DISSOCIATED PATTERN OF ACTIVITY IN VISUAL CORTICES AND THEIR PROJECTIONS DURING HUMAN RAPID EYE-MOVEMENT SLEEP

Positron emission tomography was used to measure cerebral activity and to evaluate regional interrelationships within visual cortices and th eir projections during rapid eye movement (REM) sleep in human subject s. REM sleep was associated with selective activation of extrastriate visual cortices, particularly within the ventral processing stream, an d an unexpected attenuation of activity in the primary visual cortex; increases in regional cerebral blood flow in extrastriate areas were s ignificantly correlated with decreases in the striate cortex. Extrastr iate activity was also associated with concomitant activation of limbi c and paralimbic regions, but with a marked reduction of activity in f rontal association areas including lateral orbital and dorsolateral pr efrontal cortices. This pattern suggests a model for brain mechanisms subserving REM sleep where visual association cortices and their paral imbic projections may operate as a closed system dissociated from the regions at either end of the visual hierarchy that mediate interaction s with the external world.