The amygdala: a critical modulator of sensory influence on sleep.

The influence of external stimuli and the memories of both unpleasant and pleasant conditions clearly can have a considerable impact on the quality of sleep. The amygdala, a structure that plays an important role in coding the emotional significance of stimuli and is heavily interconnected with brainstem nuclei known to be involved in sleep control, has received little attention from sleep researchers. We report on a series of studies, focusing on its central nucleus (Ace). Presence of serotonin (5-HT) in Ace caused a rapid change of state when injected in rapid- eye-movement sleep (REM) compared with non-REM (NREM) injections. A 5-HT antagonist released ponto-geniculo-occipital waves (PGO) into NREM. Stimuli conditioned by pairing with aversive stimuli in a fear-conditioning paradigm significantly increased sound-elicited PGO and reduced REM. Copyright 2000 S. Karger AG, Basel