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A method for implanting removable electrodes in chronic preparations
A METHOD
FOR IMPLANTING REMOVABLE ELECTRODES IN CHRONIC PREPARATIONS 1
J. SUTIN, P H . D . ,
L. S. VAN ORDEN, M . D . 2 AND B. TREMBLY, M . D . e
Department o f ,4natono,, Yale University School o f Medicine, New Ha yen ( U.S.A. ) (Received for publication: September 27, 1960) An adaptation of a small, commercially available coaxial connector 3 has proven to be a satisfactory and convenient system for chronic implantation of electrodes into the brain. This apparatus permits the depth of electrode penetration to be changed, and allows removal and replacement of the electrode when polarization occurs. It consists of a receptacle which penetrates the skull and a mating cap to which is attached a bipolar concentric electrode. The electrode fits snugly through the receptacle and may be withdrawn and replaced several times without excessive damage to the brain. The silver plated receptacle is 10 mm in length and threaded on both ends (Fig. 2A). The lower end is readily turned into a burr hole made with a ~40 drill (Fig. IB). Removal of the center conductor leaves a lumen lined with a teflon sleeve which will admit an insulated 25 or 26 gauge bipolar concentric electrode. It may be enlarged to accept larger stainless steel tubing for the injections of
crystalline drug according to the method described by MacLean (1957). The electrode consists of a length of teflon insulated 26 gauge stainless steel tubing which is cemented to the cap so as to pass through the lumen of tile receptacle and secured by screwing the cap onto the receptacle. The threaded portion of the cap turns independently of the electrode so that the latter does not twist inside the brain. Lead-off wires are soldered to the electrode center wire and to the barrel, which is insulated from the cap. These components are illustrated in Fig. 2. The receptacle is implanted into the skull under stereotaxic guidance and aseptic conditions. The ~40 drill passes through a length of steel tubing (Fig. 1A) attached to the stereotaxic instrument. A ,~4-48 tap (Fig. IC)may be used to start the threads in the bone. The receptacle is attached to the same tubular holder by means of an adaptor (Fig. IE) so that it may be threaded into the burr hole without altering the vertical alignment. 'The receptacle is cemented to the skull with acrylic resin i and a cap fitted with a stylet (Fig. 3) is attached to retain patency of the lumen until an electrode is placed into it. Experience with more than 100 implantations indicates that there is minimal cortical reaction beneath the implanted receptacle, which does not pierce the dura. When the animal is to be used for experimental observation, the cap with
Fig. 1 Apparatus for implanting miniature receptacles: A Tubular aligning guide mounted on carrier of stereotaxic instrument. B. Drill. C. Tap. D. Adaptor for mounting tap in alignment guide. E. Adaptor for mounting receptacle in alignment guide. F. Wrench. fashioned from aluminum channelling for affixing cap to receptacle.
i ! i f ( ! ! ; ,'~ 5i
t Aided by a grant from the Dysautonomia Association, Inc. USPHS Post Doctoral Fellow Ultramicrominiature receptacle # 61-01 with ~62~31 mating cap. Manufactured by Microdot Inc. 220 Pasadena Avenue, So. Pasadena, California. 462
Fig. 2 A. Microdot receptacle. B. Mating cap. C. Bipolar concentric electrode cemented to cap. D. Same as C but with a lead soldered to the cap for a ground or EEG recording. 4 Simplex, Dental Filling Ltd., London, England.
463
CHRONIC IMPLANTED ELECTRODES
Fig. 3 Receptacles in place in skull showing cap with stylet. Acrylic resin has not yet been applied. TABLE I Distance in m m from the surface of the skull to the Horsley-Clark zero plane (CAT)
Lateral Horsle),-Clark Levels (ram) I 4 8 10
Anterior Horsley-Clark LeJ,els (mm) 0
2
22.9 23.0 22.2 22.5 21.1 21.2 . . .
4 23.0 22.4 21.3 .
6 23.0
22.2 21.l .
stylet is removed, the dura punctured with a sterile sharp needle, and an electrode of desired length is inserted into the receptacle. Electrode length may be determined by inspection of Table I which indicates the distance from surface of the skull to the Horsley-Clark zero plane. The microdot receptacle is usually threaded 2.5 3 m m into the skull leaving a 4 m m distance from the base of the attached cap to the skull-surface. Thus, the length of the electrode required to reach any given depth is determined by adding 4 m m to the value calculated from the table. The lead-off wires from the electrode are attached to the input cable of the recording apparatus by means of a Winchester miniature plug attached to the animal's harness. The receptacle itself may be used as an indifferent or EEG electrode by means of an additional wire soldered directly to the cap. Histologic study of the electrode tracts indicates that up to three insertions through the same
8 22.8 22.2 20.9
10
11
12
13
14
15
16
17
22.5 22.0 20.7 19.5
22.4 21.8 20.4 19.3
22.0 21.6 20.1 19.0
21.9 21.7 20.3 --
21.8 21.4 20.1
21.5 21.1 20.0 18.5
21.4 20.9 19.5 -
20.9 20.8 19.6 18.4
receptacle do not produce unusually great damage to the brain. This system of electrode implantation has a number of advantages: the components are commercially available, require a simple apparatus for stereotaxic implantation, and permit multiple electrode insertions into the same tract. If there is to be a long interval between observations, this system is particularly useful in obviating the c o m m o n ly observed changes in electrode impedence due to polarization during the first several weeks following implantation. This method has been used successfully in the cat and, with minor changes, in the rat and rabbit as well. REFERENCE MACLEAN, P. D. Chemical and electrical stimulation of hippncampus in unrestrained animals. A. M. A. Arch. Neurol. Psychiat., 1957, 78 : 113-127.
Re]erenee: SUTIN,J., VAN ORDEN,L. S. and TREMBLY,B. A method for implanting removable electrodes in chronic preparations. Electroenceph. din. Neurophysiol., 1961, 13: 462-463.
FOR IMPLANTING REMOVABLE ELECTRODES IN CHRONIC PREPARATIONS 1
J. SUTIN, P H . D . ,
L. S. VAN ORDEN, M . D . 2 AND B. TREMBLY, M . D . e
Department o f ,4natono,, Yale University School o f Medicine, New Ha yen ( U.S.A. ) (Received for publication: September 27, 1960) An adaptation of a small, commercially available coaxial connector 3 has proven to be a satisfactory and convenient system for chronic implantation of electrodes into the brain. This apparatus permits the depth of electrode penetration to be changed, and allows removal and replacement of the electrode when polarization occurs. It consists of a receptacle which penetrates the skull and a mating cap to which is attached a bipolar concentric electrode. The electrode fits snugly through the receptacle and may be withdrawn and replaced several times without excessive damage to the brain. The silver plated receptacle is 10 mm in length and threaded on both ends (Fig. 2A). The lower end is readily turned into a burr hole made with a ~40 drill (Fig. IB). Removal of the center conductor leaves a lumen lined with a teflon sleeve which will admit an insulated 25 or 26 gauge bipolar concentric electrode. It may be enlarged to accept larger stainless steel tubing for the injections of
crystalline drug according to the method described by MacLean (1957). The electrode consists of a length of teflon insulated 26 gauge stainless steel tubing which is cemented to the cap so as to pass through the lumen of tile receptacle and secured by screwing the cap onto the receptacle. The threaded portion of the cap turns independently of the electrode so that the latter does not twist inside the brain. Lead-off wires are soldered to the electrode center wire and to the barrel, which is insulated from the cap. These components are illustrated in Fig. 2. The receptacle is implanted into the skull under stereotaxic guidance and aseptic conditions. The ~40 drill passes through a length of steel tubing (Fig. 1A) attached to the stereotaxic instrument. A ,~4-48 tap (Fig. IC)may be used to start the threads in the bone. The receptacle is attached to the same tubular holder by means of an adaptor (Fig. IE) so that it may be threaded into the burr hole without altering the vertical alignment. 'The receptacle is cemented to the skull with acrylic resin i and a cap fitted with a stylet (Fig. 3) is attached to retain patency of the lumen until an electrode is placed into it. Experience with more than 100 implantations indicates that there is minimal cortical reaction beneath the implanted receptacle, which does not pierce the dura. When the animal is to be used for experimental observation, the cap with
Fig. 1 Apparatus for implanting miniature receptacles: A Tubular aligning guide mounted on carrier of stereotaxic instrument. B. Drill. C. Tap. D. Adaptor for mounting tap in alignment guide. E. Adaptor for mounting receptacle in alignment guide. F. Wrench. fashioned from aluminum channelling for affixing cap to receptacle.
i ! i f ( ! ! ; ,'~ 5i
t Aided by a grant from the Dysautonomia Association, Inc. USPHS Post Doctoral Fellow Ultramicrominiature receptacle # 61-01 with ~62~31 mating cap. Manufactured by Microdot Inc. 220 Pasadena Avenue, So. Pasadena, California. 462
Fig. 2 A. Microdot receptacle. B. Mating cap. C. Bipolar concentric electrode cemented to cap. D. Same as C but with a lead soldered to the cap for a ground or EEG recording. 4 Simplex, Dental Filling Ltd., London, England.
463
CHRONIC IMPLANTED ELECTRODES
Fig. 3 Receptacles in place in skull showing cap with stylet. Acrylic resin has not yet been applied. TABLE I Distance in m m from the surface of the skull to the Horsley-Clark zero plane (CAT)
Lateral Horsle),-Clark Levels (ram) I 4 8 10
Anterior Horsley-Clark LeJ,els (mm) 0
2
22.9 23.0 22.2 22.5 21.1 21.2 . . .
4 23.0 22.4 21.3 .
6 23.0
22.2 21.l .
stylet is removed, the dura punctured with a sterile sharp needle, and an electrode of desired length is inserted into the receptacle. Electrode length may be determined by inspection of Table I which indicates the distance from surface of the skull to the Horsley-Clark zero plane. The microdot receptacle is usually threaded 2.5 3 m m into the skull leaving a 4 m m distance from the base of the attached cap to the skull-surface. Thus, the length of the electrode required to reach any given depth is determined by adding 4 m m to the value calculated from the table. The lead-off wires from the electrode are attached to the input cable of the recording apparatus by means of a Winchester miniature plug attached to the animal's harness. The receptacle itself may be used as an indifferent or EEG electrode by means of an additional wire soldered directly to the cap. Histologic study of the electrode tracts indicates that up to three insertions through the same
8 22.8 22.2 20.9
10
11
12
13
14
15
16
17
22.5 22.0 20.7 19.5
22.4 21.8 20.4 19.3
22.0 21.6 20.1 19.0
21.9 21.7 20.3 --
21.8 21.4 20.1
21.5 21.1 20.0 18.5
21.4 20.9 19.5 -
20.9 20.8 19.6 18.4
receptacle do not produce unusually great damage to the brain. This system of electrode implantation has a number of advantages: the components are commercially available, require a simple apparatus for stereotaxic implantation, and permit multiple electrode insertions into the same tract. If there is to be a long interval between observations, this system is particularly useful in obviating the c o m m o n ly observed changes in electrode impedence due to polarization during the first several weeks following implantation. This method has been used successfully in the cat and, with minor changes, in the rat and rabbit as well. REFERENCE MACLEAN, P. D. Chemical and electrical stimulation of hippncampus in unrestrained animals. A. M. A. Arch. Neurol. Psychiat., 1957, 78 : 113-127.
Re]erenee: SUTIN,J., VAN ORDEN,L. S. and TREMBLY,B. A method for implanting removable electrodes in chronic preparations. Electroenceph. din. Neurophysiol., 1961, 13: 462-463.