Abstract:
The present invention relates to a device for inserting a brain electrode which makes it easy to install the device and to insert the brain electrode and yet allows the electrode to be inserted with sufficient precision. The present invention is a brain electrode securing device, in which an electrode-wire-type electrode held by an electrode holder is inserted into the brain through a hole formed in the skull for the purpose of measuring changes in electrical potential at an electrode at a measuring location inside the brain, and the device comprises a casing which is securely mounted on the skull so as to surround the aforementioned hole, an electrode holder which is arranged so as to slide freely in relation to the aforementioned casing, and a screw rod which is screwed approximately to the center of the electrode holder and is supported so as to rotate freely in relation to the aforementioned casing.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is a brain electrode securing device, and particularly to a brain electrode securing device which holds an electrode inserted into the brain in order to measure changes in electrical potential in the nerve cells in the brains of small animals such as mice and rats and to stimulate the aforementioned brain nerve cells electrically. 
     2. Description of the Related Art 
     In order to measure changes in electrical potential in the nerve cells in the brains of small animals such as mice and rats and to stimulate the aforementioned brain nerve cells electrically, it is necessary to open a hole in the skull of the small animal and to insert an electrode through the aforementioned hole as far as a prescribed location inside the brain. This electrode is secured to the skull by means of a brain electrode securing device. 
     A brain electrode securing device of this type as shown in FIG. 8 was provided. In this brain electrode securing device, two screw rods  2 , 2  were screwed into the electrode holder  1  and the lower ends of the screw rods  2 , 2  were arranged with the hole a opened in the skull interposed between them and the lower ends of the aforementioned screw rods  2 , 2  were rotatably secured, by means of dental cement  3  etc., to the hole a opened in the skull A. Furthermore, in this brain electrode securing device, the connector casing  4  is mounted on the skull A so as to surround the screw rods  2 , 2 , this connector casing  4  is secured to the skull A by means of dental cement  3  or the like, and the connector  6  is installed in the aforementioned connector casing  4  and the upper end of the electrode wire  5  is connected to the connector  6  using the lead  7 . In such a brain electrode securing device, the electrode holder  1  is lowered by rotating the screw rods  2 , 2 , and the tip (the electrode)  5   a  of the electrode wire  5  is Inserted to the prescribed position inside the brain. 
     However, in the aforementioned brain electrode securing device, it is necessary to arrange the electrode wire  5  perpendicularly in relation to the skull A and, because of this, the operation to install the two screw rods  2 , 2 , in which the 2 screw rods  2 , 2  have to be secured in relation to the surface of the skull while their position is adjusted individually in a perpendicular direction, is laborious. 
     Furthermore, with the brain electrode securing device, a laborious operation is required in which, after the screw rods  2 , 2  have been secured, the connector casing  4  has to be fixed on the skull A, the aforementioned connector casing has to be secured and then the electrode wire  5  has to be connected using the lead  7 . 
     In addition, in the aforementioned brain electrode securing device, when the electrode  5   a  is being inserted into the brain, not only is it necessary to perform a laborious operation in which the electrode holder  1  is lowered by making each of the  2  screw rods rotate slightly in relation to one another, while this operation is being performed the electrode holder  1  shakes as it is lowered so that the electrode  5  which is held in the aforementioned electrode holder  1  sways from side to side and it is difficult to perform the insertion with adequate precision. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a brain electrode securing device in which the operation to install the device for securing the brain electrode and the operation to insert the electrode are easy and yet the electrode can be inserted with sufficient precision. 
     The present invention aimed at achieving the aforementioned object is a brain electrode securing device, in which an electrode-wire-type electrode held by an electrode holder is inserted into the brain through a hole formed in the skull in order to measure changes in electrical potential at an electrode at a measuring location inside the brain, comprising: 
     a casing which is fixedly mounted on the skull so as to surround the aforementioned hole; 
     an electrode holder which is arranged so as to slide freely in relation to the aforementioned casing; and 
     a screw rod which is screwed approximately to the center part of the electrode holder and is supported so as to rotate freely in relation to the aforementioned casing. 
     Furthermore, the brain electrode securing device according to the present invention is characterized in that a connector is secured to the casing and one end of a flexible baseboard is secured to the aforementioned electrode holder, one end of the wire of the aforementioned flexible baseboard is connected to the aforementioned connector and the other end of the wire of the aforementioned flexible baseboard is connected to the upper end of the aforementioned electrode wire. 
     In the brain electrode securing device according to the present invention, the electrode holder and the connector are assembled integrally in the casing. Therefore, installation operation can be completed only by mounting the casing on the skull so that the tip (the electrode) of the electrode wire fits into the hole in the skull and by securing the aforementioned casing to the skull by means of dental cement or the like. 
     To be precise, in the brain electrode securing device according to the invention, it is possible to ensure the screw rods are perpendicular by mounting the casing in the skull without taking into account the perpendicularity of the screw rods (perpendicularity of the electrode wire), but the electrode wire and the connector can be connected in advance so that the installation operation becomes simple. 
     In addition, the brain electrode securing device according to the present invention is characterized in that the casing of the device is of watertight construction and the aforementioned casing can be secured to the skull in a watertight fashion. 
     In the brain electrode securing device according to the invention, the casing is of watertight construction so that the underwater behavior of small animals can be assessed and yet, because no special cover is required, the device is compact and the mounting operation is easy. 
     The casing can be secured to the skull with a publicly known watertight construction and using publicly known materials which can be secured in a watertight fashion. For example, it is possible to use the dental cement employed in the prior art to secure the brain electrode securing device. However, in this case it is preferable to coat the outer surface of the dental cement with waterproof material. 
     In addition, the brain electrode securing device according to the present invention is characterized in that the casing is divided into upper and lower parts, the lower part of the casing is secured to the aforementioned skull and the upper part of he casing is connected to the aforementioned lower part of the casing. 
     In this brain electrode securing device according to the present invention, when it is desired to temporarily interrupt the measurement process, by detaching the upper part of the casing from the lower part of the casing it is possible to remove the main part of the device from the small animal so that the burden on it is relieved during periods when measurement is not being carried out. 
     The lower part of the casing can be secured to the upper part of the casing using publicly known connection means which can be connected in a watertight fashion. 
     Furthermore, the brain electrode securing device according to the present invention comprises a cover which is coupled to the upper portion of the aforementioned lower part of the casing and covers the opening in the upper portion of the aforementioned lower part of the casing. 
     In the brain electrode securing device, when the upper part of the casing is removed from the lower part of the casing the cover seals off the opening in the lower part of the casing and dirt and the like is prevented from entering the brain. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a general perspective view showing the main parts of the interior of an embodiment of the brain electrode securing device according to the invention; 
     FIG. 2 is a section through the brain electrode securing device shown in FIG. 1, when it is installed on a skull; 
     FIG. 3 is a different section through the brain electrode securing device shown in FIG. 1; 
     FIG. 4 is a section through another embodiment of the brain electrode securing device according to the present invention, when it is installed in the skull; 
     FIG. 5 is a general perspective view of a further embodiment of the brain electrode securing device according to the invention; 
     FIG. 6 is a section through the brain electrode securing device shown in FIG. 5, when it is installed in the skull; 
     FIG. 7 shows a section through the brain electrode securing device when the device body is removed from its base and the base is covered by the cover; 
     FIG. 8 is a general view showing the device for securing the brain electrode provided above. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the brain electrode securing device  10  as shown in FIGS. 1 to  3  the horizontal sectional face has a rectangular casing  11  which is made of transparent material. The socket  12   a  of the connector  12  is securely installed in the outer face of this casing  11  and the electrode holder  13  in arranged in the interior so as to be capable of sliding in the upward and downward directions. In the electrode holder  13 , cutouts  13   a ,  13   b  and  13   c  are formed in the center of the upper part and in pairs of side faces lying opposite one another, and a female screw hole  13   d  extends from the center of the upper face to the center of the lower face, and furthermore the upper ends of guide tubes  14  extending in the downward direction are secured to the cutouts  13   b . The electrode wire  15  is inserted into the guide tube  14 . 
     The screw rod  16  is screwed into the female screw hole  13   d  of the aforementioned electrode holder  13 , and the lower end and the upper part of the aforementioned screw rod  16  is supported so as to be freely rotatable in the plates  17 , 18  which are installed along the full width of the inside of the casing  11 . Engagement means  16   a  which engage with a tool, such as a spanner, for turning the aforementioned screw rod  16  is formed in the end of this screw rod  16 . 
     In addition, a flexible baseboard is arranged in the cutouts  13   a ,  13   c  in the electrode holder  13 . The end of the aforementioned flexible baseboard  19  extends as far as the socket  12   a  of the connector  12  through the hole  11   a  formed in the side wall of the casing  11 , and one end of the wire  19   a  of this flexible baseboard  19  is connected to the socket  12   a  of the connector  12 . The other end of the wire  19   a  is connected to the upper end of the electrode wire  15 . The socket  12   a  of this connector  12  is connected to the measuring device or the like (not shown in the figures) via the plug  12   b  and the wire  20 . 
     A device  10  for securing a brain electrode constructed in this way is installed in the skull A of a small animal such as a mouse or a rat or the like in the manner presented below. 
     Firstly, when the tip of the guide tube  14  has been inserted, the hole a in the skull A is filled with dental cement B or the like through the cutouts  11   b  and  11   c  formed in the upper part of the casing  11 , and, as shown in FIG. 3, the guide tube and the casing  11  are secured to the skull A. When this has been done, grease or some similar lubricant is applied to the outer face of the aforementioned guide tube  14 , because it is necessary for the aforementioned guide tube  14  to be able to slide in relation to the dental cement B. 
     Next, a spanner or some similar tool is engaged to the coupling means  16   a  on the screw rods  16  and the aforementioned tool is used to rotate the screw rod  16 . The electrode holder  13  is then guided to the inner face of the casing  11  and the electrode wire  15  is lowered together with the guide tube  14  and the tip (electrode)  15   a  of the electrode wire  15  is inserted into the prescribed location inside the brain. While this is being done the conditions inside the casing  11  can be observed through the transparent casing  11 . 
     In the embodiment above, the screw rod  16  is turned using the spanner or some other tool which is coupled to its upper end but it is also possible to provide a handle in the upper end of the screw rod  16  and to turn the screw rod  16  using the aforementioned handle. It is also possible to connect a miniature motor to the upper end of the screw rod  16  and to turn the screw rod  16  by means of the aforementioned motor. 
     Furthermore, by making either the screw rod  16  or the casing  11  serve as the base line and providing a scale on the other, it is possible to check the degree of rotation of the screw rod  16  and in this way check, from outside the casing  11 , the degree of movement of the electrode holder  13 , or in other words the degree of insertion of the electrode  15   a.    
     Furthermore, in this embodiment the connector  12  is installed in the casing  11 , the aforementioned connector  12  is connected to the measuring device or the like via the wire  20 , and the aforementioned measuring device is used to measure the changes in electrical potential at the electrode  15   a  and to stimulate the nerve cells in the brain by means of a stimulator. In this case, the connector  12  or the measuring device may be optionally provided with signal transmitting and receiving means so that signals can be transmitted wirelessly between the measuring device and the connector  12 . 
     Furthermore, in the aforementioned embodiment the electrode  13  is installed so as to slide freely while abutting directly against the inside of the casing  11 , but a guide rail may be installed inside the casing  11  so that the electrode holder  13  can be guided by means of the aforementioned guide rail. 
     FIG. 4 shows another embodiment of the brain electrode securing device according to the invention. 
     This brain electrode securing device  30  is also of watertight construction and it is provided with the same main elements as the above embodiment of the brain electrode securing device  10 . The main elements have therefore been provided with the same reference symbols as for the brain electrode securing device  10  and no further explanation has been given. 
     In this brain electrode securing device  30 , at least the elements which forms the outer surface of the brain electrode securing device  30 , such as the casing  11 , the plates  18  which form the upper face of the aforementioned casing  31 , and the components of the connector  12  and the like are made from a waterproof material such as a synthetic resin or the like and are coupled to one another in watertight fashion. However, the cutouts  11   b ,  11   c  formed in the casing  11  in the embodiment shown above are not formed in the casing  31  of this brain electrode securing device  30 . 
     In this brain electrode securing device  30 , packing is interposed between the socket  12   a  of the connector  12  and the plug  12   b , and the socket  12   a  and the plug  12   b  are coupled to one another in watertight fashion. 
     Furthermore, in this brain electrode securing device  30 , an O ring (sealing element)  21  is interposed between the upper part of the screw rod  16  and the hole  18   a  in the plate  18 , and this ensures the watertight condition. 
     In addition, in this brain electrode securing device  30 , a cover  22 , which is made from a waterproof material such as a synthetic resin or the like, is arranged so as to cover the flexible baseboard  19  and the hole  11   a  which guides the aforementioned flexible baseboard  19  inside the casing  31 . In fact, if the flexible baseboard  19  leads from the connector  12  to directly inside the casing  31 , the hole  11   a  which guides the aforementioned flexible baseboard  19  inside the casing  31  becomes unnecessary and it is no longer necessary to provide the cover  22  either. 
     This casing  31  has the same main elements as the casing  11  in the embodiment above. Therefore the same symbols have been used in the figure so that no further explanation has been given. 
     Also, in this brain electrode securing device  30 , the casing  31  is secured to the skull A in the same way as in the brain electrode securing device  10  of the embodiment above. 
     However, when dental cement B is employed as the securing means the outer surface of the aforementioned dental cement B is coated with a waterproof material C. 
     This brain electrode securing device  30  according to the invention is of watertight construction so that the underwater behavior of small animals can be assessed and yet, because no special cover is required, the device is compact and the mounting operation is easy. 
     In the brain electrode securing device  40  as shown in FIGS. 5 to  7 , the casing which forms the outer surface of the device  40  is divided and is provided with a main casing part (upper part of the casing)  41  having essential elements such as an electrode holder  13 , a screw rod  16 , and a connector  12  which are the same as those arranged in the casing  11  of the device according to the embodiment above; the base (lower part of the casing)  42  which supports the main casing part  41  on the skull; coupling means  50  which connect the aforementioned base  42  and the main casing part  41 , and a cover  60  which covers the opening in the upper part of the base  42  when the device is not in use. 
     In the main casing part  41 , the horizontal section is formed into a rectangular tube shape using transparent materials in the same way as in the casing  11  of the aforementioned device  10 . This main casing part  41  has a flange  41   a  protruding outward at the lower end. In fact, this main casing part  41  has the same main elements as in the casing  11  in the embodiment above and therefore the same reference symbols have been used as in the figures and no further explanation has been given. 
     The base  42  is constructed in the form of a tube with a bottom, using a waterproof material such as a gum or synthetic resin or the like, and it has circular ribs  43  on its upper face. Grooves  44  are formed in the upper face of the circular ribs  43  and circular packing  45  is accommodated in the aforementioned grooves  44 . In addition, male screws  46  are formed in the outer circumference of the circular ribs  43 , and the guide tube insertion hole  47  is formed in the bottom wall  42   a.    
     In addition, the coupling means  50  is formed by a ring  51  having the side cross section in the shape of an L, and female screws  51   a  are formed in the internal circumferential face of the aforementioned ring  51 . This coupling means  50  engages with play in the flange  41   a  of the main casing part  41 . 
     In addition, the cover  60  is made of a waterproof material such as a gum or synthetic resin or the like and a circumferential wall which extends downward is formed on the outer surface and female screws  61   a  are formed in the internal circumferential face thereof. 
     Furthermore, in this brain electrode securing device  40 , at least the components forming the outer surface of the device  40  such as the main casing part  41 , the connector  12 , the plate  18 , the cover  22 , the base  42  and the connection means  50  are made from a waterproof material and are coupled to one another in a watertight fashion. 
     In addition, in the same way as in the device  30  according to the embodiment above, O rings (sealing element)  21  are interposed between the upper part of the screw rods  16  and the holes  18   a  in the plates  18 , and the aforementioned O rings ensures watertight condition between the screw rods  16  and the plates  18 . 
     Furthermore, a brain electrode securing device  40  constructed in this way is installed in the skull A of a small animal such as a rat or the like in the following manner. 
     Firstly, as shown in FIG. 6, the base  42  is arranged on the skull A so that the hole  47  is aligned with the hole a which has been made in the skull A, and the aforementioned base  42  is secured to the skull A using securing means such as dental cement B or the like. When dental cement B is employed as the securing means, the outer surface of the dental cement B is coated with a waterproof material C. 
     Next, when the tip of the guide tube  14  has been inserted into the hole  47  in the base  42  and into the hole a in the skull A, the flange  41   a  on the main casing part  41  is arranged over the circular ribs  43  on the base  42  and the main casing part  41  is secured to the base  42  by screwing the female screw  51   a  of the ring  51  onto the male screw  46  of the circular rib  43 . Then, the packing  45  is interposed between the flange  41   a  on the main casing part  41  and the upper face of the circular ribs  43  and this provides a watertight seal between the main casing part  41  and the base  42 . 
     When measurement is interrupted over a comparatively long period, the casing element  41  can be detached from the base  42  and, as shown in FIG. 7, the cover  60  is secured to the base  42  by screwing the female screw of the cover  60  onto the male screw of the base  42 . The cover  60  thus essentially seals off the hole a in the skull A. 
     When measurement is resumed, the cover  60  is detached from the base  42  and the aforementioned main casing part  41  is installed on the base  42  again. 
     In the casings  11 ,  31 ,  41  of the aforementioned a brain electrode securing devices  10 ,  30 ,  40  the horizontal section is in the form of a rectangular tube but, of course, the horizontal section may also be of a circular tube (cylindrical).