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Permanent Implantation of Multilead Electrodes in the Brain *

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PERMANENT IMPLANTATION OF MULTILEAD ELECTRODES IN THE BRAIN* JOSE M.R. DELGADOt Anesthesia and restraint of the animal subject are the two main factors which may modify responses evoked by stimulation of the brain. However, much of the information concerning brain physiology is of necessity based upon experiments performed under one or both of these limiting circum- stances. The techniques developed thus far for the study of brain function in unanesthetized animals are described in the following paragraphs. 1. Hess,7 one of the pioneers in the field, was the first successfully to implant electrodes in the diencephalic structures of the cat. Using the sutures of the skull as reference points, a metallic frame with a super- structure is screwed to the parietal bone. This superstructure serves to support the electrodes while they are being driven into the brain. It is then removed. Remaining are the metal frame and the electrodes. Since Hess's experiments were of short duration, aseptic precautions were not taken. 2. Variations of the remote control technique have been used by Chaffee and Light,' Clark and Ward,8 Fender,' Loucks,' and Mauro.' In this method a small induction coil having terminals inside the brain is placed under the skin. Stimulation is accomplished by applying a magnetic field to the head of the animal and then inducing a current in the subcutaneous coil. The main advantage of this is that no leads pierce the skin. Some of the difficulties and limitations of the remote control techniques are: (a) the number of electrodes is limited to one or two; (b) it is impossible to record electrical activity from the brain; and (c) it is difficult to control the parameters of stimulation accurately. 3. Pachon and Delmas,'l Hunter and Jasper,' Clark and Ward,2' Hoagland,8 Lubinska and Konorski,'8 Rheinberger and Jasper,' and Gastaut' used variations of a general procedure that consisted essentially of screwing to the skull a small plastic or stainless steel base in which were inserted the

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