Brain function measuring device and brain function measuring method

Abstract

To non-invasively but correctly measure the active section and active situation of the brain by a comparatively simple device configuration.SOLUTION: Magnetic field generating means (2) is disposed on a scalp (1) of a subject (P) and generates a magnetic field that emanates from the north pole, passes through a cerebral cortex (3) of the subject (P) and returns to the south pole in a loop path. Magnetic field detecting means (5) is disposed on the scalp (1) and detects a change in the magnetic field (4) as a signal reflecting an activity status of the brain.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a brain function measuring device and a brain function measuring method that include a magnetic field generating means, such as a magnet, that generates a magnetic field that returns from a north pole to a south pole via a loop-shaped path, and a magnetic field detecting means that detects changes in the magnetic field. [Background technology]

[0002] In recent years, functional near-infrared spectroscopy (NIRS) has been proposed as a method for measuring brain function non-invasively. This method uses near-infrared light to measure the information transmission function of nerve cells when visual and auditory information taken in by sensory organs such as the eyes and ears is converted into an electrical signal and transmitted to the brain, as a change in the amount of oxygenated hemoglobin flowing through the capillaries in the brain.

[0003] Patent Documents 1 and 2 disclose a non-invasive brain function measuring device that uses functional near-infrared spectroscopy to measure brain activity in the cerebral cortex. This measuring device irradiates the brain with near-infrared light from a light source placed on the subject's scalp (hereinafter sometimes abbreviated as scalp), and receives reflected light and scattered light generated by this irradiation with a light receiver also placed on the scalp, thereby measuring the brain activity state as a change in blood flow in the brain's capillaries.

[0004] In addition, the invention of Patent Document 3 discloses a non-invasive brain function measurement method by measuring near-infrared light transmitted through the brain, in which a near-infrared light source is placed in the oral cavity, near-infrared light is irradiated from the base of the brain toward the scalp, and the transmitted light is received by a light receiver placed on the scalp, thereby measuring the brain activity as a change in blood flow in the brain's capillaries. In this case, since the near-infrared light transmits deep inside the brain, it is possible to measure brain function reflecting the activity inside the brain.

[0005] Furthermore, the invention in Patent Document 4 is disclosed as a non-invasive brain function measuring device using magnets or the like, in which a magnetic field source such as a magnet is placed inside the mouth, a magnetic field is generated from the base of the brain toward the scalp, and the transmitted magnetic field is measured by a magnetic field detector placed on the scalp, thereby measuring brain activity as changes in the magnetic field. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 57-115232 [Patent Document 2] Japanese Patent Application Publication No. 63-275323 [Patent Document 3] JP 2010-082370 A [Patent Document 4] JP 2018-122019 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the measuring devices disclosed in the above Patent Documents 1 and 2, the light source of near-infrared light is located on the same scalp as the light receiver that receives the reflected and scattered light, so the light source and the light receiver must be spaced apart, for example, by several centimeters. This results in low spatial resolution, and only brain activity in shallow parts of the brain can be measured, making it impossible to measure brain functions inside the brain with high accuracy. In addition, the change in absorbance of oxygenated hemoglobin and deoxygenated hemoglobin can only be measured on the order of a few seconds at most, and the temporal resolution is also low.

[0008] In the brain function measuring device disclosed in Patent Document 3, since a light source for emitting near-infrared light is placed in the oral cavity, power must be supplied to the light source, for example, by drawing a lead wire or a signal wire into the oral cavity or placing a battery in the oral cavity. This causes discomfort to the subject and makes the measurement work complicated. In addition, since the near-infrared light passes through the base of the brain, there is a concern that the near-infrared light may adversely affect the sensory organs close to the base of the brain, such as the retina of the eye. Furthermore, the light receiver must be placed in close contact with the scalp, and if hair or the like is caught between the light receiver and the scalp, the measurement sensitivity decreases.

[0009] In the brain function measuring device disclosed in Patent Document 4, a magnetic field source such as a magnet is placed in the oral cavity, a magnetic field is generated from the base of the brain in the direction of the scalp, and the transmitted magnetic field is measured by a magnetic field detector placed on the scalp. In this way, some of the problems of the brain function measuring device disclosed in Patent Document 3 are solved. However, as is well known, the static magnetic field from a magnet or the like returns in a loop-shaped path from the north pole to the south pole, which causes a deviation between the active area of ​​the brain and the measurement point on the scalp, making it difficult to identify the cerebral cortex near the straight line connecting the magnet and the magnetic field detector as the active area.

[0010] In view of the above problems, the present invention aims to provide a brain function measuring device and a brain function measuring method that enable high-precision measurement that can accurately and easily identify active areas of the brain. More specifically, the present invention aims to provide a brain function measuring device and a brain function measuring method that irradiate a static magnetic field from a magnet placed on the scalp to the inside of the scalp, utilize the phenomenon in which the static magnetic field from the magnet returns along a loop-shaped path, and measure the strength of the magnetic field that returns to the scalp via the cerebral cortex at the outermost part of the brain with a magnetic field detector, thereby measuring the active areas and activity state of the brain. [Means for solving the problem]

[0011] In order to achieve the above object, a brain function measuring device according to a first aspect of the present invention comprises: A magnetic field generating means is placed on the scalp of a subject, and generates a magnetic field that emanates from the N pole, passes through the cerebral cortex of the subject, and returns to the S pole via a loop-shaped path; a magnetic field detection means arranged on the scalp and configured to detect a change in the magnetic field as a signal reflecting an activity state of the cerebral cortex; Equipped with.

[0012] The magnetic field generating means is a permanent magnet such as a ferrite magnet, a samarium-cobalt magnet, an alnico magnet, or a neodymium magnet, or an electromagnet. It may also be possible to do so.

[0013] The magnetic field detection means is any one of a one-axis magnetic field detector, a two-axis magnetic field detector, and a three-axis magnetic field detector. It may also be possible to do so.

[0014] The magnetic field generating means and the magnetic field detecting means are housed in a magnetic shielding container that blocks magnetic fields from the outside world that enter from a portion other than the portion facing the scalp. It may also be possible to do so. That is, the magnetic field generating means and the magnetic field detecting means are installed as a measurement set (hereinafter sometimes abbreviated as a detection end) in a magnetic shielding container to avoid interference with other magnetic field generating means or magnetic fields such as geomagnetism present in the measurement environment. It may also be possible to do so.

[0015] A rotating member is provided to which the magnetic field generating means and the magnetic field detecting means are attached, and the rotating member is configured to rotate freely by rotating an axis perpendicular to the scalp, with the center of rotation being the center of a line connecting the magnetic field generating means and the magnetic field detecting means. It may also be possible to do so.

[0016] The magnetic field generating means has a structure that allows the pole facing the scalp to be changed to either an N pole or an S pole. It may also be possible to do so.

[0017] In order to achieve the above object, a brain function measuring method according to a second aspect of the present invention comprises: A brain function measuring method for non-invasively measuring brain function, comprising: A magnetic field is applied to the cerebral cortex, which is the outermost part of the brain of the subject, using a magnetic field generating means placed on the scalp of the subject; Due to the phenomenon in which the static magnetic field from the magnetic field generating means originates from the north pole, passes through the cerebral cortex, and returns to the south pole via a looped path, the returning magnetic field is detected by a magnetic field detection means placed on the scalp as a signal reflecting the activity state of the cerebral cortex.

[0018] As the magnetic field generating means, for example, a permanent magnet or an electromagnet such as a ferrite magnet, a samarium-cobalt magnet, an alnico magnet, or a neodymium magnet is used. It may also be possible to do so.

[0019] The magnetic field detection means is a one-axis magnetic field detector, a two-axis magnetic field detector, or a three-axis magnetic field detector. It may also be possible to do so.

[0020] A magnetic shielding container that houses the magnetic field generating means and the magnetic field detecting means is used to block magnetic fields from the outside that enter from areas other than the area facing the scalp. It may also be possible to do so. In other words, the magnetic field generating means and the magnetic field detecting means can be used as a measurement set (hereinafter sometimes abbreviated as the detecting end) by being installed in a magnetically shielded container to avoid interference with other magnetic field generating means or magnetic fields such as the earth's magnetic field present in the measurement environment.

[0021] The magnetic field generating means and the magnetic field detecting means are attached, and a rotating member having an axis perpendicular to the scalp is rotated around the center of a line connecting the magnetic field generating means and the magnetic field detecting means, thereby changing the relative relationship between the direction in which the magnetic field is irradiated and the direction of the nerve fibers in the cerebral cortex, thereby generating a magnetic field with the magnetic field generating means and detecting the magnetic field with the magnetic field detecting means. It may also be possible to do so.

[0022] The direction of the magnetic field irradiated to the cerebral cortex is changed by selecting the pole facing the scalp as an N pole or an S pole in the magnetic field generating means, and the magnetic field is detected by the magnetic field detecting means. It may also be possible to do so. Effect of the Invention

[0023] According to the brain function measuring device and the brain function measuring method of the present invention, the activation state of nerve cells in the cerebral cortex can be measured non-invasively with a relatively simple device configuration, and by using a magnetic field signal, it is possible to perform highly accurate measurement without being affected by hair or the like that is caught between the detection end and the scalp. In addition, by configuring the detection end to be freely rotatable, the direction of the irradiated magnetic field can be changed by simply attaching the detection end, and information regarding the direction of nerve fibers in the cerebral cortex can be obtained in a simple procedure. [Brief description of the drawings]

[0024] [Figure 1] 1 is a schematic diagram showing a configuration of a brain function measuring device of the present invention. [Diagram 2] FIG. 1 is a schematic diagram showing a configuration of a brain function measuring device equipped with a magnetic shielding container. [Figure 3A] FIG. 13 is a diagram showing the concept of measurement when the polarity of the magnetic field generating means is changed, in which the surface in contact with the scalp is the N pole. [Figure 3B] FIG. 13 is a diagram showing the concept of measurement when the polarity of the magnetic field generating means is changed, in which the surface in contact with the scalp is the S pole. [Figure 3C] FIG. 13 is a diagram showing an example of a structure in which the pole facing the scalp can be arbitrarily changed to either the N pole or the S pole. [Figure 4A] FIG. 13 is a schematic diagram showing an example of a detection end having a rotatable function. [Figure 4B] FIG. 4 is a partial cross-sectional view of an attachment board and a magnetic shield container. [Figure 4C] FIG. 2 is a schematic diagram showing the positional relationship of components of the brain function measuring device. [Diagram 5] FIG. 1 is a schematic diagram showing the flow of a brain function measuring method. [Figure 6A] FIG. 1 is a schematic diagram showing a measurement image according to a conventional method. [Figure 6B] FIG. 2 is a schematic diagram showing a measurement image of the brain function measuring device of FIG. 1. [Figure 7] FIG. 1 is a diagram showing an example of the appearance of a brain function measuring apparatus. [Figure 8A] This figure shows the brain function measurement method and measurement results when stimulating the median nerve at the right wrist, and shows the arrangement of 16 detection terminals on the scalp. [Figure 8B] 1 is a graph showing time-series signals measured at each detection end. [Figure 9] 11 is a graph showing a difference in detection results when the direction of a magnetic field is changed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The present invention is a brain function measuring device and a brain function measuring method that use a magnetic field to measure the brain's activation state. The present invention has the following advantages over electroencephalography (EEG) in solving the inverse problem of evaluating which part of the subject's brain is activated based on the measurement results at multiple points on the subject's scalp. 1. The magnetic permeability of the head is nearly uniform, enabling more accurate measurements than EEG methods, which are easily affected by differences in the dielectric constant of the materials between the nerve cells and the scalp (cerebrospinal fluid, dura mater, bone, etc., hereafter sometimes abbreviated as intervening materials). 2. Since the effect of the intervening material does not need to be taken into account when solving the inverse problem, the algorithm can be simplified.

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, components having the same functions are designated by the same reference numerals, and the description thereof may be omitted.

[0027] 1 shows the configuration of a brain function measuring apparatus 100 according to the present embodiment. As shown in FIG 1, the brain function measuring apparatus 100 includes a magnetic field generating means 2 and a magnetic field detecting means 5.

[0028] The magnetic field generating means 2 is disposed on the upper part of the scalp 1 of the subject P. The magnetic field generating means 2 irradiates a magnetic field (static magnetic field) 4 to the cerebral cortex 3, which is the subject of measurement of the brain activity state of the subject P. The magnetic field 4 emanates from the north pole, passes through the cerebral cortex 3 of the subject P, and returns to the south pole via a looped path. In this embodiment, the direction of irradiation of the magnetic field is the direction in which the north pole is seen from the south pole in the magnetic field generating means 2. The magnetic field generating means 2 is a permanent magnet, but may also be an electromagnet. When a permanent magnet is used, a ferrite magnet, a samarium-cobalt magnet, an alnico magnet, or a neodymium magnet can be adopted. When an electromagnet is used, an electromagnetic coil can be adopted.

[0029] The magnetic field detection means 5 detects changes in the magnetic field 4 that has returned to the scalp 1 after being altered by interaction with brain activity. The activity state of the cerebral cortex 3 is measured based on the detection result of the magnetic field detection means 5. The magnetic field detection means 5 may be a 1-axis magnetic field detector that detects a magnetic field in one axis direction, a 2-axis magnetic field detector that detects a magnetic field in two orthogonal axes, or a 3-axis magnetic field detector that detects a magnetic field in three orthogonal axes.

[0030] The signal indicating the activity state of the cerebral cortex 3 detected by the magnetic field detection means 5 is converted into time-series digital signal data by an analog / digital converter 10. The converted digital signal data is stored in a device 11 consisting of a personal computer or the like. The digital signal data stored in the device 11 is subjected to signal processing, calculations, etc. as necessary.

[0031] 1 shows only one set of magnetic field generating means 2 and magnetic field detecting means 5 and their measurement state. However, if multiple sets of magnetic field generating means 2 and magnetic field detecting means 5 are placed at each measurement point on the upper part of the scalp 1 of the subject P as necessary, it becomes possible to simultaneously measure the activity state of the cerebral cortex 3 at each of the multiple measurement points.

[0032] 2, 3A, 3B, and 4A, the brain function measuring apparatus 100 further includes a magnetic shield container 6 and an attachment board 7. The magnetic shield container 6 is a hollow cylindrical container, and is disposed so that a bottom surface portion 6a faces the scalp 1. The attachment board 7 is disposed on the scalp 1 and supports the magnetic shield container 6.

[0033] The magnetic shielding container 6 is made of a material that blocks magnetism, except for the bottom surface 6a. This is to avoid interference with other magnetic field generating means 2 or magnetic fields such as geomagnetism present in the measurement environment. The magnetic field generating means 2 and the magnetic field detecting means 5 are housed in the magnetic shielding container 6, and specifically, are arranged near the bottom surface 6a. The bottom surface 6a on which the magnetic field generating means 2 and the magnetic field detecting means 5 are arranged is also referred to as the detection end.

[0034] The bottom surface 6a of the magnetic shielding container 6 is made of a material that does not have a magnetic shielding effect in order to enable irradiation of a magnetic field by the magnetic field generating means 2 and detection of the magnetic field by the magnetic field detecting means 5. In this way, by covering the magnetic field generating means 2 and the magnetic field detecting means 5 with the magnetic shielding container 6 that blocks magnetic fields from the outside that enter from areas other than the area facing the scalp 1, it becomes possible to perform highly accurate measurements while suppressing the influence of magnetic fields that become noise.

[0035] In order for the magnetic field detection means 5 to detect the magnetic field 4 that emanates from the N pole of the magnetic field generation means 2 and passes through the cerebral cortex 3, the magnetic field generation means 2 and the magnetic field detection means 5 must be installed at a predetermined distance. As shown in FIG. 2, in this embodiment, the distance between the magnetic field generation means 2 and the magnetic field detection means 5 is 25 mm. However, the present invention is not limited to this. This distance need only be such that the magnetic field that emanates from the N pole of the magnetic field generation means 2 and passes through the cerebral cortex 3 can be adequately detected by the magnetic field detection means 5, and is not limited to 25 mm.

[0036] 3A and 3B show the structure of the detection end 6a in which the polarity of the magnetic field 4 irradiated from the magnetic field generating means 2 to the cerebral cortex 3 is changed. In FIG. 3A, the side in contact with the scalp 1 is the magnetic pole N, and in FIG. 3B, the side in contact with the scalp 1 is the magnetic pole S. The interaction between the magnetic field 4 and the activity of the cerebral cortex 3 changes depending on their relative directions. Therefore, as shown in FIG. 3A and FIG. 3B, by changing the direction of the magnetic field as necessary, it becomes possible to perform measurement corresponding to the direction of activity of the nerve fibers in the cerebral cortex 3. Note that when the magnetic field generating means 2 is an electromagnet (electromagnetic coil), the N pole and S pole can be reversed by reversing the current flowing through the electromagnetic coil.

[0037] The magnetic field generating means 2 and the magnetic field detecting means 5 are placed on the bottom surface 6a of the magnetic shielding container 6, and the magnetic field generating means 2 is rotated manually or, as shown in FIG. 3C, by a rotary driving means 2a such as a motor. In this way, the direction of the magnetic field 4 irradiated to the cerebral cortex 3 having a complex structure can be changed. As a result, it becomes possible to easily detect a detection signal by the magnetic field detecting means 5 when the relative direction of the magnetic field 4 and the nerve cells is changed, while keeping the detection end 6a placed on the scalp 1. The magnetic field generating means 2 has a structure that allows the pole facing the scalp 1 to be arbitrarily changed to a north pole or a south pole.

[0038] As shown in FIG. 4A, the magnetic shield container 6 and the mounting plate 7 are configured to be slidable in order to allow the magnetic shield container 6 to rotate freely. Specifically, the mounting plate 7 is provided with an axis 7a perpendicular to the scalp 1. As shown in FIG. 4B, the axis is inserted into a through hole 6b provided in the center of the bottom surface 6a of the magnetic shield container 6 as a rotating member. With this configuration, the magnetic shield container 6 is supported to be rotatable around the axis 7a of the mounting plate 7. The magnetic field generating means 2 and the magnetic field detecting means 5 are attached to the inner side surface of the magnetic shield container 6. With this configuration, as shown in FIG. 4C, the axis 7a of the mounting plate 7 is the center of the line connecting the magnetic field generating means 2 and the magnetic field detecting means 5, and by rotating the magnetic shield container 6 around the axis as the center of rotation, the relative positional relationship between the magnetic field generating means 2 and the magnetic field detecting means 5 can be changed. In other words, the magnetic shielding container 6 has the magnetic field generating means 2 and the magnetic field detecting means 5 attached thereto, and functions as a rotating member that is freely rotatable by rotation around an axis perpendicular to the scalp 1, with the center of rotation being the center of the line connecting the magnetic field generating means 2 and the magnetic field detecting means 5.

[0039] A brain function measuring method for non-invasively measuring brain functions using the brain function measuring device 100 having the above-mentioned configuration will be described. As shown in Fig. 5, first, in the brain function measuring device 100, a magnetic field 4 is irradiated toward the cerebral cortex 3 at the outermost part of the brain of the subject P using a magnetic field generating means 2 arranged on the scalp 1 of the subject P (step S1). Next, the magnetic field 4 from the magnetic field generating means 2 emanates from the N pole, passes through the cerebral cortex 3, and returns to the S pole in a loop-shaped path. The magnetic field returning as a signal reflecting the activity state of the cerebral cortex 3 is detected by a magnetic field detecting means 5 arranged on the scalp 1 (step S2). The magnetic field detected by the magnetic field detecting means 5 becomes a signal reflecting the activity state of the cerebral cortex 3.

[0040] As can be seen from the above explanation, by using the detection ends 6a shown in Figures 3A, 3B, and 3C in combination with the rotation mechanism (magnetic shielding container 6) shown in Figures 4A and 4B, it is possible to obtain measurement values ​​corresponding to the various orientations of neurons present in the cerebral cortex 3, which has a complex structure.

[0041] As shown in FIG. 6A, a conventional magnetoencephalograph measures vibrations (fluctuations in magnetic field) transmitted from a vibration source (brain activity area) using a distant sensor, and the magnitude of the measured signal is quite small. The magnitude of this signal is about several hundred fT. In contrast, as shown in FIG. 6B, the method according to the present embodiment measures a steady flow that fluctuates due to a vibration source (brain activity area) located in the middle of a flow path (steady magnetic field) downstream, and can measure a relatively large signal. The magnitude of this signal is about 1 to 5 nT.

[0042] [Example] An example of the brain function measuring apparatus 100 and the brain function measuring method according to the present embodiment will be described.

[0043] FIG. 7 shows the brain function measuring device 100 worn on the head of the subject P when a signal induced in the cerebral cortex 3 was measured in response to an electrical stimulation test of the median nerve on the right wrist using 16 measurement points, i.e., 16 measurement sets (detection ends). A ferrite magnet with a diameter of 5 mm and a thickness of 2 mm was used as the magnetic field generating means 2 (see FIG. 1). A highly sensitive sensor "MI-CB-1DH" manufactured by Aichi Micro Intelligent was used as the magnetic field detecting means 5 (see FIG. 1). Furthermore, a magnetic shielding container 6 was used which was made by covering a hollow cylindrical container made of polypropylene with a diameter of 30 mm and a height of 51 mm with a magnetic shielding material F1AH0607 manufactured by Hitachi Metals with a thickness of 0.12 mm. The bottom surface 6a of the magnetic shielding container 6 (hollow cylindrical container made of polypropylene) was open toward the scalp 1 without being covered with a magnetic shielding material.

[0044] The mounting plate 7 (see FIG. 4A) was a plastic disk having a diameter of 26 mm and a thickness of 2.4 mm. In practice, the magnetic field generating means 2 and the magnetic field detecting means 5 were arranged in the magnetic shielding container 6 with a distance of 25 mm therebetween.

[0045] During signal measurement, electrical stimulation with a pulse width of 500 μs and intensity of 3 mA was applied to the median nerve through a surface stimulation electrode. The stimulation interval was set to 1.5 s, and the signal was measured from 100 ms before stimulation to 1000 ms after stimulation. The somatosensory evoked signal was obtained by calculating the arithmetic mean of 200 measurement data.

[0046] 8A and 8B are diagrams showing an overview of the brain function measuring device 100. Fig. 8A shows the arrangement sites (measurement points) of 16 measurement sets (detection ends) on the scalp 1 of the subject P. Fig. 8B shows actual time-series signal waveforms obtained from the magnetic field detection means 5 at the arrangement sites (measurement points) of the 16 measurement sets (detection ends). The graphs of the measurement results of F5, F3, F4, F6, etc. in Fig. 8B are the measurement results at the measurement points F5, F3, F4, F6 in Fig. 8A.

[0047] The measurement set (detection end) was placed at 16 locations (measurement points) in the electrode arrangement of the extended international 10-20 system used for EEG measurement: F3, F4, F5, F6, C3, C4, C5, C6, Cz, CP3, CP4, P3, P4, P5, P6, and Pz. For simplicity, the experiment was performed with the magnetic field direction of each channel aligned from the front to the back of the head.

[0048] The area of ​​the cerebral cortex 3 that is active in response to stimulation of the median nerve of the right hand is the hand region of the primary somatosensory cortex of the left cerebral hemisphere, and the position of the brain function measurement method closest to this area is CP3 on the extended international 10-20 system. When the brain function measurement device 100 and the brain function measurement method according to this embodiment were used, a large amplitude signal was observed localized to the CP3 area, as shown in Fig. 8B, and the effectiveness of the brain function measurement method using the brain function measurement device 100 according to this embodiment was confirmed.

[0049] Somatosensory evoked signals were measured using a prototype 16-channel brain function measuring device 100. As a result of measuring somatosensory evoked signals when electrical stimulation was performed on the median nerve of the left wrist, it was confirmed that a large signal was observed locally in a suitable position on the right hemisphere of the head (the position of CP4 near the hand control area of ​​the primary somatosensory cortex of the brain). This result demonstrated that it is possible to measure with higher spatial accuracy than conventional electroencephalograms and magnetoencephalograms.

[0050] Furthermore, the amplitude of the signal changes depending on the direction of the magnetic field (the direction of the magnetic field detection means 5 as seen from the magnetic field generation means 2). For example, as shown in Fig. 9, at the position of CP4, in the brain function measurement device 100 according to this embodiment, the magnetic shielding container 6 was rotated and measurements were performed in the directions of four magnetic fields that are mutually orthogonal to each other, and it was confirmed that the amplitude of the signal changes depending on the direction of the magnetic field (the direction of the magnetic field detection means 5 as seen from the magnetic field generation means 2). This was the same for the other 15 positions. The ability to measure vector brain signals including information on the direction of the magnetic field is an advantage not available with conventional methods.

[0051] In the above embodiment, the N pole or S pole of the magnetic field generating means 2 is oriented toward the scalp 1, but the present invention is not limited to this. If the magnetic field passes through the cerebral cortex 3, the magnetic field generating means 2 may be installed without oriented toward the scalp 1.

[0052] Various embodiments and modifications of the present invention are possible without departing from the broad spirit and scope of the present invention. The above-described embodiments are for the purpose of explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is indicated by the claims, not the embodiments. Various modifications made within the scope of the claims and the scope of the invention equivalent thereto are considered to be within the scope of the present invention.

[0053] This application claims priority based on Japanese Patent Application No. 2018-214249 filed on November 15, 2018, and the entire specification, claims, and drawings of Japanese Patent Application No. 2018-214249 are incorporated herein by reference. [Industrial Applicability]

[0054] According to the present invention, it is possible to measure the brain activity state with high accuracy using a simple device configuration and simple procedures, and the present invention can be applied to non-invasive measurement of brain function. [Explanation of symbols]

[0055] 1. Scalp 2. Magnetic Field Generating Means 2a Rotation drive means 3. Cerebral cortex 4 Magnetic Field (Static Magnetic Field) 5. Magnetic field detection means 6. Magnetically shielded container 6a Bottom part (detection end) 6b Through hole 7 Installation board 7a axis 10 Analog / Digital Converter 11 Equipment 100 Brain function measuring device P Subject

Claims

1. A brain function measuring device comprising a magnetic field generating means and a magnetic field detecting means, the magnetic field generating means is placed on the scalp of the subject, and generates a static magnetic field which emanates from a north pole, passes through the cerebral cortex of the subject's brain, and returns to a south pole via a loop-shaped path; the magnetic field detection means is disposed on the scalp and detects changes in the static magnetic field; The brain function measuring device measures, by the change in the static magnetic field, an activity state of a part of the brain near a position where the brain function measuring device is placed on the scalp and through which the static magnetic field passes along the loop-shaped path. A brain function measuring device characterized by:

2. The magnetic field generating means is a permanent magnet or an electromagnet. The brain function measuring device according to claim 1 .

3. The magnetic field detection means is any one of a one-axis magnetic field detector, a two-axis magnetic field detector, and a three-axis magnetic field detector. The brain function measuring device according to claim 1 .

4. The present invention further comprises a magnetic shielding container that houses the magnetic field generating means and the magnetic field detecting means and blocks magnetic fields from the outside world that enter from other than the part facing the scalp. The brain function measuring device according to claim 1 .

5. The magnetic field generating means and the magnetic field detecting means are attached to a rotating member having a center of rotation at the center of a line connecting the magnetic field generating means and the magnetic field detecting means, and is configured to be freely rotatable by rotating an axis perpendicular to the scalp. The brain function measuring device according to claim 1 .

6. The magnetic field generating means has a structure that allows the pole facing the scalp to be changed to either a north pole or a south pole. The brain function measuring device according to claim 1 .

7. A brain function measuring method for non-invasively measuring brain function using a brain function measuring device including a magnetic field generating means and a magnetic field detecting means, A static magnetic field is applied to the cerebral cortex, which is the outermost part of the brain of the subject, using a magnetic field generating means arranged on the scalp of the subject; a magnetic field generating means for generating a magnetic field that generates a static magnetic field from the N pole, passes through the cerebral cortex, and returns to the S pole in a loop-like path; a magnetic field detecting means arranged on the scalp detects a change in the returning static magnetic field; The brain function measuring device measures an activity state of a part of the brain near a position where the brain function measuring device is placed on the scalp and through which the static magnetic field passes along the loop-shaped path, by changing the static magnetic field. Methods for measuring brain function.

8. The magnetic field generating means is characterized in that a permanent magnet or an electromagnet is used. The brain function measuring method according to claim 7.

9. The magnetic field detection means is characterized in that any one of a one-axis magnetic field detector, a two-axis magnetic field detector, and a three-axis magnetic field detector is used. The brain function measuring method according to claim 7.

10. The magnetic shielding container that houses the magnetic field generating means and the magnetic field detecting means is used to shield the magnetic field from the outside world that enters from a part other than the part facing the scalp. The brain function measuring method according to claim 7.

11. The magnetic field generating means and the magnetic field detecting means are attached, and a rotating member having an axis perpendicular to the scalp is rotated with the center of rotation being the center of a line connecting the magnetic field generating means and the magnetic field detecting means, thereby changing the relative relationship between the direction in which the magnetic field is irradiated and the direction of the nerve fibers in the cerebral cortex, thereby generating a magnetic field with the magnetic field generating means and detecting the magnetic field with the magnetic field detecting means. The brain function measuring method according to claim 10.

12. The magnetic field generating means changes the direction of the magnetic field irradiated to the cerebral cortex by selecting a pole facing the scalp as a north pole or a south pole, and the magnetic field detecting means detects the magnetic field. The brain function measuring method according to any one of claims 7 to 11.

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