Behavioral and Neuronal Effects of EEG Synchronizing Stimuli in the Cat

Abstract

<p>Electrical stimulation of the medical thalamus (MTH) and lateral preoptic area (LPO), which produces slow, rhythmic "synchronized" waves in the cortical EEG, has been reported also to induce sleep and to inhibit neurons of the brain stem reticular formation that produce fast, irregular "desynchronized" EEG waves. The present findings confirm that MTH and LPO have significant input to brain stem neurons, but that input is not exclusively inhibitory. MTH and LPO stimuli produce discrete cycles of excitation and inhibition in reticular neurons which alternately facilitate and suppress subsequent inputs, from visual (V) and auditory (A) systems for example, which converge with MTH and LPO inputs on single reticular cells. Conversely, it was found that V and A stimuli could facilitate and suppress MTH and LPO responses. These results support the view that synchronogenic and desynchronogenic mechanisms of the cortical EEG are reciprocally organized at a subcortical level, and that the organization involves complex excitatory and inhibitory interactions. However, no convincing evidence was found to support the contention that synchronogenic stimulation of MTH or LPO induces behavioral sleep.</p>