Single-unit activity in cat's isolated midbrain.

The midbrain was isolated by two brainstem transections, pretrigeminal and premesencephalic. In the isolated midbrain, particularly within the reticular formation, EEG activity was greatly depressed. On the other hand, single-unit spike activity remained at a high level. The spatial density of active reticular units and the rate of their spontaneous activity were at least not smaller than those in the midbrain of the cat with only a pretrigeminal transection. Thus the flat EEG record is not necessarily a sign of the absence of neural activity.