State-related discharge of neurons in the brainstem of freely moving box turtles, Terrapene carolina major.

We have performed the first study of neuronal activity in freely-moving reptiles. 23 brainstem units were recorded from areas throughout the reticular formation, during wakefulness and quiescence in the box turtle. These units responded to various sensory stimuli and increased firing rates in relation to motor activity during wakefulness. All but one unit showed significant decreases in discharge during quiescence. Group I cells (32%) fired mostly during active movements and exhibited silent periods of 5 min or longer during quiescence while group II cells (68%) maintained slow tonic activity in quiescence. Polygraphic data showed no consistent, cyclically occurring phasic events during quiescence.