A method for rapid implantation of multielectrode systems.

The implantation of several chronic electrodes at the same time was needed for the studies in which both evoked slow potential and multiple unit neural activity of different brain sites were recorded during classical conditioning in freely moving cats. The recording electrodes were made of 25-75 microns insulated stainless steel or nichrome wires which were inserted into a thin hypodermic needle of a fixed, calibrated length. The fast implantation system described here is based on the use of a stereotaxic frame as a stand for a drill and as a support for an electrode holder with which the electrodes were implanted through precision holes drilled directly according to the coordinates of the brain atlas. The connecting pins of each electrode were inserted to a connector during implantation. The described implantation system allows short distances (0.5 mm) between electrode shafts and free determination of the depth of each electrode. Because fixing of an individual electrode with dental cement to the skull is not needed during the initial phase and the precalibrated electrodes need no adjustments during implantation, considerable time savings can be achieved.