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Miniature manipulator with microelectrode for chronic recording of single units from freely-moving animals
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Neuroscience Research, 10 (1991) 78- 81 ':'~"1991 Elsevier Scientific Publishers Ireland, Ltd. 0168-0102/91/$0350
NEURES 00422
Technical Note
Miniature manipulator with microelectrode for chronic recording of single units from freely-moving animals Yasuhiko Tamai ~ and Hiroshi Asanuma z I Department of Physiology, VCakayama Medical College, Wakayama (Japan) and 2 The Rockefeller University, New York City (U.S.A.) (Received 27 August 1990; Revised version received 16 October 1990; Accepted 20 October 1990)
Key words: Manipulator; Microelectrode; Single units; Chronic experiment
SUMMARY We report a simple recording and stimulating system, a miniature manipulator with a microelectrode (MMM) that can be mounted on animal's skull. The system consists of a miniature manipulator and a microeleetrode which are used in one body. Several MMMs can be implanted simultaneously into the brain as the part of the manipulator is small. With this device, recording of single units from several different cortices is possible from awake and unrestricted animals.
In neurophysiological studies, many techniques have been reported for recording of single units. In general, a microelectrode is inserted into the brain by a manipulator mounted on the stereotaxic apparatus or on a chamber attached to the skull a;5. These methods are useful for experiments in which movement of the animal is restricted, but not for chronic recording of single units in unrestrained animals. One technique for chronic single unit recording is to implant a fine insulated wire into the brain 7. However, this allows the recording of only a given single unit or at best a few units selected at the time of insertion. Besides the limitation of the number of units, other problems also arise; the units may be damaged during the operation or the electrode may be displaced when the microelectrode is fixed to the skull permanently. Another approach is an application of the acute single unit recording techniques 1.2,3,6. That is, a single microelectrode is advanced by a microdrive cemented to the animal's head. By these methods large numbers of good-quality units can be collected, but the devices are not small enough and are relatively difficult to handle over a long period of time. Figure 1 schematically shows the design of the miniature manipulator with a microelectrode (MMM). A tungsten-in-glass microelectrode 8 is mounted in a small acrylic cylinder. The microelectrode (G) has a steel cap (C) which contacts with tungsten wire (H) inserted in the glass capillary (1 mm in diameter). The steel cap is in contact with a screw (A) by force produced by a spring (D). The screw is held by a nut (B) which is fixed to the Correspondence: Yasuhiko Tamai, Department of Physiology, Wakayama Medical College, 27 Kyubancho, Wakayama 640, Japan.
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A
B
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CX DE-
F
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GH
y
Fig. 1. Cross-sectional drawing of the miniature manipulator and the microelectrode. A and B = a screw and a nut; C = a steel cap glued to the glass capillary; D = spring; E = outer case of an acrylic cylinder; F = a plastic packing; G = a glass capillary electrode; H = a tungsten or platinum wire; I = a lead wire. Electric signal is led through the microelectrode, the steel cap, the screw and nut, and the lead wire. acrylic cylinder (E). The tip of the microelectrode extrudes from the acrylic cylinder through a fight plastic packing (F). The glass capillary is glued to the steel cap and the microelectrode is driven forward or backward by turning the screw. The electrode does not rotate but travels only in the vertical direction as the screw touches only the head of the steel cap. To help smooth movements of the glass capillary, the steel cap and the plastic packing were covered by silicon wax. Electric signals are led through a wire (I) soldered to the nut. The total size of the manipulator is approximately 4 mm in width and 2 0 - 2 4 mm in length (X) and the microelectrode can be moved about 4 mm along the axis. One revolution of the screw provides vertical travel of 300/Lm. The length of extrusion of the microelectrode (Y) can be selected depending on the depth of the target area in the brain. The total size of the manipulator reported here depends on the size of the parts which are selected from custom-made electric appliances. A picture of the real M M M used in our experiments is shown in Figure 2A. The M M M is implanted with a stereotaxic apparatus using a standard manipulator. The acrylic cylinder of the M M M is held with an electrode holder of the standard manipulator attached to the stereotaxic apparatus. The animal is held in the stereotaxic instrument and a small hole is opened through the skull at a desired position. Then the dura is opened and the tip of the microelectrode is inserted into the brain through the opening. After the tip of the electrode is inserted near the target, the acrylic cylinder is fixed directly to the skull by dental cement. Several MMMs can be implanted sequentially into the brain. An example of the sequential implantation of the M M M is shown schematically in Figure 2B. The frontal two MMMs (a) with short microelectrodes are implanted in the cortex close to the surface. The tips of the microelectrodes are directed towards the same region from different directions. The number of MMMs that can be implanted is limited by the space available for mounting together. An additional M M M (b) with long microelectrode is implanted in the depth of the cortex. The length of the
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A
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b
f
C
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Fig. 2. (A) A picture of the real miniature manipulator with microelectrode (MMM). (B) Schematic drawing showing an example of implanted MMMs. (C) Picture of a cat with the MMM. Four MMMs (arrows) are implanted in the brain and these are protected by an aluminium plate (b). The lead cords are submerged in dental cement and brought to the socket (a). (D) Example of spontaneous spikes recorded by the MMM at 2 weeks (upper trace) and 4 weeks (lower trace) after implantation in the ventral bank of the anterior ectosylvian sulcus.
adjusted before insertion depending on the depth of the target. Then the holes of the skull are tightly closed with dental cement after filling the space around the electrodes with sterilized saline. Figure 2C shows a cat with the M M M implanted bilaterally in the ventral bank of the anterior ectosylvian sulcus 9. Four MMMs (arrows) are embedded in the dental cement except for the top of the manipulator device which consists of the screw and nut. Each lead cord of the electrodes is submerged in the dental cement and brought to an electric socket (a). The manipulators are protected by an aluminium plate (b) which is anchored to the skull together with the electric socket. The single unit can be selected by driving the electrode forwards or backwards using the screw located at the top of the manipulator device. After finding a unit, the tip of the electrode can be left in the same position to record from the same unit for up to 4 weeks. Figure 2D shows an example of the spontaneous spikes from the ventral bank of the anterior ectosylvian suleus at 2 weeks (upper trace) and 4 weeks (lower trace) after implantation of the MMM. The electrode is
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electrode is adjusted before insertion depending on the depth of the target. Then the holes of the skull are tightly closed with dental cement after filling the space around the electrodes with sterilized saline. REFERENCES 1 Bland, B.H., Sinclair, B.R., Jorgenson, R.G. and Koen, R., A direct-drive, non-rotating version of Ranck's microdrive, Physiol. Behav., 24 (1980) 395-397. 2 Deadwyler, S., Biela, J., Rose, G., West, M. and Lynch, G., A microdrive for use with glass or metal microelectrodes in recording from freely-moving rats, EEG Clin. Neurophysiol., 47 (1979) 752-754. 3 John, E.R. and Morgades, P.P., A technique for the chronic implantation of multiple movable microelectrodes, EEG Clin. Neurophysiol., 27 (1969) 205-208. 4 Li, C.-L. and Jasper, H., Microelectrode studies of the electrical activities of the cerebral cortex in the cat, J. Physiol. (Lond.), 121 (1953) 117-140. 5 Mountcastle, V.B., Davies, P.W. and Berman, A.L., Response properties of neurons of cat's somatic sensory cortex to peripheral stimuli, J. Neurophysiol., 20 (1957) 374-407. 6 Ranck, Jr., J.B., A movable microelectrode for recording from single units in unrestricted rats. In M.I. Phillips (Ed.), Brain Unit Activity During Behavior, Charles C Thomas, Springfield, IL (1973) pp. 76-79. 7 Schmidt, E.M., Bak, M.J. and Mclntosh, J.S., Long-term chronic recording from cortical neurons, Exp. Neurol., 52 (1976) 496-506. 8 Stoney, Jr., S.D., Thompson, W.D. and Asanuma, H., Excitation of pyramidal tract cells by intracortical microstimulation: effective extent of stimulating current, J. Neurophysiol., 31 (1968) 659-669. 9 Tamai, Y., Miyashita, E. and Tsujimoto, T., Multiple cortical control in eye movements, J. Physiol. Soc. Japan, 50 (1988) 475.
Neuroscience Research, 10 (1991) 78- 81 ':'~"1991 Elsevier Scientific Publishers Ireland, Ltd. 0168-0102/91/$0350
NEURES 00422
Technical Note
Miniature manipulator with microelectrode for chronic recording of single units from freely-moving animals Yasuhiko Tamai ~ and Hiroshi Asanuma z I Department of Physiology, VCakayama Medical College, Wakayama (Japan) and 2 The Rockefeller University, New York City (U.S.A.) (Received 27 August 1990; Revised version received 16 October 1990; Accepted 20 October 1990)
Key words: Manipulator; Microelectrode; Single units; Chronic experiment
SUMMARY We report a simple recording and stimulating system, a miniature manipulator with a microelectrode (MMM) that can be mounted on animal's skull. The system consists of a miniature manipulator and a microeleetrode which are used in one body. Several MMMs can be implanted simultaneously into the brain as the part of the manipulator is small. With this device, recording of single units from several different cortices is possible from awake and unrestricted animals.
In neurophysiological studies, many techniques have been reported for recording of single units. In general, a microelectrode is inserted into the brain by a manipulator mounted on the stereotaxic apparatus or on a chamber attached to the skull a;5. These methods are useful for experiments in which movement of the animal is restricted, but not for chronic recording of single units in unrestrained animals. One technique for chronic single unit recording is to implant a fine insulated wire into the brain 7. However, this allows the recording of only a given single unit or at best a few units selected at the time of insertion. Besides the limitation of the number of units, other problems also arise; the units may be damaged during the operation or the electrode may be displaced when the microelectrode is fixed to the skull permanently. Another approach is an application of the acute single unit recording techniques 1.2,3,6. That is, a single microelectrode is advanced by a microdrive cemented to the animal's head. By these methods large numbers of good-quality units can be collected, but the devices are not small enough and are relatively difficult to handle over a long period of time. Figure 1 schematically shows the design of the miniature manipulator with a microelectrode (MMM). A tungsten-in-glass microelectrode 8 is mounted in a small acrylic cylinder. The microelectrode (G) has a steel cap (C) which contacts with tungsten wire (H) inserted in the glass capillary (1 mm in diameter). The steel cap is in contact with a screw (A) by force produced by a spring (D). The screw is held by a nut (B) which is fixed to the Correspondence: Yasuhiko Tamai, Department of Physiology, Wakayama Medical College, 27 Kyubancho, Wakayama 640, Japan.
79
A
B
-
CX DE-
F
-
GH
y
Fig. 1. Cross-sectional drawing of the miniature manipulator and the microelectrode. A and B = a screw and a nut; C = a steel cap glued to the glass capillary; D = spring; E = outer case of an acrylic cylinder; F = a plastic packing; G = a glass capillary electrode; H = a tungsten or platinum wire; I = a lead wire. Electric signal is led through the microelectrode, the steel cap, the screw and nut, and the lead wire. acrylic cylinder (E). The tip of the microelectrode extrudes from the acrylic cylinder through a fight plastic packing (F). The glass capillary is glued to the steel cap and the microelectrode is driven forward or backward by turning the screw. The electrode does not rotate but travels only in the vertical direction as the screw touches only the head of the steel cap. To help smooth movements of the glass capillary, the steel cap and the plastic packing were covered by silicon wax. Electric signals are led through a wire (I) soldered to the nut. The total size of the manipulator is approximately 4 mm in width and 2 0 - 2 4 mm in length (X) and the microelectrode can be moved about 4 mm along the axis. One revolution of the screw provides vertical travel of 300/Lm. The length of extrusion of the microelectrode (Y) can be selected depending on the depth of the target area in the brain. The total size of the manipulator reported here depends on the size of the parts which are selected from custom-made electric appliances. A picture of the real M M M used in our experiments is shown in Figure 2A. The M M M is implanted with a stereotaxic apparatus using a standard manipulator. The acrylic cylinder of the M M M is held with an electrode holder of the standard manipulator attached to the stereotaxic apparatus. The animal is held in the stereotaxic instrument and a small hole is opened through the skull at a desired position. Then the dura is opened and the tip of the microelectrode is inserted into the brain through the opening. After the tip of the electrode is inserted near the target, the acrylic cylinder is fixed directly to the skull by dental cement. Several MMMs can be implanted sequentially into the brain. An example of the sequential implantation of the M M M is shown schematically in Figure 2B. The frontal two MMMs (a) with short microelectrodes are implanted in the cortex close to the surface. The tips of the microelectrodes are directed towards the same region from different directions. The number of MMMs that can be implanted is limited by the space available for mounting together. An additional M M M (b) with long microelectrode is implanted in the depth of the cortex. The length of the
80
A
B
b
f
C
D
Fig. 2. (A) A picture of the real miniature manipulator with microelectrode (MMM). (B) Schematic drawing showing an example of implanted MMMs. (C) Picture of a cat with the MMM. Four MMMs (arrows) are implanted in the brain and these are protected by an aluminium plate (b). The lead cords are submerged in dental cement and brought to the socket (a). (D) Example of spontaneous spikes recorded by the MMM at 2 weeks (upper trace) and 4 weeks (lower trace) after implantation in the ventral bank of the anterior ectosylvian sulcus.
adjusted before insertion depending on the depth of the target. Then the holes of the skull are tightly closed with dental cement after filling the space around the electrodes with sterilized saline. Figure 2C shows a cat with the M M M implanted bilaterally in the ventral bank of the anterior ectosylvian sulcus 9. Four MMMs (arrows) are embedded in the dental cement except for the top of the manipulator device which consists of the screw and nut. Each lead cord of the electrodes is submerged in the dental cement and brought to an electric socket (a). The manipulators are protected by an aluminium plate (b) which is anchored to the skull together with the electric socket. The single unit can be selected by driving the electrode forwards or backwards using the screw located at the top of the manipulator device. After finding a unit, the tip of the electrode can be left in the same position to record from the same unit for up to 4 weeks. Figure 2D shows an example of the spontaneous spikes from the ventral bank of the anterior ectosylvian suleus at 2 weeks (upper trace) and 4 weeks (lower trace) after implantation of the MMM. The electrode is
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electrode is adjusted before insertion depending on the depth of the target. Then the holes of the skull are tightly closed with dental cement after filling the space around the electrodes with sterilized saline. REFERENCES 1 Bland, B.H., Sinclair, B.R., Jorgenson, R.G. and Koen, R., A direct-drive, non-rotating version of Ranck's microdrive, Physiol. Behav., 24 (1980) 395-397. 2 Deadwyler, S., Biela, J., Rose, G., West, M. and Lynch, G., A microdrive for use with glass or metal microelectrodes in recording from freely-moving rats, EEG Clin. Neurophysiol., 47 (1979) 752-754. 3 John, E.R. and Morgades, P.P., A technique for the chronic implantation of multiple movable microelectrodes, EEG Clin. Neurophysiol., 27 (1969) 205-208. 4 Li, C.-L. and Jasper, H., Microelectrode studies of the electrical activities of the cerebral cortex in the cat, J. Physiol. (Lond.), 121 (1953) 117-140. 5 Mountcastle, V.B., Davies, P.W. and Berman, A.L., Response properties of neurons of cat's somatic sensory cortex to peripheral stimuli, J. Neurophysiol., 20 (1957) 374-407. 6 Ranck, Jr., J.B., A movable microelectrode for recording from single units in unrestricted rats. In M.I. Phillips (Ed.), Brain Unit Activity During Behavior, Charles C Thomas, Springfield, IL (1973) pp. 76-79. 7 Schmidt, E.M., Bak, M.J. and Mclntosh, J.S., Long-term chronic recording from cortical neurons, Exp. Neurol., 52 (1976) 496-506. 8 Stoney, Jr., S.D., Thompson, W.D. and Asanuma, H., Excitation of pyramidal tract cells by intracortical microstimulation: effective extent of stimulating current, J. Neurophysiol., 31 (1968) 659-669. 9 Tamai, Y., Miyashita, E. and Tsujimoto, T., Multiple cortical control in eye movements, J. Physiol. Soc. Japan, 50 (1988) 475.