The influence exerted by Nembutal on reactivity of the superior colliculus neurons

Effects of a Nembutal upon responses of the superior colliculus neurons were analyzed in pretrigeminal cats. Most cells were studied during the spindly barbiturate pattern in the EEG. In this condition collicular neurons lose their spontaneous activity, become sluggish in their reactivity to stimuli moving at high velocity, and less sensitive to direction of movement. After a further increase in the anesthesia down to the isoelectric EEG pattern the responses of neurons were gradually depressed and finally neurons became non-driveable by visual stimulation. A possible mechanism responsible for the reduction of the cells excitability is discussed.