JP4482660B2 - Neural cell stimulation site estimation method and brain function analysis apparatus using the same - Google Patents

Description

  The present invention relates to a method for estimating a nerve cell stimulation site and a brain function analysis apparatus using the method, and more particularly to a method for estimating a nerve cell stimulation site using magnetic stimulation and a brain function analysis device using the method.

  2. Description of the Related Art Conventionally, diagnosis and treatment have been performed by a method in which a magnetic field that changes with time is applied to a living body using a coil, and the brain and nerves are stimulated by an electric field induced in the living body (see, for example, Non-Patent Document 1). The outline will be described with reference to FIG.

  FIG. 11 is a diagram schematically showing the electric field induced by the magnetic stimulation coil.

  In FIG. 11, 12 is a stimulation coil placed parallel to the scalp, 13 is a pulse current flowing through the stimulation coil, 14 is a pulse magnetic field induced by the pulse current, 15 is a stimulating nerve cell, and 16 is a head due to the pulse magnetic field. This is the induced current induced in

  When a pulse current 13 is passed through the stimulation coil 12, a pulse magnetic field 14 is generated in the brain, and an induced current 16 flows in a direction to cancel the magnetic field. When pulse currents that are opposite to each other are simultaneously applied to the circular coils of the stimulation coil 12, the induced current is strengthened immediately below the center of the 8-shaped coil 12, and the nerve cells 15 are stimulated. At this time, the induced current flowing in the nerve cell 15 flows in a plane parallel to the coil, that is, the scalp, and the nerve cell in the same direction as the induced current is stimulated with the highest sensitivity.

  On the other hand, recently, a method for identifying an activation region such as a cranial nerve from a measurement result of a biological function by magnetic resonance imaging (MRI) has been implemented. Conventionally, information provided by MR (Magnetic Resonance) images was mainly anatomical, but in recent years, changes in venous blood and blood flow due to cranial nerve activity have been observed as changes in permeability, Application to brain function measurement is in progress. At this time, it is necessary to extract changes in venous blood from MR images and specify the cranial nerve activation site from the data, but it is difficult to specify the exact position when the activation site is deep in the brain There is a point.

  As a method for solving these problems, for example, the following methods have been proposed.

  One method is to extract only the gray matter (cerebral cortex) in which many nerve cells are present from the MR image including the morphological information, and to include the functional information in the image, in identifying the cranial nerve activation site from the MR image. The MR image is superimposed three-dimensionally to improve the identification accuracy of the activated region (see, for example, Patent Document 1).

As another method, an MR image including functional information in the image is measured in time series, and time differentiation of time series data of magnetic resonance signals is obtained for each pixel of the image, and activation is performed from the time differentiation data. A region is identified (for example, see Patent Document 2).
Journal of Applied Physics, Vol.67, No9. May 1990 JP 9-47438 JP-A-8-131414

  The method described in Patent Document 1 can improve the identification accuracy of the activated region by extracting only the gray matter (cerebral cortex) in which many nerve cells are present, but requires an MR image including functional information. Yes, the measurement work becomes complicated.

  In addition, the method described in Patent Document 2 can identify the activated region with high accuracy by processing a lot of time-series data, but requires an MR image including functional information for each time, and measurement. Work becomes complicated.

  The present invention has been made in view of the problems, and firstly, the step of taking an image of a region including nerve cells of a living body and the nerve cells were generated by stimulating the nerve cells electromagnetically by a stimulation coil from outside the living body. A step of setting a component parallel to the nerve cell of an induced electric field as a stimulation amount of the nerve cell and a step of estimating a site having a large stimulation amount as a stimulation site of the nerve cell are provided. is there.

  The component of the induced electric field parallel to the nerve cell is a component in a unit vector direction perpendicular to the surface including the nerve cell.

  Second, a step of taking an image of a brain of a living body, and electromagnetic stimulation of the cerebral cortex of the brain by a stimulation coil from the outside of the living body so that the induced electric field generated on the surface of the cerebral cortex And a step of setting a component having a large amount of stimulation as a stimulation site of the nerve cell.

  Third, capturing a brain image of a living body, calculating a unit vector perpendicular to the surface of the cerebral cortex, electromagnetically stimulating the cerebral cortex from outside the living body with a stimulation coil, Calculating the inner product of the induced electric field generated in the unit vector perpendicular to the surface to be the stimulation amount of the nerve cell, estimating the large stimulation amount site as the stimulation site of the nerve cell, It solves by having.

  Fourth, a step of taking an image of the brain of a living body, and electromagnetic stimulation of the cerebral cortex of the brain by a stimulation coil from the outside of the living body, and perpendicular to the surface of the induced electric field generated on the surface of the cerebral cortex A step of setting a stimulus component of the pyramidal neuron as a stimulus amount, a step of setting a component parallel to the brain surface of the induced electric field as a stimulus amount of the interneuron, and a large stimulus amount of the cone neuron and the interneuron And a step of estimating each part as a stimulation part.

  Fifth, taking an image of the brain of a living body, calculating a unit vector perpendicular to the surface of the cerebral cortex, and electromagnetically stimulating the cerebral cortex from the outside of the living body with a stimulation coil, and generating on the surface Calculating an inner product of the induced electric field and a unit vector perpendicular to the surface to obtain a stimulus amount of the pyramidal neuron, and calculating a component parallel to the surface of the induced electric field by the stimulus amount of the pyramidal neuron And the step of setting the stimulation amount of the interneuron and the step of estimating the pyramidal neuron and the region where the stimulation amount of the interneuron is large as the respective stimulation site.

  The unit vector perpendicular to the surface may be calculated by dividing the image into a pixel group including a boundary between the brain and the brain, identifying a brain surface pixel from the pixel group, and the brain surface. Extracting a cubic pixel group consisting of pixels in a row × column × stage centered on the pixel, selecting a pixel outside the brain from the cubic pixel group, and the brain in the cubic pixel group from the brain surface pixel Calculating at least one unit vector for an outer pixel; and calculating a unit vector perpendicular to the surface by normalizing a sum of the unit vectors. is there.

  Further, the brain surface pixels are constituted by pixels in the brain adjacent to the pixels outside the brain.

  The cubic pixel group includes 27 pixels of 3 rows × 3 columns × 3 stages.

  Sixth, active part acquisition means for acquiring the active part of the brain of the living body, stimulation part estimation means for estimating the stimulation part of the brain neurons by externally stimulating the active part, and the magnetic stimulation It solves by comprising the biological reaction measuring means which measures the reaction of the said induced | generated biological body.

  The active site acquisition means acquires the active site of the brain that moves in relation to higher brain functions of the brain of the living body.

  The stimulation site estimation means calculates the stimulation amount of the brain cone neuron by the magnetic stimulation and estimates the stimulation site of the cone neuron.

  The stimulation site estimation means calculates a stimulation amount of the brain interneuron by the magnetic stimulation, and estimates the stimulation site of the interneuron.

  In other words, the present invention eliminates the problems of the method of identifying the activation region such as the cranial nerve from the biological function measurement result, and provides a method that allows the site stimulated by the magnetic stimulation to be identified with high accuracy by a relatively simple operation. There is to do.

  A further object of the present invention is to identify brain activity sites with high accuracy to provide data important for determination of emotion expression processes, memory recall processes, cognitive processes, etc., identification of dysfunctional sites, etc. An object of the present invention is to provide a method for identifying a brain stimulation site with magnetism with high accuracy, which can be applied to a function measurement system.

  According to the method for estimating a nerve cell stimulation site of the present invention, first, in order to obtain a stimulation amount at that point as an inner product of an electric field induced in a living body by a magnetic stimulation coil and a unit vector in the nerve cell direction. This makes it possible to accurately estimate the amount of stimulation. Further, since the point at which the amount of stimulation is greater than other sites is estimated as the stimulation site under that condition, it is possible to estimate the stimulation site more accurately than in the conventional method.

  Secondly, the amount of stimulation at that point is evaluated as the inner product of the electric field induced in the cerebral cortex by the magnetic stimulation coil and the unit vector perpendicular to the surface of the cerebral cortex, and the amount of stimulation becomes larger than other regions. Is estimated as a cerebral cortical stimulation site under that condition, so that it is possible to estimate the stimulation site of the brain neurons more accurately than in the conventional method.

  Third, the amount of stimulation at that point is evaluated as the inner product of the electric field induced in the cerebral cortex by the magnetic stimulation coil and the unit vector perpendicular to the surface of the cerebral cortex, and the amount of stimulation becomes larger than other regions. Is estimated as a cerebral cortical stimulation site under the above conditions, the brain surface pixels are extracted from the density of the pixels of the magnetic resonance image, and then 3 × 3 × 3 (= 27) centering on the brain surface pixels A cubic pixel group of pixels is extracted, and for the 26 pixels excluding the brain surface pixels, whether or not they are in the brain or outside the brain is determined from the shading, and determined to be outside the brain from the brain surface pixels A vector group for all the pixels is calculated, a sum vector of the vector group is obtained, and a unit length vector in the sum vector direction is set as a unit vector perpendicular to the brain surface pixel. Thereby, the stimulation site | part of a cerebral cortex can be estimated simply.

  Fourthly, for the entire brain surface, it is possible to simultaneously obtain a region where the amount of stimulation of the pyramidal neurons and interneurons increases. That is, it is possible to simultaneously estimate the stimulation site of a pyramidal neuron and the stimulation site of an interneuron for a certain magnetic stimulation.

  Fifth, the amount of stimulation at that point is evaluated as the inner product of the unit vector perpendicular to the surface of the cerebral cortex and the electric field induced in the head by the stimulation coil for electromagnetically stimulating cerebral cortex neurons, Since the point where the amount of stimulation is greater than other regions is estimated as the cerebral cortical stimulation site under that condition, it is possible to estimate the stimulation site more accurately than the conventional method, and the judgment and function of emotion expression process, cognitive process, etc. It is possible to provide data that is important for identifying the faulty part.

  We have devised a method for accurately identifying the stimulation site when magnetically stimulating a site where many nerve cells such as the brain are present.

  The technique of the present invention is effective when estimating stimulation sites of nerve cells such as the brain, spinal cord, and peripheral nerve. By obtaining a unit vector group along the nerve fiber (nerve cell) direction for each pixel on the surface of the peripheral nerve and the spinal cord from MR images of the brain, spinal cord, and peripheral nerve, and calculating the inner product with the electric field induced by magnetic stimulation A site where the component of the induced electric field in the nerve fiber direction is high can be estimated as the stimulation site.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a flowchart showing a procedure of a method for estimating a nerve cell stimulation site in magnetic stimulation.

  As shown in FIG. 1, the method for estimating the stimulation site of a nerve cell according to the present embodiment includes a step of taking an image of a region including a nerve cell of a living body and electromagnetically stimulating the nerve cell from outside the living body by a stimulation coil. The step of setting a component parallel to the nerve cell of the generated induced electric field as the stimulation amount of the nerve cell, and the step of estimating the portion having the large stimulation amount as the stimulation site of the nerve cell are configured.

  First step: a step of taking an image of a region including nerve cells of a living body (FIG. 1 (1)).

  An MR image of the surface of a region containing many nerve cells such as the brain, spinal cord and peripheral nerve is taken. In the case of the brain, it is the cerebral cortex (brain surface), and in the spinal cord and peripheral nerves, the nerve cells are mainly ruptured due to damage, terminal sites, synaptic sites where the nerve cells are connected, and the like.

  Second Step: Steps of electromagnetically stimulating the nerve cell from outside the living body by a stimulation coil and setting a component parallel to the nerve cell of the generated induced electric field as a nerve cell stimulation amount (FIGS. 1 (2) to (4) )).

  Based on the MR image of the surface of the region containing many nerve cells, the distribution of unit vectors parallel to the long axis direction of the nerve cells is calculated for each unit pixel (FIG. 1 (2)).

  Then, the electric field distribution induced | guided | derived to the surface containing many nerve cells in the living body by magnetic stimulation from outside the living body is obtained (FIG. 1 (3)).

  Furthermore, the distribution of components parallel to the long axis direction of the induced electric field is calculated by the inner product of the induced electric field and the unit vector parallel to the long axis direction of the nerve cell, and the stimulation amount of the nerve cell is calculated. (FIG. 1 (4)).

  3rd step: The step which estimates the site | part with a large stimulation amount as the stimulation site | part of a nerve cell (FIG. 1 (5)).

  It is considered that the value of the induced electric field is intensively increased at the site affected by the external magnetic stimulation. Therefore, the part where the component of the induced electric field parallel to the long axis direction of the nerve cell is larger than the other part is estimated as the stimulation part of the nerve cell.

  Hereinafter, with reference to FIGS. 2 to 7 as the first embodiment, the case of the brain will be described as an example.

  The method for estimating a nerve cell stimulation site according to the first embodiment includes a step of taking an image of a brain of a living body, a step of calculating a unit vector perpendicular to the surface of the cerebral cortex, and a stimulation coil from the outside of the living body. Electromagnetically stimulating the cerebral cortex, calculating an inner product of an induced electric field generated on the surface and a unit vector perpendicular to the surface to obtain a stimulation amount of the nerve cell; And a step of estimating a nerve cell stimulation site.

  1st step: The step which image | photographs the image of the brain of a biological body (FIG. 1 (1)).

  First, an MR image of a subject is acquired by MRI. FIG. 2 is a diagram showing an MR image of a horizontal section of the brain, and FIG. 2 (A) is an acquired MR image 1. As shown in the figure, the MR image 1 is composed of a two-dimensional image having gray scale information. A three-dimensional image of the brain is constructed by continuously acquiring horizontal tomographic images of the head like the MR image 1 at regular intervals (for example, at intervals of about 1 mm).

  FIG. 2B is an enlarged view schematically showing a part of the pixel group 2 in FIG. As described above, when the pixel group 2 at the boundary between the brain and the non-brain portion is extracted, the brain (inside the brain) and the non-brain portion (outside the brain) can be distinguished by the color density of the pixels. In the MR image 1 and the pixel group 2 in FIG. 2, the parts other than the brain are shown in white, but in the normal MRI image, the parts other than the brain have a color close to black. In the present embodiment, the outside of the brain is displayed in white and the inside of the brain is displayed in black.

  FIG. 3 is a diagram showing the pixel group 2 including the boundary between the outside of the brain and the inside of the brain. In the present embodiment, the MR image 1 acquired by MRI is divided into pixels of a predetermined unit (for example, about 1 mm × 1 mm), and the pixel group 2 including the boundary between the brain and the brain is extracted. It is known that neurons are arranged almost perpendicular to the surface of the cerebral cortex. Therefore, in this embodiment, the cerebral cortex, that is, the brain surface is specified in order to specify the direction of the nerve cell, and the direction perpendicular to the brain surface is set as the direction of the nerve cell. The brain surface can be specified by discriminating inside and outside the brain based on the MR image. Therefore, the pixel group 2 including inside and outside the brain is extracted from the MR image.

  Then, a brain surface pixel is specified from the pixel group 2. The brain surface pixel is identified by selecting an arbitrary intracerebral pixel 21 and determining whether the intracerebral pixel 21 is a brain surface based on the color density of the pixels around the intracerebral pixel 21. In order to specify the brain surface, it is necessary to pay attention to the upper and lower pixels with respect to an arbitrary intracerebral pixel 21. For this reason, in the present embodiment, the brain surface pixels are specified using three MR images that are continuous in a vertical direction at a predetermined interval (for example, about 1 mm).

  FIG. 4 shows a pixel group 3 in which three pixel groups 2 are extracted continuously in the vertical direction. Pixel groups A, B, and C are a part of three consecutive MR images including the boundary between the brain and the outside of the brain, and are composed of, for example, a pixel group composed of arbitrary 6 × 6 pixels. . When an arbitrary intracerebral pixel 21 (black) is selected from the pixel groups A, B, and C, and at least one pixel out of a total of 26 pixels around the intracerebral pixel 21 exists, The pixel is a brain surface pixel 23.

  FIG. 4 is a diagram illustrating a pixel group that is continuous above and below a pixel group that includes a boundary between the outside of the brain and the inside of the brain. For example, the brain pixel 21 in the fifth row and the fourth column of the pixel group B shown in FIG. 4 (denoted as B [4] [3]; the same applies hereinafter) is selected (here, hatched). The pixels adjacent to the brain pixel 21 are 3 × 3 (= 9) pixels centered on A [4] [3] located above B [4] [3] in the pixel group A, and the pixel group. Among 3 × 3 (= 9) pixels centered on B [4] [3] in B, 8 pixels excluding B [4] [3] and B [4] [3] in pixel group C This is a total of 26 pixels of 3 × 3 (= 9) pixels centered on C [4] [3] located below. Among them, A [3] [2], A [3] [3], A [4] [4], B [3] [3], B [3] [4], B [4] [4], C Since [3] [3] and C [4] [4] are white, B [4] [3] can be regarded as the brain surface pixel 23.

  Then, a cubic pixel group 25 made up of rows × columns × stages centered on the brain surface pixel 23 is extracted, and the extra-cerebral pixel 22 in the cubic pixel group 25 is specified.

  For example, a cubic pixel group 25 of 3 × 3 × 3 (= 27) pixels around the B [4] [3] brain surface pixels 23 is extracted. Among the cubic pixel group 25, A [3] [2], A [3] [3], A [4] [4], B [3] [3], B [3] [4], B [ 4] [4], C [3] [3], and C [4] [4] are white, and thus these pixels are specified as extra-brain pixels 22 for one brain surface pixel 23.

  Second step: a step of calculating a unit vector perpendicular to the surface of the cerebral cortex (FIG. 1 (2)).

  FIG. 5 is a diagram showing a vector from the brain surface pixel 23 to the extra-cerebral pixel 22. As described above, the nerve cells are arranged perpendicular to the surface of the cerebral cortex. Therefore, in the present embodiment, in order to specify the cerebral cortex, that is, the direction perpendicular to the brain surface, the 26 pixels excluding the brain surface pixel 23 from the cubic pixel group 25 are used in the brain from the density. Determine whether it is outside the brain. Then, vectors from the brain surface pixels 23 to all pixels determined to be outside the brain are calculated, and one or a plurality of unit vectors 4 or unit vector groups 4 in the vector direction are calculated. Then, the unit vector 26 or the unit vector group 4 is normalized to calculate a unit vector 26 perpendicular to the surface of the cerebral cortex (brain surface).

  FIG. 6 is a diagram showing a unit vector 26 perpendicular to the brain surface. The unit vector 26 perpendicular to the brain surface is obtained as a unit vector in the direction of the sum vector by obtaining a sum vector of the calculated unit vector groups. This is repeated, and the distribution of unit vectors 26 perpendicular to the brain surface is calculated over the entire surface of the brain.

  Third step: The cerebral cortex is electromagnetically stimulated from outside the living body by a stimulation coil, and an inner product of an induced electric field generated on the surface, a unit vector perpendicular to the surface, and the induced electric field is calculated, and the nerve It is set as the amount of cell stimulation (FIGS. 1 (3) and (4)).

  Here, the electric field distribution induced in the living body by magnetic stimulation is calculated.

  FIG. 7 is a diagram schematically showing an induced electric field and nerve cells when a cerebral cortex, that is, a brain surface is stimulated from outside the living body using a magnetic stimulation coil or the like.

  It is known that brain neurons (cone cells or cone neurons) 8 are arranged perpendicular to the brain surface 7. In addition, when the nerve cell 8 is stimulated with an electric field, it is known that the magnitude of the electric field component in the long axis direction of the nerve cell 8 becomes a stimulation amount, and excitement occurs at the end of the nerve cell 8.

  That is, when magnetic stimulation is performed by the external magnetic stimulation coil 5, an electric field (induced electric field) 6 is induced by the magnetic stimulation coil 5 starting from the brain surface 7, and this distribution is calculated (FIG. 1 (3)). .

  In this embodiment, the inner product of the unit vector 26 perpendicular to each brain surface obtained by the method as shown in FIGS. 5 and 6 and the electric field 6 induced by the magnetic stimulation coil 5 is calculated. The component 9 perpendicular to the brain surface 7 of 6 is calculated, and its distribution is obtained. Then, the component 9 perpendicular to the brain surface of the electric field is set as the stimulation amount at that position (FIG. 1 (4)).

  FIG. 7 schematically shows a cross section of the brain, and the position of the magnetic stimulation coil 5 does not have to be parallel to the scalp (brain surface 7). Since the electric field 6 is generated in the brain no matter where and on the scalp the magnetic stimulation coil 5 is placed, the position of the magnetic stimulation coil 5 is not limited.

  Fourth step: A site having a large amount of stimulation is estimated as a nerve cell stimulation site (FIG. 1 (5)).

  The component 9 perpendicular to the brain surface of the electric field is calculated for all parts of the brain surface 7, that is, all the brain surface pixels 23. Then, the part of the brain surface 7 in which the component 10 greater than the other parts among the components 9 perpendicular to the brain surface 7 of the induced electric field 6 in the magnetic stimulation is estimated as the stimulation part 11.

  Next, a second embodiment of the present invention will be described with reference to FIGS.

  FIG. 8 is a schematic cross-sectional view showing the cerebral cortex. As shown in FIG. 8, the structure of the cerebral cortex is composed of nerve cells (cone neurons) 8 that perform input and output to other parts, and interneurons 28 that exchange information between the cone neurons 8 via synapses. ing. As described above, the pyramidal neuron 8 is substantially parallel to the brain surface 7, and the interneuron 28 runs substantially parallel to the brain surface 7.

  In the first embodiment, a unit vector 26 perpendicular to the brain surface is obtained, and the inner product with the electric field 6 induced by the external magnetic stimulation is used as the stimulation of the nerve cell (cone neuron) 8 in the brain surface pixel 23. The amount. That is, a region where the stimulation amount of the pyramidal neurons 8 arranged substantially perpendicular to the brain surface 7 is large is estimated as a stimulation region.

  In the second embodiment, the stimulation amount of the pyramidal neuron 8 is obtained, and the stimulation amount of the interneuron 28 that plays an important role in information processing of the brain is also obtained, and the stimulation site is estimated.

  FIG. 9 is a diagram showing a component perpendicular to the brain surface 7 of the electric field E induced by the pyramidal neurons 8 and the interneurons 28 and the interneurons 28 in the brain surface and the magnetic stimulation (hereinafter referred to as an electric field vertical component Ev). It is the schematic cross section which showed two-dimensionally the relationship with the component (henceforth electric field parallel component Ep) parallel to the brain surface 7 of the induced electric field E. FIG.

  Here, the induced electric field E is the electric field 6 in FIG. 7, and the electric field vertical component Ev is a component 9 perpendicular to the brain surface 7 of the electric field 6 in FIG. The electric field parallel component Ep is a component 20 parallel to the brain surface 7 of the electric field 6 indicated by a black thin line in FIG.

  In this embodiment, it is considered that the electric field vertical component Ev runs parallel to the pyramidal neuron 8 and the electric field parallel component Ep runs parallel to the interneuron 28, and the stimulation amount of the nerve cell is calculated by individually calculating these stimulation amounts. The site can be estimated in more detail.

  In the first embodiment, the electric field vertical component Ev is calculated over the entire brain surface. That is, in each brain surface pixel of the brain surface 7 where the electric field vertical component Ev is calculated, the electric field parallel component Ep can be calculated from the electric field vertical component Ev and the electric field E. Accordingly, by obtaining a site having a large value, it is possible to estimate a stimulation site not only for the pyramidal neuron 8 but also for the interneuron 28.

  Hereinafter, a specific description will be given with reference to the flowchart of FIG.

  The method for estimating a nerve cell site according to the second embodiment includes a step of taking a brain image of a living body, calculating a unit vector perpendicular to the surface of the cerebral cortex, and using the stimulation coil from the outside of the living body to stimulate the cerebral cortex. Stimulating electromagnetically, calculating an inner product of an induced electric field generated on the surface and a unit vector perpendicular to the surface to obtain a stimulation amount of the pyramidal neuron of the nerve cell, and a stimulation amount of the pyramidal neuron Calculating a component parallel to the surface of the induced electric field to obtain a stimulation amount of the interneuron of the nerve cell, and estimating a stimulation area of the pyramidal neuron and the interneuron as a stimulation area Steps.

  Since the first step and the second step are the same as those in the first embodiment, description thereof is omitted.

  Third step: The cerebral cortex of the brain is electromagnetically stimulated by a stimulation coil from outside the living body, and the inner product of the induced electric field generated on the surface and the unit vector perpendicular to the surface is calculated to calculate the pyramidal neuron of the neuron. The amount of stimulation.

  Similar to the first embodiment, the distribution of the induced electric field E in each brain surface pixel 23 of the brain surface 7 is calculated (FIG. 1 (3)). Then, by the inner product of the induced electric field E and the unit vector perpendicular to the surface of the cerebral cortex (brain surface), the distribution of the component (electric field vertical component) Ev perpendicular to the brain surface 7 of the induced electric field E generated in each brain surface pixel 23 is obtained. The amount of stimulation of the cone neuron 8 is obtained by calculation. This is repeated, and the distribution of the electric field vertical component Ev is calculated for all brain surfaces 7 (FIG. 1 (4)).

  Fourth step: A component parallel to the brain surface of the induced electric field is calculated based on the stimulation amount of the pyramidal neurons, and is set as the stimulation amount of the interneuron of the nerve cell.

  A component (electric field parallel component) Ep parallel to the brain surface of the induced electric field E is expressed by the following expression by the induced electric field E and the electric field vertical component Ev.

Ep = (| E | ² − | Ev | ² ) ^(1/2)
Thus, the electric field parallel component Ep is calculated over the entire brain surface 7 to obtain the distribution thereof, and the stimulation amount of the interneuron 28 is obtained.

  Fifth step: Sites with large amounts of stimulation of cone neurons and interneurons are estimated as the respective stimulation sites.

  A region where the amount of stimulation of the pyramidal neuron 8 is larger than the other region is specified, and the region is estimated as the stimulation region of the pyramidal neuron 8. Similarly, a part where the stimulation amount of the interneuron 28 is larger than the other part is specified, and the part is estimated as the stimulation part 28 of the interneuron (see FIG. 1 (5)).

  Here, a portion where the electric field vertical component Ev is large is not necessarily a portion where the electric field horizontal component Ep is large. In the present embodiment, with respect to the entire brain surface 7, it is possible to simultaneously obtain a region where the stimulation amounts of the pyramidal neuron 8 and the interneuron 28 are increased. That is, it is possible to simultaneously estimate the stimulation site of the pyramidal neuron 8 and the stimulation site of the interneuron 28 for a certain magnetic stimulation.

  Therefore, it is possible to estimate separately the input / output part of the brain stimulated by magnetic stimulation and the part involved in information processing, which is very useful for analyzing the function of the brain.

  The effect of the above estimation method will be described using a motor area as an example. In the motor area, the cone neuron 8 is the exit from which the motion command goes out to the arm or leg. The pyramidal neurons 8 at the exit of the command communicate with each other through interneurons 28 that run parallel to the brain surface 7, and complex motor commands such as coordinated motions are transmitted to these complexly coupled interneurons 28. It is thought that it is made by the net.

  In the magnetic stimulation of the brain, the pyramidal neuron 8 and the interneuron 28 are simultaneously stimulated by the induced electric field. According to the second embodiment, a large value of the electric field vertical component Ev and a large value of the electric field horizontal component Ep are individually calculated, and the stimulation part of the pyramidal neuron 8 and the stimulation part of the interneuron 28 are estimated respectively. Thus, it is possible to individually know the site where the pyramidal neuron 8 is stimulated and the site where the interneuron 28 is stimulated.

  Thereby, the exit of the motion command can be estimated by the pyramidal neuron 8, and it can be estimated where and how the complex motion command (motion information) is modified for the command by the interneuron 28. Conceivable.

  Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment is a brain function analysis apparatus using the above estimation method.

  10A and 10B are diagrams for explaining the brain function analysis apparatus 40. FIG. 10A shows a functional block diagram of the brain function analysis apparatus 40, and FIG. 10B shows a schematic diagram explaining the active site of the brain. Show.

  The brain function analysis apparatus 40 includes at least an active site acquisition unit 401, a stimulation site estimation unit 402, and a biological reaction measurement unit 403.

  The active part acquisition means 401 is a means for acquiring an active part of the brain that moves in relation to higher brain functions of the living brain such as an emotion expression process, a memory recall process, and a cognitive process. For example, functional nuclear magnetic resonance imaging, brain magnetic field measuring devices, brain function measuring devices such as electroencephalographs. By using these devices, as shown in FIG. 10B, it is possible to specify the movement 18 of the active region of the brain 17 that is active in relation to the emotion expression process, the memory recall process, the cognitive process, and the like. In other words, these devices can investigate the movement of the spontaneous activity site of the brain over time.

  However, even with this alone, it is impossible to know in detail what function the active site has even if the active site of the brain is known. Therefore, by performing magnetic stimulation aiming at the active site of the brain and observing the phenomenon that occurs at that time, it is possible to estimate what function the site has. That is, after measuring the brain activity site with the brain function measuring device 401, the brain is magnetically stimulated, and the stimulation site estimation unit 402 estimates the nerve cell stimulation site 19, thereby analyzing the function of the stimulation site 19. can do.

  The stimulation site estimation means 402 uses the nerve cell stimulation site estimation method according to the first embodiment to apply an emotional expression process, a memory recall process, and a magnetic stimulation from the outside to the brain 17 of the living body. It is a means for estimating a stimulation site 19 of a nerve cell that moves 18 in relation to a cognitive process or the like. Alternatively, it is a means for estimating the stimulation site 19 of the pyramidal neuron and the interneuron by the method for estimating the stimulation site of the nerve cell of the second embodiment.

  Specifically, the stimulation site estimation unit 402 calculates the stimulation amount of nerve cells (cone neurons) in the brain 17 when magnetic stimulation is performed by a magnetic stimulation device or the like, and estimates the stimulation site 19 of the nerve cells. . Also, the amount of stimulation of interneurons of the brain 17 by magnetic stimulation is calculated, and the stimulation site of the interneurons is estimated.

  The biological reaction measuring means 403 is a device for examining a biological reaction (phenomenon) induced by magnetic stimulation. For example, an electromyograph that examines the movements induced by magnetic stimulation, or a device that examines the change in the correct answer rate when magnetically stimulating a brain region related to memory (how accurately you can memorize what you should memorize) A device for measuring an event (phenomenon) to be analyzed, such as an evaluation based on a correct answer rate, is appropriately selected.

  In this way, in combination with the brain function measuring device 401 such as functional nuclear magnetic resonance imaging and brain magnetic field measurement, the movement 18 of the part of the brain 17 that is active in relation to the emotion expression process, memory recall process, cognitive process, etc. Identify. Then, using the method of the first or second embodiment, the electromyogram induced by performing magnetic stimulation of the part 19 that is active in relation to the emotion expression process, the memory recall process, the cognitive process, etc. By examining the reaction of the living body, a device for examining brain function in detail can be constructed.

As described above, in the present embodiment, the method for estimating brain neurons is described as an example. However, the present invention is not limited thereto, and is effective in estimating the stimulation site of nerve cells in the spinal cord and peripheral nerves. That is, a unit vector group along the nerve fiber direction is obtained from the MRI images of the spinal cord and peripheral nerve for each pixel on the surface of the peripheral nerve and the spinal cord, and the inner fiber with the electric field induced by magnetic stimulation is obtained to obtain the nerve fiber of the induced electric field. A site where the direction component is higher than other sites can be estimated as a stimulation site. Unlike the brain, the spinal cord and peripheral nerves have a cable-like shape, but from MRI images at sites where nerve fibers have been ruptured due to injury, nerve fiber end sites, and synapse sites where nerve fibers are connected For each pixel, a unit vector group along the nerve fiber direction is obtained, and by calculating the inner product with the electric field induced by magnetic stimulation, a part where the component of the induced electric field in the nerve fiber direction is highest can be estimated as the stimulation part. it can.

It is a flowchart which shows the procedure of the estimation method of the nerve cell stimulation site | part in the magnetic stimulation of this invention. It is an MRI image of the brain. It is a figure which shows the pixel group containing the boundary between the brain outside of this invention, and a brain. It is a figure which shows the pixel group which followed the upper and lower sides of the pixel group containing the boundary between the brain outside of this invention, and a brain. It is a figure which shows the vector which goes from a brain surface pixel of this invention to an extracerebral pixel. It is a figure which shows a unit vector perpendicular | vertical to the brain surface of this invention. It is a schematic cross section which shows the induction electric field and nerve cell of the brain surface of this invention. It is a schematic cross section which shows the cerebral cortex of this invention. It is a schematic cross section which shows the induction electric field of the brain surface of this invention. FIG. 2A is a block diagram showing a brain function analysis apparatus according to the present invention, and FIG. 2B is a schematic diagram for explaining an active part of the brain. It is the figure which showed typically the electric field induced | guided | derived by a magnetic stimulation coil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 MRI image of horizontal cross section of brain 2 Pixel group including boundary between outside and inside of brain 3 MRI image of 3 horizontal cross sections of brain continuously up and down 4 Vector heading from brain surface pixels to pixels determined to be outside brain (group)
5 Magnetic stimulation coil 6, E Electric field induced by magnetic stimulation 7 Brain surface 8 Nerve cells (cone cells, cone neurons)
9. Ev Component perpendicular to the brain surface of the electric field induced by magnetic stimulation 10 Component greater than other parts of the component perpendicular to the brain surface of the electric field induced by magnetic stimulation 11 Presumed as the stimulation site in the magnetic stimulation Region 12 Magnetic Stimulation Coil 13 Pulse Current 14 Flowing in Magnetic Stimulation Coil 15 Pulsed Magnetic Field 15 Nerve Cell 16 Induced Electric Field 17 Brain 18 Movement of Region Active in Relation to Emotional Expression Process, Memory Recall Process, Cognitive Process, etc. 19 Brain Limited magnetic stimulation part 20 of the part that is active in relation to the emotional expression process, memory recall process, cognitive process, etc., component parallel to the brain surface of the electric field induced by Ep magnetic stimulation 21 Intracerebral pixel 22 Extracerebral Pixel 23 Brain surface pixel 25 Cubic pixel group 26 Unit vector perpendicular to the brain surface 28 Interneuron 40 Brain function analysis device 401 Active site acquisition means 402 Stimulation site estimation means 03 biological reaction measurement means

Claims (6)

  An activity site acquisition means for acquiring an activity site of a brain of a living body;
  Magnetically stimulate the active site from the outside, take an image of the brain, divide the image to extract a group of cubic pixels including a boundary between brain pixels and extra-cerebral pixels, and around the brain pixels One brain surface pixel is specified by the color density of a certain pixel, and a unit vector or a unit vector group from the brain surface pixel to all the extra-brain pixels is calculated in a cubic pixel group centered on the brain surface pixel. Normalizing these sums and calculating the distribution of unit vectors perpendicular to the surface over the entire surface of the brain to estimate the stimulation site of neurons in the brain;
  A biological reaction measuring means for measuring a response of the living body induced by the magnetic stimulation;
The brain function analysis apparatus characterized by comprising.   In a cubic pixel group including a boundary between the intracerebral pixel and the extracerebral pixel, if a light color pixel exists in one or more pixels around the intracerebral pixel, the light color pixel is identified as the brain surface pixel. The brain function analysis apparatus according to claim 1.   The brain function analysis apparatus according to claim 1, wherein the cubic pixel group includes 27 pixels of 3 rows x 3 columns x 3 stages.   The brain function analysis apparatus according to claim 1, wherein the active site acquisition unit acquires the active site of the brain that moves in relation to a higher brain function of the brain.   The stimulation site estimation means calculates a component perpendicular to the surface of the brain of an electric field induced by the magnetic stimulation from a distribution of unit vectors perpendicular to the surface of the brain, and calculates a stimulation amount of the pyramidal neurons of the brain. The brain function analysis apparatus according to claim 1, wherein the brain function analysis device calculates and estimates a stimulation site of the pyramidal neuron.   The stimulation site estimation means calculates a component parallel to the brain surface of an electric field induced by the magnetic stimulation from a distribution of unit vectors perpendicular to the brain surface, and calculates an interneuron of the brain by the magnetic stimulation. The brain function analysis apparatus according to claim 5, wherein a stimulation amount is calculated and a stimulation site of the interneuron is estimated.

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