ABSTRACT
Hyperarousal has been heavily implicated in sufferers of insomnia, and functional neuroimaging has shown increased cerebral glucose metabolism during both wake and sleep in insomniacs. The activation of extrastriate and limbic structures, combined with a deactivation of primary visual and prefrontal cortices, appears to indicate the existence of a closed processing loop during rapid eye movement (REM) sleep. Slow waves are prominent characteristics of the later stages of nonrapid eye movement sleep and consist of highamplitude delta waves at 1–4 Hz and a slower oscillatory rhythm of less than 1 Hz. Rapid eye movements are some of the most prominent hallmarks of REM sleep and are believed to be related to the ponto-geniculo-occipital waves identified through cellular recordings in animals. Sleep disturbances are a common facet of depression and include problems in sleep continuity, reductions of slow-wave sleep, decreased REM latency, and increased REM density.
