Patent Publication Number: US-2020275872-A1

Title: Brain function measurement apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The related application number JP2016-164089, Brain function measurement apparatus, Aug. 24, 2016, Ryu Konoshita and Rintaro Yamamoto, upon which this patent application is based, is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a brain function measurement apparatus, particularly, a brain function measurement apparatus comprising a plurality of measurement probes arranged on the head of a subject. 
     Description of the Prior Art 
     Brain function measurement apparatuses comprising multiple measurement probes arranged on the head of a subject are known in the prior art. Such a brain function measurement apparatus is disclosed, for example, in Japanese Unexamined Patent Application Publication 2015-33561. 
     The aforementioned Japanese Unexamined Patent Application Publication 2015-33561 discloses a brain function measurement apparatus comprising a plurality of measurement probes which are arranged on the head of a subject. This brain function measurement apparatus is provided with a holder which is fitted to the head of a subject and has a plurality of attachment parts. The holder is designed to have measurement probes inserted into any one of the plurality of attachment parts. The brain function measurement apparatus is furthermore designed such that measurement light is applied to the head of the subject from one of a plurality of measurement probes, and measurement light scattered or reflected from inside the brain in the subject&#39;s head is received by the other measurement probes. 
     Here, in a conventional brain function measurement apparatus as described in aforementioned Japanese Unexamined Patent Application Publication 2015-33561, when a measurement probe is to be arranged in a hair-covered area (a site where there is hair) on the subject&#39;s head, the head surface is exposed to the attachment part of the holder by parting the hair using a rod-shaped tool, so that the hair will not interfere with the measurement light. After measurement probes have been attached to the attachment parts, if the magnitude of the signal acquired by the brain function measurement apparatus is not within a specified range, correction of the installation state (installation angle, etc.) of the measurement probes may be performed, or an operation may be performed whereby some of the measurement probes are temporarily removed, the hair is again parted using a rod-shaped tool, and then the measurement probe is reinserted into the attachment part. The above-described operations to ensure that the magnitude of the signal acquired by the brain function measurement apparatus is within the specified range will be referred to hereinafter as “adjustment operations”. 
     Moreover, there are cases where the brain function measurement apparatus as described in aforementioned Japanese Unexamined Patent Application Publication 2015-33561 may be used, for example, at locations exposed to sunlight, locations exposed to illumination light, locations where light is emitted by another measurement instrument, and the like. In such cases, if light other than the measurement light enters the measurement probes, it will become a source of noise. In this connection, one may consider attaching a light blocking member to cover the measurement probes after attaching the measurement probes to the holder, so as to prevent sunlight, illumination light or other external light from entering the measurement probes. 
     However, when a light blocking member is attached to cover the measurement probes in a conventional brain function measurement apparatus such as that of aforementioned Japanese Unexamined Patent Application Publication 2015-33561, the light blocking member will contact the measurement probes, which may alter the installation state of the measurement probes, making it impossible to correctly measure the signal. In such cases, it becomes necessary to perform the aforementioned adjustment operations again, so the efficiency of the measurement preparation operations for the brain function measurement apparatus decreases. Therefore, a brain function measurement apparatus has been desired, which would make it possible to prevent light other than measurement light from entering the measurement probes while avoiding reduction in efficiency of measurement preparation operations. 
     SUMMARY OF THE INVENTION 
     This invention was made to resolve the problem described above. It is an object of this invention to provide a brain function measurement apparatus capable of preventing light other than measurement light from entering the measurement probes while avoiding reduction in the efficiency of measurement preparation operations. 
     To achieve the aforesaid object, the brain function measurement apparatus according to one aspect of this invention comprises: a plurality of measurement probes which either apply measurement light to the head of a subject or receive measurement light from the head of the subject; a holder which is fitted to the head of the subject and comprises a plurality of probe attachment parts for attaching the plurality of measurement probes; a light blocking member which is arranged so as to cover the holder in a state where the plurality of measurement probes have been attached to the probe attachment parts, and blocks light from entering the plurality of measurement probes; and a contact prevention member which is arranged between the holder and the light blocking member and prevents the light blocking member from contacting the measurement probes. 
     In the brain function measurement apparatus according to this aspect of the invention, as described above, the brain function measurement apparatus is provided with a light blocking member which is arranged so as to cover the holder in a state where a plurality of measurement probes have been attached to the probe attachment parts, and blocks light from entering the plurality of measurement probes; and a contact prevention member which is arranged between the holder and the light blocking member and prevents the light blocking member from contacting the measurement probes. This makes it possible to prevent light other than measurement light from entering the measurement probes by means of the light blocking member. Furthermore, the contact prevention member prevents the light blocking member from contacting measurement probes on which adjustment operations have been performed, so even if a light blocking member is attached, the installation state of the measurement probes will not change, so repeated measurement probe adjustment operations can be avoided. Consequently, due to the fact that the installation state of the measurement probes does not change, measurement light from the measurement probes can be accurately applied to the head of the subject, and light other than measurement light can be prevented from entering the measurement probes while avoiding reduction in efficiency of measurement preparation operations. 
     The brain function measurement apparatus according to the above aspect is preferably configured such that the height of protrusion of the contact prevention member from the holder in the state where the contact prevention member has been arranged on the holder is greater than the height of protrusion of the measurement probes from the holder. Configuring the apparatus in this manner makes it possible to increase the distance between the light blocking member and the measurement probes by means of the contact prevention member, whereof the height of protrusion from the holder is relatively large, thus making it possible to more reliably prevent the light blocking member from contacting the measurement probes. 
     In the brain function measurement apparatus according to the above aspect, the contact prevention member preferably comprises dummy measurement probes which are removably attached to the probe attachment parts. If the apparatus is configured in this manner, there is no need to separately provide attachment parts for attaching the contact prevention member to the holder. Furthermore, configuring the dummy measurement probes to be removably installable in the probe attachment parts makes it possible to attach the dummy measurement probes to probe attachment parts corresponding to the optimal locations for attaching dummy measurement probes in accordance with the state of arrangement of measurement probes. 
     In this case, the total length of the dummy measurement probes is preferably made adjustable. Such a configuration allows the total length to be appropriately adjusted according to the location of arrangement of the dummy measurement probe such that the light blocking member will not contact the measurement probes, thus making it possible to more effectively prevent the light blocking member from contacting the measurement probes. 
     In the brain function measurement apparatus according to the above aspect, preferably, the light blocking member is formed as a flexible light blocking cloth, the light blocking cloth is arranged such that the edge of the light blocking cloth will fit tightly against the forehead of the subject upon tying a pair of string members connected to two ends of the light blocking cloth; and the contact prevention member is either arranged on the holder between the edge of the light blocking cloth and the measurement probes, or is arranged on the holder at a position adjacent to those measurement probes that are arranged toward the edge of the light blocking cloth. Here, when the light blocking member is formed as a light blocking cloth, it becomes possible to bring the edge of the light blocking cloth into tight contact with the forehead by tying two ends of the light blocking cloth with string members, in order to block light other than measurement light from entering the measurement probes from the direction of the subject&#39;s forehead. In this case, the closer to the edge of the light blocking cloth, the closer the light blocking cloth is arranged to the surface of the subject&#39;s forehead, so the light blocking cloth will more readily contact those measurement probes which are closer to the edge of the light blocking cloth. Noting this point, in the present invention, the contact prevention member is either arranged on the holder between the edge of the light blocking cloth and the measurement probes, or is arranged on the holder at a position adjacent to those of the plurality of measurement probes which are arranged toward the edge of the light blocking cloth. A contact prevention member arranged at a position as described above thus makes it possible to more effectively prevent the measurement probes which are relatively more prone to contacting the light blocking cloth from contacting the light blocking cloth. 
     In the brain function measurement apparatus according to the above aspect, preferably, the contact prevention member comprises a hair parting part for parting hair on the head of the subject. Designing the apparatus in this manner makes it possible to use the contact prevention member as a hair parting member, thereby eliminating the need to provide a member for hair parting separately from the contact prevention member. As a result, an increase in the number of parts of the brain function measurement apparatus can be avoided even though a contact prevention member is provided. 
     In this case, preferably, the contact prevention member comprises a light source part which emits light; and the hair parting part is designed to guide light from the light source part in the state where the contact prevention member is detached from the holder, thereby allowing the light from the light source part to be applied to the head of the subject. When hair on the subject&#39;s head is to be parted, designing the apparatus in this manner makes it possible to apply light from the light source to the area where hair is being parted. As a result, the efficiency of the operation of parting hair can be increased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a drawing schematically illustrating the overall configuration of a brain function measurement apparatus according to a first embodiment. 
         FIG. 2  is a block diagram illustrating the configuration of the brain function measurement apparatus according to a first embodiment. 
         FIG. 3  is an overall perspective view illustrating the state where measurement probes and dummy probes of the brain function measurement apparatus according to a first embodiment have been arranged in the holder. 
         FIG. 4  is a perspective view illustrating the configuration of the measurement probes and dummy probes of the brain function measurement apparatus according to a first embodiment. 
         FIG. 5  is a partial perspective view illustrating the state where the measurement probes and dummy probes of the brain function measurement apparatus according to a first embodiment have been arranged in the holder. 
         FIG. 6  is a drawing illustrating the light blocking cloth of the brain function measurement apparatus according to a first embodiment. 
         FIG. 7  is a drawing intended to explain the arrangement of measurement probes and dummy probes in the holder of the brain function measurement apparatus according to a first embodiment. 
         FIG. 8  is a partial perspective view illustrating the state where measurement probes and dummy probes of the brain function measurement apparatus according to a second embodiment have been arranged in the holder. 
         FIG. 9  is a drawing intended to explain the configuration of the hair parting part of a dummy probe of the brain function measurement apparatus according to a second embodiment. 
         FIG. 10  is a drawing intended to explain the arrangement of measurement probes and dummy probes in the holder of the brain function measurement apparatus according to a first modified example of the first embodiment. 
         FIG. 11  is a perspective view illustrating the configuration of a dummy probe according to a second modified example of the second embodiment. 
         FIG. 12  is a perspective view illustrating the configuration of a dummy probe of a brain function measurement apparatus according to a third modified example of the second embodiment. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Specific embodiments of the present invention will be described below based on the drawings. 
     First Embodiment 
     Overall Configuration of Brain Function Measurement Apparatus 
     First, the overall configuration of a brain function measurement apparatus  100  according to a first embodiment of the present invention will be described with reference to  FIGS. 1 through 7 . 
     As shown in  FIG. 1 , the brain function measurement apparatus  100  according to the first embodiment is an optical measurement device which non-invasively optically measures the brain activity of the subject P, and is configured as a brain function imaging device which visualizes the state of activity near the brain surface in real time based on functional near-infrared spectroscopy (fNIRS). Furthermore, the brain function measurement apparatus  100  comprises, for example, a portable main unit  1  which performs brain function measurement while being carried by the subject P, and a control unit  2  which receives the brain function measurement data generated by the main unit  1  via wireless communication and records this data. 
     Thus, with the brain function measurement apparatus  100  according to the first embodiment, the subject P is not constrained to being in the vicinity of the measurement apparatus (control unit  2 ) during brain function measurement and can move freely while carrying the main unit  1 , making it possible to perform brain function measurement in an environment closer to daily life. For example, with the brain function measurement apparatus  100  according to the first embodiment, it is possible to perform brain function measurement on a subject P whole is active outdoors and exposed to the sun, or to perform brain function measurement on a subject P who is moving indoors through an area where other measurement devices which emit light are installed. 
     As shown in  FIG. 1  and  FIG. 2 , the main unit  1  comprises a light output part  11 , light detection part  12 , a measurement control part  13 , a main control part  14 , a communication part  15  and a storage part  16  inside a case  10  of a portable size. Furthermore, the main unit  1  is provided with an operation panel  17  (see  FIG. 1 ) in a portion of the surface of the case  10 . 
     Furthermore, the main unit  1  comprises light sending probes  4   a  and light receiving probes  4   b,  connected via optical fibers  3 . Furthermore, the main unit  1  is designed to allow connection of multiple (for example, four) light sending probes  4   a  and multiple (for example, four) light receiving probes  4   b.  Furthermore, the main unit  1  can be carried by the subject P by securing to the waist or the like using a harness  10   a.  It will be noted that the light sending probes  4   a  and light receiving probes  4   b  are examples of “measurement probes” of the present invention. The light sending probes  4   a  and light receiving probes  4   b  will be referred to hereinafter as measurement probes  4  when their configurations are not being specially distinguished. 
     Furthermore, as shown in  FIG. 2 , the brain function measurement apparatus  100  comprises a holder  5 , which is fitted to the head of a subject P and comprises a plurality (for example, a number greater than the number of measurement probes  4 ) of attachment parts  51  for attaching light sending probes  4   a  and light receiving probes  4   b.  The light sending probes  4   a  and light receiving probes  4   b  are arranged on the surface of the head of the subject P by attaching to the holder  5  which has been fitted to the head of the subject P. It will be noted that attachment units  51  are an example of the “probe attachment units” referred to in the patent claims. 
     Furthermore, as shown in  FIG. 3 , in the first embodiment, the brain function measurement apparatus  100  comprises a light blocking cloth  6 . The light blocking cloth  6  is arranged so as to cover the holder  5  in a state where measurement probes  4  have been attached to attachment parts  51 , and is designed to block light from entering the measurement probes  4 . Namely, the light blocking cloth  6  makes it possible to prevent sunlight from entering the measurement probes  4  even when the brain function measurement apparatus  100  is used outdoors. It will be noted that the light blocking cloth  6  is an example of the “light blocking member” referred to in the patent claims. 
     Furthermore, in the first embodiment, the brain function measurement apparatus  100  comprises dummy probes  7 . The dummy probes  7  are arranged between the holder  5  and the light blocking cloth  6  and are designed to prevent the light blocking cloth  6  from contacting the measurement probes  4 . It will be noted that the dummy probes  7  are an example of the “contact prevention member” and “dummy measurement probes” referred to in the patent claims. 
     Furthermore, the light sending probes  4   a  are designed to apply measurement light to the head of the subject P when arranged in the holder  5 . Moreover, the light receiving probes  4   b  are designed to receive measurement light from the head of the subject P when arranged in the holder  5 . Namely, the main unit  1  is designed to emit measurement light in the near-infrared wavelength range through the light sending probes  4   a  and detect measurement light which has been reflected or scattered from inside the head of the subject P by allowing it to enter into the light receiving probes  4   b,  thereby acquiring the intensity (received amount) of measurement light. 
     In particular, as shown in  FIG. 2 , the light output part  11  is designed to output measurement light to the light sending probes  4   a  via optical fibers  3 . The light output part  11  comprises, for example, a semiconductor laser or light emitting diode, and is designed to allow output of measurement light of multiple wavelengths (for example, measurement light of three wavelengths—780 nm, 805 nm and 830 nm) in the high bio-penetration near-infrared wavelength region. The light detection part  12  comprises, for example, a photomultiplier tube or photodiode, and is designed to acquire and detect, through optical fiber  3 , measurement light which has entered a light receiving probe  4   b.  The light detection part  12  outputs an electrical signal corresponding to the detected measurement light. 
     The main unit  1  is furthermore designed to acquire changes in hemoglobin levels (oxygenated hemoglobin, deoxygenated hemoglobin and total hemoglobin) during brain activity based on the intensity of the acquired measurement light. The brain function measurement apparatus  100  can thereby non-invasively acquire changes in hemoglobin levels during brain activity, namely, changes in blood flow rate and the state of activation of oxygen metabolism. Furthermore, the apparatus is designed to acquire two-dimensional distributions, with optical measurement being performed to measure brain activity at each measurement point (measurement channel), consisting of a pair of light sending probe  4   a  and light receiving probe  4   b.    
     Moreover, the measurement control part  13  controls the operation of light output part  11  and light detection part  12  in accordance with measurement conditions set by main control part  14 , and measurement parameters relating to output intensity of measurement light, detection sensitivity of light detection part  12 , etc. The main control part  14  is a computer comprising a CPU, memory, etc., which controls the measurement control part  13 , communication part  15  and storage part  16  by executing a measurement program stored in storage part  16 , to perform measurement operations, computation of measurement data based on obtained received light amount signals, and transmission of measurement data to the control unit  2 . Furthermore, the main control part  14  is designed to receive input operations from the subject P via the operation panel  17 . 
     The communication part  15  comprises a wireless communication module and enables bidirectional wireless communication with communication part  23  of control unit  2 , described below. The storage part  16  comprises, for example, nonvolatile memory, and stores measurement conditions and programs to be executed by main control part  14 . 
     Next, as shown in  FIG. 2 , the control unit  2  is a computer (PC) comprising a control part  21  consisting of a CPU, memory, etc., a storage part  22  consisting of an HDD, etc., and a communication part  23  consisting of a wireless communication module (or externally connected wireless communication unit), which computer functions as the control unit  2  of the brain function measurement apparatus  100  through execution by the control part  21  of a measurement program stored in the storage part  22 . Furthermore, the control unit  2  comprises a display part  24  consisting of a liquid crystal display, etc., and an operation input part  25  consisting of a keyboard and mouse, etc. 
     Configuration of Measurement Probes 
     As shown in  FIG. 4 , the measurement probe  4  is formed, for example, so as to have a cylindrical shape. The measurement probe  4  comprises a fiber head part  41 , probe main body part  42  and grip part  43 . Furthermore, the measurement probe  4  has a total length L 1 . The total length L 1  is assumed to signify the distance from the lower end face of the fiber head part  41  (the end face in the direction of arrow Z 2 ) to the upper end part  43   a  of the grip part  43 . 
     Furthermore, as shown in  FIG. 5 , the measurement probe  4  is designed to extend in a direction (arrow Z 1  direction) substantially perpendicular to the holder  5  (head) when arranged in a mounting part  51  of the holder  5 . The measurement probe  4  has a protrusion height h 1  from the holder  5 . The protrusion height h 1  is assumed to signify the distance from the upper end face of the attachment part  51  (the end face in the arrow Z 1  direction) to the upper end part  43   a  (the end face in the arrow Z 1  direction) of the grip part  43  of the measurement probe  4 . 
     The fiber head part  41  is arranged more towards the subject&#39;s head (in the arrow Z 2  direction) than the attachment part  51  in the state where the measurement probe  4  has been arranged in an attachment part  51  of the holder  5 . Furthermore, the fiber head part  41  is designed to retain an optical fiber  3  in a state with the end part  31  of the optical fiber  3  exposed. The end part  31  is designed to allow the output or input of measurement light. 
     Optical fiber  3  is furthermore inserted inside the probe main body part  42 . Furthermore, as shown in  FIG. 4 , the probe main body part  42  is provided with an engagement part  42   a  capable of engaging with an attachment part  51  of the holder  5 . Specifically, the engagement part  42   a  is formed as a convex part capable of fitting into the concave part of engagement part  51   a  of attachment part  51 . 
     Grip part  43  is provided on the side of the measurement probe  4  in the arrow Z 1  direction. The surface of the side face  43   b  of the grip part  43  is, for example, knurled. Furthermore, the optical fiber  3  is arranged inside the measurement probe  4  via the side face  43   b  of the grip part  43 . Namely, the measurement probe  4  is configured as an L-shaped attachment member (attachment). Furthermore, the grip part  43  has a length L 2  in the Z axis direction and has a diameter d 1  when viewed from the direction of arrow Z 1 . 
     Configuration of Dummy Probe 
     As shown in  FIG. 4 , the dummy probe  7  has an outer shape similar to measurement probe  4 . Specifically, the dummy probe  7  has a cylindrical shape and comprises a probe main body part  71  and grip part  72 . For example, the total length L 11  of the dummy probe  7  is greater than the total length L 1  of the measurement probe  4  in the direction (Z axis direction) perpendicular to the plane (head surface) in which the holder  5  is arranged. It will be noted that total length L 11  is assumed to signify the distance from the lower end (the end in the arrow Z 2  direction) of the probe main body part  71  to the upper end  72   a  (the end in the arrow Z 1  direction) of the grip part  72 . 
     The probe main body part  71  has the same shape as the probe main body part  42  of a measurement probe  4 . However, unlike the probe main body part  42  of a measurement probe  4 , the probe main body part  71  does not have an optical fiber  3  inserted into it. Furthermore, the grip part  72  is knurled similarly to the grip part  43  of a measurement probe  4 . Moreover, the grip part  72  has a length L 12  in the Z axis direction. For example, the length L 12  of the grip part  72  is made equal to or greater than the length L 2  of the grip part  43  of a measurement probe  4 . It will be noted that in  FIG. 4 , length L 12  is illustrated as being greater than length L 2 . 
     Here, in the first embodiment, the total length L 11  of the dummy probe  7  is made adjustable. Namely, the total length L 11  of the dummy probe  7  is made adjustable by changing the magnitude of the aforementioned length L 12  of the grip part  72  (for example, by replacing with a grip part  72  of a different length). Therefore, the relative size relationship between the total length L 11  of the dummy probe  7  and the length L 12  of the grip part  72  on the one hand and the total length L 1  of the measurement probe  4  and the length L 2  of the grip part  43  on the other, is not limited to that illustrated in  FIG. 4 . For example, depending on the position of arrangement of the dummy probe  7 , total length L 11  may be smaller than total length L 1 . 
     Furthermore, the diameter d 2  of the dummy probe  7  (grip part  72 ) when viewed from the arrow Z 1  direction is equal to or greater than the diameter d 1  of measurement probe  4  (grip part  43 ). It will be noted that in the example of  FIG. 4 , the diameter d 2  of the grip part  72  is shown as having approximately the same size as diameter d 1  of grip part  43 . 
     Furthermore, in the first embodiment, the dummy probe  7  is designed to be installable in and removable from mounting part  51 . Specifically, the probe main body part  71  of dummy probe  7  is provided with an engagement part  71   a.  The engagement part  71   a  is designed to have the same structure as engagement part  42   a  of measurement probe  4 . 
     Furthermore, as shown in  FIG. 5 , the dummy probe  7  is designed to extend in a direction (arrow Z 1  direction) substantially perpendicular to the holder  5  (head) when arranged in the holder  5 . Furthermore, the dummy probe  7  has a protrusion height h 2  from the holder  5 . Here, in the first embodiment, the protrusion height h 2  of the dummy probe  7  is greater than the protrusion height hl of measurement probe  4 . It will be noted that protrusion height h 2  is used to signify the distance from the upper end face of attachment part  51  to the upper end  72   a  of grip part  72 . 
     As a result, when the light blocking cloth  6  is arranged in a state where measurement probes  4  and dummy probes  7  have been arranged in the holder  5  as shown in  FIG. 3 , the upper end  72   a  of the grip part  72  of the dummy probes  7  (the end face in the arrow Z 2  direction) contacts the surface of the light blocking cloth  6  on the holder  5  side. As a result, a separation distance D 10  greater than protrusion height hl is formed between the light blocking cloth  6  and the holder  5 , preventing the light blocking cloth  6  from contacting the upper end  43   a  of the grip part  43  of the measurement probes  4 . 
     Configuration of Light Blocking Cloth 
     As shown in  FIG. 6 , in the first embodiment, the light blocking cloth  6  is made to have flexibility. Specifically, the light blocking cloth  6  is made from a material which blocks light, so as to block infrared light in particular. Consequently, the light blocking cloth  6  elastically deforms according to the state of arrangement of the dummy probes  7  and measurement probes  4  arranged in the holder  5 , and can thus prevent external light (sunlight, etc.) from penetrating to the holder  5  side. 
     In particular, a string insertion part  61  is provided in edge  6   a  of light blocking cloth  6 . A string member  62  is then inserted into the string insertion part  61 . The two ends of the string member  62  are then pulled out through the two openings  61   a  of the string insertion part  61  provided at two ends of the light blocking cloth  6 . The portion of the string member  62  which has been pulled out from one opening  61   a  and the portion of string member  62  which has been pulled out from the other opening  61   a  are then tied to each other. 
     Furthermore, the length of the edge  6   a  of the light blocking cloth  6  corresponds to the length of the portion of the string member  62  that has been inserted into and is inside the string insertion part  61 . 
     Namely, the light blocking cloth  6  is designed such that the edge  6   a  of the light blocking cloth  6  can be shortened up by pulling the string member  62  out from the two openings  61   a.    
     As shown in  FIG. 3 , the light blocking cloth  6  is put on so as to cover the entirety of the holder  5  in the state where the holder  5  has been fitted to the head of a subject P and measurement probes  4  and dummy probes  7  have been arranged in the holder  5 . Furthermore, by pulling out and tying the pair of string members  62  connected to the openings  61   a  provided at two ends of the light blocking cloth  6 , the light blocking cloth  6  is tightened up and arranged such that the edge  6   a  of the light blocking cloth  6  fits tightly against the forehead Pa of the subject P. In this way, the gap between the forehead Pa of the subject P and light blocking cloth  6  can be made smaller, making it possible to prevent entry of light toward the holder  5  through this gap. Furthermore, the fact that the light blocking cloth  6  has flexibility and that its edge  6   a  can be shortened makes it possible to suitably prevent the entry of light for subjects P with different sizes of the head and face. 
     Furthermore, when the holder  5  side surface of the light blocking cloth  6  contacts the dummy probes  7 , a separation distance D 10  corresponding to the protrusion height h 2  of the dummy probes  7  is formed. Namely, the light blocking cloth  6  and measurement probes  4  do not come into contact in areas where the separation distance D 10  is greater than the protrusion height hl of the measurement probes  4 . It will be noted that in  FIG. 3 , all of the measurement probes  4  which have been arranged in the holder  5  are arranged in a state separated from (not in contact with) the light blocking cloth  6 . 
     Configuration of Holder 
     As shown in  FIG. 3  and  FIG. 7 , the holder  5  is provided with numerous attachment parts  51  disposed in an array at a substantially equal spacing D 20 , and has a curved surface shape matching the shape of a head. Furthermore, the attachment parts  51  are connected to each other by means of band-shaped connecting parts  52 . The connecting parts  52  are made from resin or the like, and have flexibility in the direction perpendicular to the head. It will be noted that the holder  5  shown in  FIG. 3  is of a whole head type, which allows measurement probes  4  to be arranged over the entire head, and is formed in the shape of a helmet that covers the entire brain function measurement region of the head. Furthermore, the holder  5  is fastened to the head of the subject P using fastening belts (not illustrated) or the like. 
     The user determines the arrangement of measurement probes  4  in the attachments parts  51  (the measurement region R 1 ) in accordance with the area (frontal, parietal, temporal, whole head, etc.) that the user wishes to measure, and attaches the measurement probes  4  to the holder  5 . For example, as shown in  FIG. 7 , when attaching the measurement probes  4 , the light sending probes  4   a  and light receiving probes  4   b  may be arranged in the respective attachment parts  51  so as to alternate in both the row and column directions. Measurement channels (measurement points) are thereby formed between adjacent light sending probes  4   a  and light receiving probes  4   b.    
     In particular, as shown in  FIG. 3 , the attachment parts  51  have a hole  51   a  matching the shape of a measurement probe  4 . The holder  5  is designed to allow one measurement probe  4  to be inserted into the opening  51   a  of each attachment part  51  and fastened therein. Specifically, as shown in  FIG. 5 , in the hole  51   a,  there is provided an engagement part  51   b  capable of engaging with the engagement part  42   a  of a measurement probe  4  or the engagement part  71   a  of a dummy probe  7 . In particular, engagement part  51   b  is formed as a concave part provided in the hole  51   a,  and is configured so as to mate with engagement parts  42   a  and  71   a,  which are formed as convex parts. 
       FIG. 7  shows an example of the arrangement of measurement probes  4  and dummy probes  7  in the holder  5  according to the first embodiment. As shown in  FIG. 7 , looking from the arrow Z 1  direction, light sending probes  4   a  have been arranged in a plurality of attachment parts  51  (the attachment parts  51  labeled “A 1 ”). Light receiving probes  4   b  are arranged in a plurality of attachment parts  51  (the attachment parts  51  labeled “A 2 ”). Furthermore, dummy probes  7  are arranged in a plurality of attachment parts  51  (the attachment parts  51  labeled “B”). 
     Namely, in the first embodiment, some of the dummy probes  7  are arranged in the holder  5  between the edge  6   a  of the light blocking cloth  6  and the measurement probes  4 . Furthermore, in the direction along the Y axis (the direction going from the occipital region toward the frontal), dummy probes  7  are arranged on both sides of the measurement probes  4  (measurement region R 1 ). Namely, dummy probes  7  are arranged in attachment parts  51  both on the side of edge  6   a  of light blocking cloth  6  (the side in the direction of arrow Y 2 ) in the measurement region R 1  formed by measurement probes  4 , and on the side opposite to edge  6   a  of light blocking cloth  6  (the side in the direction of arrow Y 1 ) in the measurement region R 1 . 
     The light blocking cloth  6  is thus lifted in the arrow Z 1  direction by dummy probes  7  arranged both on the side of edge  6   a  of light blocking cloth  6  in the measurement region R 1  and on the side opposite to edge  6   a  of light blocking cloth  6 , and a separation distance D 10  from the holder  5  is formed in the measurement region R 1 . 
     Furthermore, dummy probes  7  are attached to attachment parts  51  adjacent to the attachment parts  51  to which measurement probes  4  have been attached. This makes it possible to make the separation distance D 10  formed in the measurement region R 1  relatively large. 
     Effect of the First Embodiment 
     The first embodiment allows the followings effects to be obtained. 
     In the first embodiment, as described above, the brain function measurement apparatus  100  is provided with a light blocking cloth  6  which is arranged so as to cover the holder  5  and block light from entering into the measurement probes  4  in the state where multiple measurement probes  4  have been attached to attachment parts  51 ; and dummy probes  7  which are arranged between the holder  5  and the light blocking cloth  6  and prevent the light blocking cloth  6  from contacting the measurement probes  4 . This makes it possible to prevent light other than measurement light from entering the measurement probes  4  (light receiving probes  4   b ) by means of the light blocking cloth  6 . Furthermore, the dummy probes  7  prevent the light blocking cloth  6  from contacting measurement probes  4  on which adjustment operations have been performed, so even if a light blocking cloth  6  is attached, the installation state of the measurement probes  4  will not change, so repeated adjustment operations on the measurement probes  4  can be avoided. As a result, because the installation state of measurement probes  4  does not change, measurement light from the measurement probes  4  can be applied accurately to the head of the subject P, and light other than measurement light can be prevented from entering the measurement probes  4  while avoiding reduction in the efficiency of measurement preparation operations. 
     Furthermore, in the first embodiment, as described above, the protrusion height h 2  of dummy probes  7  from the holder  5  is designed to be greater than the protrusion height hl of measurement probes  4  from the holder  5  in the state where dummy probes  7  have been arranged in the holder  5 . Thus, the distance between the light blocking cloth  6  and the measurement probes  4  can be increased by means of the dummy probes  7 , whereof the protrusion height h 2  from the holder  5  is relatively large, thus making it possible to more reliably prevent the light blocking cloth  6  from contacting the measurement probes  4 . 
     Furthermore, the first embodiment, as described above, is designed to allow dummy probes  7  to be removably attached to attachment parts  51 . Thus, there is no need to provide separate attachment parts for dummy probes  7  in order to attach dummy probes  7  to the holder  5 . Furthermore, configuring the dummy probes  7  to be removably installable in attachment parts  51  makes it possible to attach the dummy probes  7  to attachment parts  51  corresponding to the optimal locations for attaching dummy probes  7  (for example, attachment parts  51  “B” in  FIG. 7 ) in accordance with the state of arrangement of measurement probes  4 . 
     Furthermore, in the first embodiment, as described above, the total length L 11  of a dummy probe  7  is made greater than the total length L 1  of a measurement probe. It is also adjustable. This allows the total length to be appropriately adjusted according to the location of arrangement of the dummy probe  7  such that the light blocking cloth  6  will not contact the measurement probes  4 , thus making it possible to more effectively prevent the light blocking cloth  6  from contacting the measurement probes  4 . Furthermore, if the total length L 11  is made greater than that of the measurement probes  4 , the protrusion height h 2  of dummy probes  7  from the holder  5  can be easily made greater than the protrusion height hl of measurement probes  4  from the holder  5  by attaching dummy probes  7 , which have a relatively large total length L 11 , to attachment parts  51 . 
     Furthermore, in the first embodiment, as described above, the light blocking cloth  6  is formed to have flexibility and the light blocking cloth  6  is arranged such that the edge  6   a  of the light blocking cloth  6  fits tightly against the forehead Pa of the subject P by tying a pair of string members  62  connected to openings  61   a  at two ends of the light blocking cloth  6 . Furthermore, dummy probes  7  are arranged on the holder  5  between the edge  6   a  of the light blocking cloth  6  and the measurement probes  4 . Here, it is possible to bring the edge  6   a  of the light blocking cloth  6  into tight contact with the forehead Pa by tying two ends of the light blocking cloth  6 , in order to block light other than measurement light from entering the measurement probes  4  from the direction of the forehead Pa of the subject P (arrow Y 1  direction). 
     In this case, the closer to the edge  6   a  of the light blocking cloth  6 , the closer the light blocking cloth  6  is arranged to the surface of the forehead Pa of the subject P, so those measurement probes  4  which are closer to the edge  6   a  of the light blocking cloth  6  will more readily contact the light blocking cloth  6 . On this point, by configuring as described above, it becomes possible to effectively prevent the measurement probes  4  which are relatively more prone to contacting the light blocking cloth  6  from contacting the light blocking cloth  6  by means of dummy probes  7  arranged at the positions described above. 
     Second Embodiment 
     Next, the configuration of a brain function measurement apparatus  200  of a second embodiment will be described with reference to  FIG. 8  and  FIG. 9 . In the brain function measurement apparatus  200  according to the second embodiment, the dummy probes  207  are provided with a hair parting part  273  for parting hair Pb on the head of the subject P. It will be noted that components which are the same as in the first embodiment described above will be assigned the same reference symbols in the drawings, and description thereof will be omitted. (Configuration of brain function measurement apparatus according to a second embodiment) 
     The brain function measurement apparatus  200  according to the second embodiment of the present invention comprises dummy probes  207  as shown in  FIG. 8 . A dummy probe  207  comprises a probe main body part  271 , grip part  272 , and hair parting part  273 . 
     The probe main body part  271 , in addition to having the configuration of probe main body part  71  of dummy probe  7  according to the first embodiment, is also provided with a switching part  274  on its side face. The grip party  272  is made substantially identical to the grip part  43  of a measurement probe  4 . 
     Here, as shown in  FIG. 9 , in the second embodiment, the hair parting part  273  is designed to allow parting the hair Pb on the head of the subject P. Specifically, the hair parting part  273  is formed in the shape of a rod protruding from the grip part  272 , and has a bowl-shaped tip. Namely, the hair parting part  273  has the same sort of shape as a so-called ear pick member. Furthermore, the diameter d 12  of the hair parting part  273  is smaller than the diameter d 11  of the hole  51   a  of an attachment part  51 . Consequently, hair Pb can be parted by moving the hair parting part  273  inside the hole  51   a  of an attachment part  51 . 
     Furthermore, in the second embodiment, dummy probe  7  comprises a light source part  275  which emits visible light VL (for example, white, green, etc.). Furthermore, the light source part  275  comprises, for example, a light emitting diode. Furthermore, dummy probe  7  comprises a battery  276  which supplies power to the light source part  275 . Furthermore, switching part  274  is configured to switch between a state in which power is supplied from battery  276  to light source part  275 , and a state in which power is not supplied from battery  276  to light source part  275 . For example, the switching part  274  may be configured to switch between a state in which the battery  276  and light source part  275  are connected and a state in which they are not connected by being moved in the Z axis direction. 
     Furthermore, in the second embodiment, the hair parting part  273  of dummy probe  207  is designed to allow visible light VL to be applied from light source part  275  to the head of the subject P by guiding visible light VL from the light source part  275  in the state where the dummy probe  207  has been detached from the holder  5 . Specifically, as shown in  FIG. 9 , the hair parting part  273  is fashioned, for example, from a member made entirely of resin or rubber and having a transparent color (having visible light transmittance). It will be noted that when the hair parting part  273  is fashioned from an elastically deformable material such as rubber, even if it should contact the head (scalp), injury to the scalp can be avoided. 
     Furthermore, as shown in  FIG. 8 , the dummy probe  207  according to the second embodiment, just as the dummy probe  7  according to the first embodiment, has a protrusion height h 3  greater than the protrusion height hl of measurement probes  4  from the holder  5 . 
     The rest of the configuration of the second embodiment is the same as in the first embodiment described above. 
     Effect of the Second Embodiment 
     The second embodiment allows the followings effects to be obtained. 
     In the second embodiment, as described above, the dummy probes  207  are provided with a hair parting part  273  for parting hair Pb on the head of the subject P. A dummy probe  207  can thus be used as a hair parting member, eliminating the need to provide a member for hair parting separately from the dummy probe  207 . As a result, an increase in the number of parts of the brain function measurement apparatus  200  can be avoided even though a dummy probe  207  is provided. 
     Furthermore, in the second embodiment, as described above, the dummy probe  207  is provided with a light source part  275  which emits light (visible light VL). Furthermore, the hair parting part  273  is designed to guide light from the light source part  275  in the state where the dummy probe  207  has been detached from the holder  5 , so as to allow light from the light source part  275  to be applied to the head of the subject P. When hair Pb on the head of a subject P is to be parted, this makes it possible to apply light from the light source part  275  to the area where hair is being parted. As a result, the efficiency of the operation of parting hair Pb can be increased. 
     The rest of the effects of the second embodiment are the same as in the first embodiment described above. 
     Modified Examples 
     It should be noted that the embodiments disclosed here should be seen as being in all respects illustrative and not limitative. The scope of the present invention is indicated by the scope of patent claims and not by the foregoing description of embodiments, and includes all modifications (modified example) that are of equivalent meaning to and within the scope of the patent claims. 
     For example, in the first embodiment and second embodiment described above, an example was presented in which the brain function measurement apparatus was provided with a portable main unit for performing brain function measurement while being carried by the subject, but the present invention is not limited to this. For example, the present invention can also be configured as a brain function measurement apparatus provided with a stationary main unit. 
     Furthermore, in the first embodiment and second embodiment described above, an example was presented in which the protrusion height (h 2  or h 3 ) of the dummy probes was made greater than the protrusion height h 1  of the measurement probes, but the invention is not limited to this. Namely, in the present invention, the protrusion height (h 2  or h 3 ) of the dummy probes may also be made less than or equal to the protrusion height hl of the measurement probes, so long as the light blocking cloth can be prevented from contacting the measurement probes by means of the dummy probes. 
     Furthermore, in the first embodiment and second embodiment described above, an example was presented in which dummy probes were made installable in and removable from attachment parts in which measurement probes are installed and removed from, but the present invention is not limited to this. For example, in the present invention, dedicated attachments parts for dummy probes only may also be provided in the holder, or dummy probes (contact prevention members) may be integrally provided in the holder. 
     Furthermore, in the first embodiment and second embodiment described above, an example was presented in which the total length L 11  of a dummy probe was made greater than the total length L 1  of a measurement probe, but the invention is not limited to this. Namely, in the present invention, the total length L 11  of a dummy probe may also be made less than or equal to the total length L 1  of a measurement probe, so long as the light blocking cloth can be prevented from contacting the measurement probes by means of the dummy probes. 
     Furthermore, in the first embodiment and second embodiment described above, an example was presented in which a light blocking cloth was configured as the light blocking member, but the present invention is not limited to this. For example, a cap having light block characteristics (light blocking cap) may also be configured as the light blocking member. 
     Furthermore, in the first embodiment and second embodiment described above, an example was presented in which dummy probes were arranged between the edge of the light blocking cloth and the measurement probes on the holder, but the invention is not limited to this. For example, as shown for the brain function measurement apparatus  300  based on the modified example illustrated in  FIG. 10 , dummy probes  7  may be arranged on the holder  5  at positions (the attachment parts  51  at the positions indicated by “B” in  FIG. 10 ) adjacent to the measurement probes  4  (the measurement probes  4  arranged at the positions indicated by “A” in  FIG. 10 ) arranged toward the edge  6   a  of the light blocking cloth  6 . Based on the position of arrangement of these dummy probes  7 , the light blocking cloth  6  can be effectively prevented from contacting the measurement probes  4  arranged in the measurement region R 2 . 
     Furthermore, in the embodiment described above, an example was presented in which the hair parting part was formed having a shape similar to an ear pick member, but the present invention is not limited to this. For example, as shown in  FIG. 11 , the hair parting part  473  of the dummy probe  407  may also be formed to have rod shape with a sphere formed on its end. 
     Furthermore, in the embodiment described above, an example was presented in which the light source part was made from a light emitting diode, but the invention is not limited to this. For example, in the present invention, the light source part may also be made from a light bulb or from a laser diode. 
     Furthermore, in the embodiment described above, an example was presented in which the dummy probe was designed to have a fixed total length, but the present invention is not limited to this. For example, it may be made variable between total length L 21  and total length L 22 , as shown for the dummy probe  507  of the third modified example illustrated in  FIG. 12 . For example, the dummy probe  507  according to the third modified example comprises a hair parting part  573 . The dummy probe  507  is designed to have a total length of L 21  when the hair parting part  573  has been retracted and a total length of L 22  when the hair parting part  573  has been extended.