an electronic substrate 13a, which is the main body of the amplification device, is housed inside. From the lower surface to the inside of the preamplifier 13, a recess 14 as a catch portion having a shape corresponding to the electrode fixing portion 7 of the electrode 5 is formed. The preamplifier 13 of each electrode 5 is connected to the differential amplifier 2 via the cable 16, and the differential amplifier 2 is connected to the computer 3 via the cable 17.
Specifically, the electrode 5 is fixed as follows. The electrode 5 is fixed by sandwiching the cloth around the mounting hole 18 of the cap main body 4 between the preamplifier 13 arranged on the outside of the cap main body 4 and the upper surface 6a of the main body 6 arranged on the inside. In the first embodiment, the electrode 5 is attached from the inside of the cap body 4. The mounting hole 18 is expanded by utilizing the elasticity of the material, and the electrode fixing portion 7 (spherical connecting portion 7b) configured to be slightly larger than the mounting hole 18 with respect to the mounting hole 10 is attached from the inside of the cap body 4. Let it pass to the outside. Then, the electrode fixing portion 7 is forcibly fitted into the recess 14 of the preamplifier 13. As a result, the fabric of the cap body 4 around the mounting hole 10 is sandwiched between the upper surface 6a of the main body 6 and the lower surface of the preamplifier 13, and the electrode 5 is fixed to the cap body 4. The electrode fixing portion 7 is freely attached to and detached from the recess 14 of the preamplifier 13.
The electrode 5 in the state of FIG. 3A fixed to the cap body 4 is pressed so as to approach the scalp when the subject wears the head cap set 1 as shown in FIG. .. Then, first, the contact portion 11 of the first leg portion 9 touches the scalp of the subject, then the second leg portion 10 contact portion 11 touches the ground, and finally the four central protrusions 8 touch the ground. With the pressing, the first curved portion 9a of the first leg portion 9 and the second curved portion 10a of the second leg portion 10 bend outward from the contact portion 11 which is in contact with the ground. Allows the protrusion 8 to touch the ground.
FIG. 3B shows a state in which the contact portion 11 of the first leg portion 9, the contact portion 11 of the second leg portion 10, and the protrusion 8 are all in contact with each other and the electrode 5 is firmly fixed on the scalp. Is.

Next, the electrical configuration of the electroencephalogram measurement system used in the first embodiment will be described with reference to FIG.
Each of the above electrodes 5 is connected to an interface 20 arranged in the differential amplifier 2 via the preamplifier 13 and the differential amplifier 2, and potential data (voltage data) is generated as brain waves acquired by the computer 3 via the interface 20. It is output.
The preamplifier 13 is attached to each of the electrodes 5 and amplifies the acquired electroencephalogram voltage at that position. The differential amplifier 2 includes a differential amplifier circuit, and calculates and amplifies an electroencephalogram voltage and a potential difference obtained from a reference electrode (not shown). Further, the differential amplifier 2 has a function of reducing noise by a built-in filter circuit. The potential data amplified by the differential amplifier 2 is output to the computer 3 as detection target data via the cable 17.
The computer 3 is composed of a CPU (central processing unit) 21, a storage device 22, and peripheral devices thereof. The CPU 21 performs arithmetic processing based on a program stored in the storage device. The storage device 22 stores basic programs such as a program for controlling the operation of the CPU 21 and an OA processing program (for example, a Japanese input function, a printing function, etc.) that manages functions that can be applied in common to a plurality of programs. ing. Further, a program for capturing potential data, a program for calculating potential difference, a program for calculating reliability of measurement data, a program for analyzing and displaying potential data, and the like are stored. An input device 23 (mouse, keyboard, etc.) and a monitor 24 are connected to the CPU 21. The monitor 24 can display the measurement results such as the obtained brain waves and differences.

With the above configuration, the following effects are obtained in the first embodiment.
(1) When the wearer wears the head cap set 1, the first leg portion 9 first touches the subject's scalp as the entire electrode 5 approaches the scalp, and then the second leg portion. The 10 is grounded, and finally the four central protrusions 8 are grounded, which is to be fixed through a plurality of stages (here, three stages). At this time, when the contact portion 11 at the tip of the first leg portion 9 and the second leg portion 10 abuts on the scalp, the electrode 5 does not deviate from the contact position as the entire electrode 5 approaches the scalp. Since the second curved portion 10a bends outward (that is, the curvature becomes large), the first curved portion 9a is fixed without shifting the position of the protrusion 8. In this way, all the parts for acquiring electrical information are firmly fixed on the scalp, which contributes to the acquisition of accurate electrical information.
(2) Because the first leg 9 first scrapes the hair and first touches the scalp, and then the adjacent second leg 10 scrapes the hair and touches the scalp with a time lag. , The number of the first leg portion 9 and the second leg portion 10 is large, and even if the first leg portion 9 and the second leg portion 10 are relatively close to each other, the hair can be easily separated. Further, the fact that the first leg portions 9 and the second leg portions 10 are alternately arranged also secures individual squeezing areas for the hair, so that the hair can be easily squeezed. Further, in this way, the cap main body 4 can be three-dimensionally supported and held in a floating state by the first leg portion 9 and the second leg portion 10, and the main body 6 is also high, so that the first and second legs can be held. Since the second legs 9 and 10 are also located below the main body 6, a space is created under the cap main body 4, so that the fabric of the cap main body 4 does not hold down the hair and maintains the function of letting the hair escape. Therefore, poor contact of the electrode with the dry electrode is less likely to occur.
(3) Since the lengths of the first leg portion 9 and the second leg portion 10 are different, it is possible to stably measure brain waves even when the shape of the head and the amount of hair are different. For example, in the case of a subject with a small face, if the legs are too long, the contact portion 11 cannot be grounded to the scalp because the curvature of the head cannot be followed. Even the subject can sufficiently follow the curvature of the head. Further, in the case of a subject having long hair, if the legs are too short, it is difficult for the contact portion 11 to scrape the hair and touch the scalp, but the long first leg 9 scrapes the hair and touches the scalp. be able to.
(4) Since the contact portion 11 at the tip of the first leg portion 9 and the second leg portion 10 is spherical, when the contact portion 11 abuts on the scalp, it always abuts on the scalp at a “point” and pinches the hair. It becomes difficult.
(5) Since the head cap set 1 is made of a thick cloth on the cap body 4, it is sufficiently heavy, so that the electrode 5 abuts on the scalp and the electroencephalogram potential can be measured just by wearing the subject. Therefore, unlike a wet electrode, it is not necessary to use a paste or the like to hold the electrode, and a simple and easy-to-use electroencephalogram measurement system can be provided.
(6) When the subject exercises, etc., because the electrodes are grounded to the scalp while being pressed by the head cap set 1 and all the parts for acquiring electrical information are firmly fixed on the scalp. However, the position of the electrode and the scalp does not shift, and the shape of the electrode itself does not change, so that brain waves with less noise can be recorded.

(Second embodiment)
The second embodiment is a variation of the electrode 5 of the first embodiment. Therefore, the detailed description of the configuration common to the first embodiment will be omitted, and the points different from the electrode 5 of the first embodiment will be mainly described. In the drawings, the members common to the electrode 5 of the first embodiment are given common numbers, and detailed description thereof will be omitted.
As shown in FIGS. 5A to 5C, the electrode 25 of the second embodiment includes a main body 6 similar to the electrode 5 of the first embodiment. An electrode fixing portion 7 similar to the electrode 5 of the first embodiment is formed on the upper surface 6a of the main body 6. The bottom surface 6b of the main body 6 is formed with four protrusions 8 similar to the protrusions 8 of the first embodiment.
The first leg portion 9 and the second leg portion 10 similar to the electrode 5 of the first embodiment are radially arranged and formed at a position closer to the lower side of the outer periphery of the main body 6.
Unlike the first embodiment, the electrode 25 of the second embodiment has a contact portion 26 having an oblong ellipsoidal shape (that is, a rugby ball shape) at the tips of the first leg portion 9 and the second leg portion 10. It is formed. The contact portion 26 has an oblong ellipsoidal outer periphery connected to the tips of the first curved portion 9a and the second curved portion 10a, and the tip direction of the contact portion 26 is the first curved portion 9a. It substantially coincides with the extending direction of the second curved portion 10a.
In the second embodiment, in the shape before deformation, the outer diameter of the electrode 25 is 16 mm, the height is 11 mm, the diameter of the circular cross section of the first and second curved portions 9a and 10a is 0.8 mm, and the contact is made. The longitudinal direction of the portion 26 is 3.0 mm, the lateral direction is 1.0 mm, the height of the protrusion 8 is 1.5 mm, and the diameter of the circular cross section is 1.2 mm.
When the electrode 25 having such a configuration is fixed to the cap body 4 in the same manner as in the first embodiment and the wearer wears the head cap set 1, the first embodiment is the same as in the first embodiment. The curved portion 9a and the second curved portion 10a of the second leg portion 10 bend outward from the contact portion 26 that has touched the ground (contact) to allow the protrusion 8 to touch the ground. In addition, the arc on the semi-major axis side of the contact portion 26 comes into contact with the ground, which is relatively along the scalp, so that the contact area increases, and the stability when the electrode 25 touches the ground is increased for accuracy. Contributes to the acquisition of electrical information.
Further, since the contact portion 26 is tapered, it is easy to separate the hair. Other effects of the first embodiment are the same in the second embodiment.

(Third embodiment)
The third embodiment is a variation of the electrode 5 of the first embodiment. Therefore, a detailed description of the configuration common to the first and second embodiments will be omitted, and the points different from the electrode 5 of the first embodiment will be mainly described. In the drawings, the members common to the electrode 5 of the first embodiment are given common numbers, and detailed description thereof will be omitted.
As shown in FIGS. 6A and 6B, the electrode 31 of the third embodiment includes a main body 6 similar to the electrode 5 of the first embodiment. An electrode fixing portion 7 similar to the electrode 5 of the first embodiment is formed on the upper surface 6a of the main body 6. Three protrusions 32 are formed on the bottom surface 6b of the main body 6. The protrusions 32 are arranged so as to be point-symmetrical or mirror-imaged on three sides equidistant from the center position of the bottom surface 6b. The lower end corner of the protrusion 32 is smoothly chamfered.
The first leg portion 33 and the second leg portion 34 as the second scalp ground contact portion are radially arranged and formed at a position closer to the lower side of the outer periphery of the main body 6. The first leg 33 and the second leg 34 are arranged so that three legs are alternately extended at equal intervals from the same height position on the outer circumference of the main body 6. The first leg portion 33 and the second leg portion 34 are provided with a long first curved portion 33a and a second curved portion 34a having a circular cross section extending outward with the outer periphery of the main body 6 as a base, respectively. There is. The first curved portion 33a has the same thickness as the second curved portion 34a, but the first curved portion 33a is relatively long with respect to the second curved portion 34a. The first curved portion 33a and the second curved portion 34a are curved so as to be convex outward, extend outward, and gently hang downward. Three small protrusions 35 are formed on the back surface (lower surface) of the first curved portion 33a and the second curved portion 34a, respectively. The small protrusions 35 are arranged in a row along the longitudinal direction of each of the first curved portions 33a or the second curved portions 34a. Each of the small protrusions 35 is formed in a truncated cone shape having the same shape, and the lower side at the tip is a bottom having a small area. The maximum diameter portion of the small protrusion 35 is smaller than the diameter of the first curved portion 33a or the second curved portion 34a. The lower end corner of the small protrusion 35 is smoothly chamfered.
In the third embodiment, in the shape before deformation, the outer diameter of the electrode 31 is 18 mm, the height is 10 mm, the diameters of the first and second curved portions 33a and 34a are circular in cross section of 1.2 mm, and the protrusion 8 is formed. The height is 1.5 mm, the diameter of the circular cross section is 1.2 mm, and the height of the small protrusion 35 is 1.5 mm.

When the electrode 31 having such a configuration is fixed to the cap body 4 as in the first embodiment and the wearer wears the head cap set 1, the first embodiment is the same as in the first embodiment. The curved portion 33a and the second curved portion 34a of the second leg portion 10 bend outward, and the small protrusion 35 comes into contact with the scalp, and then the protrusion 32 also comes into contact with the scalp. The first curved portion 33a and the second curved portion 34a themselves do not touch the scalp.
With the above configuration, in the third embodiment, the following effects are exhibited in addition to the same effects as those in the first embodiment.
(1) The small protrusions 35 formed on the first curved portion 33a and the second curved portion 34 are in contact with the scalp, respectively, and the first leg portion 33 and the second leg portion 34 are stable when they are in contact with the ground. This will increase the nature and contribute to the acquisition of accurate electrical information.
(2) The first leg 33 and the second leg 34 have a small protrusion 35 having a maximum diameter smaller than the diameter of the first leg 33 and the second leg 34 having a deflated tip. Therefore, they make it easier to separate the hair.

(Fourth Embodiment)
The fourth embodiment is a variation of the electrode 5 of the first embodiment. Therefore, the detailed description of the configuration common to the first embodiment will be omitted, and the points different from the electrode 5 of the first embodiment will be mainly described. In the drawings, the members common to the electrode 5 of the first embodiment are given common numbers, and detailed description thereof will be omitted.
As shown in FIGS. 7 and 8 (a) to 8 (c), the electrode 36 of the fourth embodiment has exactly the same external shape as the electrode 5 of the first embodiment. However, the electrode 36 is different from the electrode 5 of the first embodiment in that different materials are combined to form one electrode 36. The electrode 36 is composed of two types of synthetic resins by two-color molding. The electrode 36 is formed by the following procedure.
First, as shown in FIG. 8A, the first molded product 37 is molded. The first molded product 37 is molded with a mold (not shown). The first molded product 37 has a part of the main body 6 and a portion to be an electrode fixing portion 7 and a protrusion 8 in the future.
As shown in FIG. 8B, the first molded product 37 is arranged in the mold 38. A cavity 39 having a shape as shown by a broken line is formed around the first molded product 37 of the mold 38. A second molded product, that is, an electrode 36 is molded so as to surround the first molded product 37 by filling the cavity 39 with a molten resin and releasing the mold from the mold 38 after solidification (FIG. 8 (FIG. 8). c) State).
In the electrode 36, both the first molded product 37 and the second molded product 40 are made of a soft material. In the present embodiment, since electrical information is acquired from the protrusion 8 on the first molded product 37 side and the preamplifier 13 is energized from the electrode fixing portion 7, the first molded product 37 side is made conductive. On the other hand, the second molded product 40 is non-conductive. Thermoplastic plastic (for example, polycarbonate) is used as an example of the first molded product 37, and carbon fibers, which are conductive fibers, are mixed in a dispersed manner. In the fourth embodiment, as an example, 30% by weight of carbon fibers having a length of about 2.0 mm is added to the synthetic resin. On the other hand, the second molded product 40 is made of a thermosetting synthetic resin (for example, a silicone resin) as an example.
Such an electrode 36 is worn and used in the head cap set 1 in the same manner as the electrode 5 of the first embodiment.
With such a configuration, the following effects are exhibited in addition to the same effects as those in the first embodiment.
(1) The protrusion 8 is surrounded by the first leg portion 9 and the second leg portion 10, and unlike the above embodiment, only the protrusion 8 is responsible for acquiring electrical information. Therefore, for example, the subject Even if the posture is changed and the first leg portion 9 and the second leg portion 10 are slightly deformed, they are not affected by the deformation. That is, in the fourth embodiment, the first leg portion 9 and the second leg portion 10 play a role of surrounding the protrusion 8 and reliably holding the position of the protrusion 8 without acquiring electrical information. Therefore, it is possible to acquire more accurate electrical information.
(2) In the fourth embodiment, since the materials of the protrusion 8, the first leg 9, and the second leg 10 are different, the first leg 9 and the second leg 10 that come into contact with the scalp It is possible to use the optimum material for the hardness and the degree of bending of the first leg portion 9 and the second leg portion 10 regardless of the protrusion 8.

(Fifth Embodiment)
The fifth embodiment is another variation different from the electrodes of each of the above embodiments.
The electrode 41 of the fifth embodiment is an example of being mounted on a head cap set 51 as a head mounting device different from the first to fourth embodiments. First, the electrode 41 will be described.
As shown in FIGS. 9A and 9B, the electrode 41 includes a columnar main body 42. The main body 42 has a flange portion 43 having a diameter slightly larger than the diameter of the main body 42 formed in the center in the longitudinal direction. A male screw portion 42a is formed on the outer periphery on the upper side of the main body 42 with the flange portion 43 as a boundary. The bottom surface of the main body 42 is a grounding portion 45 as a first scalp grounding portion. The corners that intersect the main body 42 around the ground contact portion 45 are smoothly chamfered. A leg portion 46 as a second scalp grounding portion is formed on the lower outer periphery of the flange portion 43 of the main body 42. The three legs 46 are arranged radially. Each leg 46 includes a long curved portion 47 having a circular cross section. The curved portion 47 is curved so as to be convex outward, extends outward, and gently hangs downward. Similar to the electrode 5 of the first embodiment, the contact portion 48 is formed at the tip of the curved portion 47. The contact portion 48 has a spherical shape as if the tip of the curved portion 47 is inflated. As shown in FIG. 9B, the spherical apex position of the contact portion 48 points in the downward direction.
In the fifth embodiment, the shape before deformation is such that the outer diameter of the electrode 41 is 8 mm, the height is 12 mm, the diameter of the circular cross section of the curved portion 47 is 0.8 mm, and the diameter of the contact portion is 1.5 mm. Has been done.

Next, the head cap set 51 on which the electrodes 41 are mounted and the electroencephalogram measurement system will be described. As shown in FIG. 10, the electroencephalogram measuring system according to the fifth embodiment of the present invention includes a head cap set 51 and a computer 52. The head cap set 51 includes a cap body 53 as a base made of a lightweight and rigid plastic frame. A large number of electrodes 41 are arranged on the inner surface of the cap body 53. However, in FIG. 10, since the electroencephalogram measurement system is schematically shown, only a part of the electrodes 41 are displayed. A differential amplifier 54 as a first amplification device is housed on the inner surface of the cap body 53. Similar to the first embodiment, the potential data amplified by the differential amplifier 54 is output to the computer 52 as detection target data via the cable 55. The subject attaches the cap body 53 to the subject's own head so as to have a predetermined orientation for measuring the brain potential (voltage) reflecting the brain wave.

Such an electrode 41 is fixed to the cap body 53 by the preamplifier 49 and the flange portion 43. The preamplifier 49 has a disk-shaped thin plate-like appearance, and a female screw portion 49a as a catch portion that can be screwed with the screw of the male screw portion 42a of the main body 42 is formed in the central through hole. The preamplifier 49 is arranged on the mounting hole 18 of the cap main body 53, the male screw portion 42a of the main body 42 is inserted outward from the inside of the cap main body 53, and the male screw portion 42a is inserted into the preamplifier 49 on the upper side (inside) of the cap main body 53. Screw and fasten with the female screw portion 49a of. As shown in FIG. 9B, the cap body 53 is sandwiched between the preamplifier 49 and the flange portion 43 in a firmly fastened state, and the electrode 41 is fixed to the cap body 53. From such a fastened state, the male screw portion 42a can be removed from the cap body 53 of the electrode 41 by rotating the male screw portion 42a in the opposite direction to the female screw portion 49a.
When the electrode 41 having such a configuration is fixed to the cap body 53 and the wearer wears the head cap set 51, the contact portion 48 is grounded and the curved portion is grounded as in the first embodiment. It bends outward from the (contacted) contact portion 48 as a base point, and allows the ground contact portion 45 to touch the scalp.
With such a configuration, the following effects are exhibited in addition to the same effects as those in the first embodiment.
(1) Since the outer diameter of the electrode 41 can be designed to be small, the electrode can be grounded at a more accurate position and brain information can be acquired from a more limited part.
(2) Since the electrode 41 has a simple structure, it is possible to reduce the cost of manufacturing a prototype, a mold, and the like.

The above-described embodiment is merely described as a specific embodiment for exemplifying the principle of the present invention and its concept. That is, the present invention is not limited to the above embodiment. The present invention can also be embodied in a modified manner as follows, for example.
The form and size of each of the electrodes 5, 25, 31, 36, 41 of the first to fifth embodiments is an example, and it is free to carry out in other forms.
For example, in the first to fourth embodiments, the first leg portion 9 and the second leg portion 10 (the first leg portion 33 and the second leg portion 34) having different lengths are used. The second scalp ground contact portion may be configured with the same length, or conversely, the second scalp ground contact portion having three or more different lengths may be formed.
-In the above embodiment, carbon fiber is mixed with the synthetic resin material as conductive fine particles in order to have conductivity. However, the present invention can be realized without mixing such conductive fine particles with the material itself.
-The above is an example of the material constituting each electrode 5, 25, 31, 36, 41, and other synthetic resin materials can be freely used. By changing the material, it is possible to change various properties such as flexibility, elasticity, and curability.
For example, the electrode may be made of a material in which the synthetic resin material itself has conductivity. Alternatively, a conductive coat layer may be formed on the outer surface of the electrode. When forming such a coat layer, it is preferable to mix a group of conductive substances such as conductive fibers, powders, and granules with the coating agent to develop conductivity. The coat layer may be formed by coating or a dip method, but may be formed by other means.
-The electrode 36 of the fourth embodiment was composed of two types of synthetic resins by two-color molding. However, the first molded product 37 may be made of a conductive metal material instead of a synthetic resin material. That is, the electrode 36 of the fourth embodiment may be formed by insert molding in which a metal is inserted and a synthetic resin is arranged around the metal.
-In each of the above embodiments, the electrodes 5, 25, 31, 36, 41 are fixed to the cloth cap body 4, but for example, a head cap in which the electrodes are attached to a non-cloth plastic frame. It may be a set.

-In the third embodiment, the small protrusions 35 are formed three by three in a row along the longitudinal direction of the first curved portion 33a or the second curved portion 34a. However, the number of small protrusions may be one, four or more, and may be formed in two or more rows. Also, the shapes of the small protrusions do not have to be the same.
-In the fourth embodiment, the protrusion 8 on the side of the first scalp ground contact portion is made of a conductive material, and the first leg portion 9 and the second leg portion 10 serving as the second scalp ground contact portion are formed. Was composed of a non-conductive material, but this relationship may be reversed. In this case, it is preferable that the electrode fixing portion 7 secures conductivity as a molded product on the second molded product 40 side. Since the first leg portion 9 and the second leg portion 10 will not be deformed when the protrusion 8 is in contact with the scalp, even if the protrusion 8 is specialized for positioning rather than acquiring the electrical upper part. good.
-It is not always necessary to use a preamplifier when fixing each of the electrodes 5, 25, 31, 36, 41. The electrodes 5, 25, 31, 36, 41 may be fixed by means other than the preamplifier. For example, when the cap body is provided with a member that engages with the electrode fixing portions formed on the electrodes 5, 25, 31, 36, 41 separately from the preamplifier, and the preamplifier does not have the function of fixing the electrodes. There may be.
-As the catch portion, in the above, the electrode fixing portion 7 is attached to and detached from the concave portion 14 of the preamplifier 13, and the male screw portion 42a on the electrode side is fixed by screwing the female screw portion 49a on the preamplifier 49 side. However, these are examples, and the electrodes 5, 25, 31, 36, 41 may be fixed to the base side by other means.
-The interface 20 connecting the differential amplifier and the computer has been described as an example of being connected by wire in the above embodiment, but may be communication by wireless or the like. Further, the information transmission between the preamplifier and the differential amplifier is not limited to wired communication, and the use of wireless communication or the like is also included in the variation of the present invention.
The invention of the present application is not limited to the configuration described in the above-described embodiment. The components of each of the above-described embodiments and modifications may be arbitrarily selected and combined. Further, any component of each embodiment or modification, and any component described in the means for solving the invention or any component described in the means for solving the invention are embodied. It may be configured in any combination with. We also intend to acquire the rights to these in the amendment or divisional application of the present application.
In addition, he intends to acquire the rights to the whole design or the partial design by filing a change application to a design application. Although the entire drawing of the device is drawn with a solid line, it is a drawing including not only the whole design but also the partial design requested for a part of the device. For example, it is a drawing which includes a part of the device as a partial design regardless of the member as well as a part of the member of the device as a partial design. The part of the device may be a part of the device or a part of the member.

5, 25, 31, 36, 41 ... Electrodes, 8, 32 ... Protrusions as the first scalp ground contact portion, 9, 33 ... First leg portion as the first scalp ground contact portion 10, 34 ... Second The second leg as the scalp grounding part.

Claims (23)

In the electrode for measuring brain activity used in contact with the scalp,
A first of the scalp grounding portion, and a plurality of second scalp grounding portions arranged at intervals around the same first scalp grounding portion, the first scalp ground unit and the second scalp At least one of the grounding portions has a function of acquiring electrical information as brain activity, and the second scalp grounding portion radially arranged around the first scalp grounding portion is the first scalp. For brain activity measurement, the second scalp ground contact portion is longer than the ground contact portion, two types having different lengths are alternately arranged, and the second scalp ground contact portion has flexibility. electrode. The electrode for measuring brain activity according to claim 1, wherein the second scalp grounding portion can be bent outward. The electrode for measuring brain activity according to claim 1 or 2, wherein the tip of the second scalp grounding portion has a spherical contact portion. The second brain activity measuring electrode according to 1 or 2, characterized in Rukoto which having a contact portion of the Chohei ellipsoidal to the tip of the scalp ground portion. The electrode for measuring brain activity according to any one of claims 1 to 4, wherein one or a plurality of protrusions are formed on the back surface of the second scalp grounding portion. The electrode for measuring brain activity according to any one of claims 1 to 5, wherein the first scalp grounding portion and the second scalp grounding portion extend from the main body as a base. The electrode for measuring brain activity according to any one of claims 1 to 6, wherein the first scalp grounding portion is configured as a plurality of protrusions. The brain activity measurement according to any one of claims 1 to 7, wherein at least one of the first scalp grounding portion and the second scalp grounding portion is made of a synthetic resin material having conductive performance. Electrode for. The electrode for measuring brain activity according to claim 8, wherein the synthetic resin material is a flexible material. The electrode for measuring brain activity according to claim 8 or 9, wherein the synthetic resin material contains a group of fine conductive substances to have conductive performance. The electrode for measuring brain activity according to any one of claims 1 to 10, wherein the first scalp grounding portion and the second scalp grounding portion are integrally molded as a synthetic resin molded product. The electrode for measuring brain activity according to any one of claims 1 to 11, wherein the first scalp grounding portion and the second scalp grounding portion are made of different materials. The electrode for measuring brain activity according to any one of claims 1 to 12, wherein an electrode fixing portion is formed at an upper position of the first scalp grounding portion and the second scalp grounding portion. The electrode for measuring brain activity according to claim 13, wherein the electrode fixing portion is integrally molded together with the first scalp ground contact portion and the second scalp ground contact portion. The electrode for measuring brain activity according to any one of claims 1 to 14, wherein the brain activity is recorded as an electroencephalogram. The electrode for measuring brain activity according to any one of claims 1 to 14, wherein the brain activity is recorded as a brain magnetic field. A head-mounted device in which the brain activity measuring electrode according to any one of claims 1 to 16 is attached to a head-mounted base. The head-mounted device according to claim 17, wherein an amplification device for amplifying a brain activity signal is fixed to the brain activity measurement electrode. The head-mounted device according to claim 18, wherein the amplification device is fixed to the base side, and the brain activity measuring electrode is supported by a catch portion of the amplification device. The head-mounted device according to claim 19, wherein the brain activity measuring electrode is removable from the catch portion of the amplification device. 17. Claim 17, the base is sandwiched between the amplification device and a head-mounting base holding portion formed on the first scalp grounding portion and the upper portion of the second scalp grounding portion. The head-mounted device according to any one of 20 to 20. A brain activity measuring system that measures brain activity based on a brain activity signal obtained by the brain activity measuring electrode according to any one of claims 1 to 16. A brain activity measuring system that measures brain activity based on a brain activity signal obtained by the head-mounted device according to any one of claims 17 to 21.

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