A new multielectrode for chronic recording of intracortical field potentials in cats

The analysis of intracortical field potentials in freely moving animals may help to reveal the origin of evoked potential components displaying characteristic changes in behavioral experiments. The authors describe a chronically implantable multielectrode made of 7 teflon insulated platinum wires of 75 microns diameter. The novelty of this multielectrode is that the wires are not glued together but penetrate into the cortex independently. In the final position the cut ends serving as recording surfaces are situated in the cortical tissue below each other at equal distances of 300-400 microns. This arrangement made possible the artifact free recording of the evoked field potentials from the different depths of the auditory cortex for months. Phase reversal, known from the classical studies, could be observed only in the first surface positive component, while the late waves appeared homogeneously throughout the whole depth of the cortex.