SPONTANEOUS ACTIVITY OF BETZ CELLS IN CATS WITH MIDBRAIN LESIONS

Abstract

Glass micropipettes electrodes of less than 1 u tip diameter were used to record spontaneous activity of single cells in the motor cortex of the unanesthetized cat. Observations were limited to those cells which responded antidromically to stimulation of toe pyramidal tract. When histograms are plotted of toe intervals between successive discharges, toe distribution of these intervals falls into two main categories. The corresponding patterns of activity are classified as "rhythmic discharge" and "interrupted random discharge". The rhythmic discharge is characterized by a peak in toe distribution of intervals at between 50 and 100 milliseconds with almost complete absence of intervals less than 10 msec. Interrupted random activity occurs in bursts, the distribution of intervals within the bursts being similar to the theoretical distribution for random events. This type of activity is believed to be associated with more extensive mid-brain lesions. It is suggested that the absence of short intervals during the rhythmic discharge is associated with inhibitory effects which are intermittent in preparations showing only toe interrupted random discharge pattern.