Visualization of sleep influences on cerebellar and brainstem cardiac and respiratory control mechanisms

Cerebellar and vestibular structures exert substantial influences on breath ing and cardiovascular activity, particularly under conditions of extreme c hallenges. Influences from these structures, as well as from the ventral me dullary surface, are greatly modified during sleep states. Vestibular lesio ns abolish the pronounced phasic autonomic variation found in the rapid eye movement steep state, and spontaneous ventral medullary surface activity, as assessed by optical procedures, is greatly diminished in that state. Neu ral responses from the ventral medullary surface to hypotensive challenges are enhanced and appear "undampened" during the rapid eye movement sleep st ate. Functional magnetic resonance imaging reveals activation to blood pres sure challenges in widespread brain areas of humans, and especially in cere bellar sites, such as the fastigial nucleus. A subset of victims of sudden infant death syndrome, a sleep-related disorder, appear to succumb from car diovascular failure of a shock-like nature, and often show neurotransmitter receptor deficiencies in the ventral medullary surface, caudal midline rap he hypotensive regions, and the inferior olive, a major afferent relay to t he cerebellum. Afferent and efferent vestibular/cerebellar structures, or s ites within the cerebellum may mediate failure mechanisms in sudden infant death syndrome and a number of other sleep-disordered breathing and cardiov ascular syndromes. (C) 2000 Elsevier Science Inc.