A FUNCTIONAL-ROLE FOR REM-SLEEP IN BRAIN MATURATION

The biological function of REM sleep is defined in terms of the functi ons of neural processes that selectively operate during the REM sleep state. The high amounts of REM sleep expressed by the young during a p eriod of central nervous system plasticity suggest that one function o f REM sleep is in development. The phenomenon of activity-dependent de velopment has been clearly shown to be one mechanism by which early se nsory experience can affect the course of neural development. Activity -dependent development may be a ubiquitous process in brain maturation by which activity in one brain region can influence the developmental course of other regions. We hypothesize an ontogenetic function of RE M sleep; namely, the widespread control of neuronal activity exerted b y specific REM sleep processes help to direct brain maturation through activity-dependent developmental mechanisms. Preliminary tests of the hypothesis have been conducted in the developing feline visual system , which has long been known to incorporate information derived from vi sual experience in establishing neuronal connectivity. We find that su ppression of REM sleep processes by an instrumental REM deprivation pr ocedure results in a significant enhancement of the effects of altered visual experience by monocular occlusion. Bilateral brainstem lesions that selectively block the occurrence of ponto-geniculo-occipital (PG O) waves are sufficient to produce similar results. These data indicat e that the propagation of phasic influences during REM sleep interacts with other processes subserving neural development. This source of in fluence appears not to derive from the environment but rather stems fr om an intrinsic source of genetic origin. Examination of the neural ac tivity associated with PGO waves in the lateral geniculate nucleus rev eals a distribution of facilitatory influence markedly different from that induced by visual experience. We conclude that REM sleep directs the course of brain maturation in early life through the control of ne ural activity.