Neural activity in the brain is altered across the sleep-wake cycle, allowing periods of rest alternating with activity. Yet, some neurons decrease their discharge during sleep, whereas others increase their discharge during sleep, relative to waking. Such different cell populations within the brainstem, hypothalamus and basal forebrain generate the different states of wakefulness, slow wave sleep (SWS) and paradoxical sleep (PS, or rapid eye movement sleep, REMS). As revealed by juxtacellular recording and labeling of neurons in the basal forebrain (BF), sets or pairs of excitatory (glutamatergic or cholinergic) and inhibitory (GABAergic) cells function either in parallel, to promote by their discharge cortical activation or behavioral arousal (together with postural muscle tonus), or in opposition, to effect cortical de-activation or behavioral quiescence (together with postural muscle atonia). The activity of each neuron is likely regulated in a homeostatic manner, such that prolonged activity results in changes in its receptors
Barbara JONES, Dpt of Neurology and Neurosurgery, McGill University, Montreal Neurological Institute, Montreal, Quebec, Canada