Comparison of rostro-caudal brain stem influence on preoptic neurons and cortical EEG.

The changes in activity of preoptic area (POA) neurons, and cortical EEG, upon stimulation of the caudal brain stem reticular formation (CBS) and the rostral brain stem reticular formation (RBS) are compared in this study. Low frequency (LF) stimulation of the CBS (which induced EEG synchronization) and the RBS (which generally did not affect the EEG) had an excitatory influence on a majority of the affected neurons of the POA. In contrast, high frequency (HF) stimulation of the CBS (which produced EEG desynchronization in many instances) and the RBS (which induced EEG desynchronization in all instances) resulted in inhibition of a majority of the affected POA neurons. A larger number of neurons responded to HF stimulation of both brain stem regions, as compared to LF stimulation. The changes induced in the POA neurons, upon stimulation of the two brain stem reticular structures, were not dependent on simultaneous changes in the cortical EEG, except during some cases of stimulation-induced EEG desynchronization.