Activity of substantia nigra units across the sleep-waking cycle in freely moving cats

The activity of dopamine-containing substantia nigra units was recorded by means of movable 32 or 62 micrometers diameter insulated nichrome wires in freely moving cats. Nigral units displayed a slow, somewhat irregular activity during quiet waking (mean = 4.6 spikes per sec), and showed no significant change in activity during sleep. While nigral unit activity was somewhat higher during active waking, there was no relationship between unit discharge and phasic movement.