Comparison of Multiple-unit and Electroencephalogram Activity recorded from the same Brain Sites during Behavioural Conditioning

Abstract

IN an attempt to find a more sensitive measure of brain activity than that yielded by EEG recordings, and sample more extensively than is possible with single unit, micro-electrode recordings, we have examined multiple-unit activity recorded and integrated from various brain sites in cats during behavioural conditioning procedures. Multiple-unit recordings of central activity have been made in acute^1,2 and in chronic³ preparations, but this technique has not been used in learning experiments⁴. In the work reported here, multiple-unit discharge was picked up by chronically implanted stainless steel insectpin electrodes, amplified, and recorded on one beam of a Tektronix 502 oscilloscope. This unit activity was concurrently integrated and the output of the integration circuit recorded on the second beam of the oscilloscope. Simultaneously with these recordings, EEG activity was picked up through the same electrode and written out on a Grass model IIIG EEG machine. In this communication a comparison will be made between the multiple-unit and EEG activity recorded from the same brain sites during the acquisition and extinction of a conditioned hindleg flexion response.