The role of the temporal lobe amygdala in ponto-geniculo-occipital activity and sleep organization in cats.

Ponto-geniculo-occipital (PGO) spikes propagate to different structures of the limbic system, including the temporal lobe amygdala. There is direct connection between the amygdala and the pontine nuclei involved in the generation of PGO spikes. It has also been shown that both the amount and the pattern of PGO spike discharges are under the influence of several brainstem and forebrain structures. In the present work, PGO activity was analyzed in unrestrained cats submitted to low-intensity amygdaloid electrical stimulation during paradoxical sleep (PS) episodes. General sleep organization as well as number, mean duration and percentage of PS episodes, were assessed in 8-h sleep recordings during amygdaloid stimulation. Amygdaloid stimulation significantly increased PGO number, spike density and, specially, PGO burst density. No significant changes were found in PS episodes or in the slow-wave sleep. It is concluded that the amygdala plays a role in the modulation of PGO activity by means of a facilitatory influence. It is proposed that this influence is probably exerted through a positive feedback mechanism. The independence between PGO generation and PS maintenance mechanisms is emphasized.