Fig. 1.
Sleep-wake state neural systems. Sagittal schematic view of the rat brain depicting neurons with their chemical neurotransmitters, pathways and discharge profiles by which they influence cortical activity or behavior across the sleep/wake cycle. Waking (W) is characterized by fast (gamma, >30 Hz) activity on the cortical EEG (upper left) and high postural muscle tone on the neck EMG (lower right); slow wave sleep (SWS) by slow EEG (delta, < 4 Hz) and low tone on the EMG; and paradoxical sleep (PS) by fast EEG and atonia on the EMG. The dashed line represents the transection between the telencephalon and the rhombencephalon or brainstem following which SWS persists in the telencephalon and PS in the rhombencephalon in addition to W. Neurons that are active during W (red symbols) include cells with ascending projections toward the cortex, which stimulate fast cortical activity (filled symbols), and cells with descending projections toward the spinal cord, which stimulate motor activity with postural muscle tone typical of behavioral W (open symbols). Those with predominantly ascending projections discharge in association with fast EEG activity (gamma+) and cease firing with delta activity (delta-) to be active during both W and PS (W/PS-max active, filled red symbols). They include cholinergic (ACh), GABAergic (GABA) and glutamatergic (Glu) neurons. Those with more diffuse or descending projections discharge in association with behavioral arousal and EMG activity (EMG+) and cease firing with muscle atonia to be active during W and silent during PS (EMG+, W active, open red symbols); they include noradrenergic (NA), serotonergic (Ser), histaminergic (HA), orexinergic (Orx), glutamatergic (Glu) and some GABAergic neurons. Neurons that are active during sleep include cells with ascending projections toward the cortex, which discharge maximally with slow wave activity during SWS (gamma-, delta+, SWS-max active, blue symbols) and those with descending projections toward the hypothalamus, brainstem or spinal cord, which discharge maximally with muscle atonia during PS (EMG-, PS-max active, aqua symbols). They include MCH neurons, GABA (with some glycine, Gly) and some Glu neurons. Abbreviations: 7g, genu 7th nerve; ac, anterior commissure; ACh, acetylcholine; BF, basal forebrain; CPu, caudate putamen; Cx, cortex; DR, dorsal raphe; EEG, electroencephalogram; EMG, electromyogram; GiA, gigantocellular, alpha part RF; Gi RF, gigantocellular RF; GiV, gigantocellular, ventral part RF; Glu, glutamate; Gly, glycine; GP, globus pallidus; HA, histamine; Hi, hippocampus; ic, internal capsule; LC, locus coeruleus nucleus; LDT, laterodorsal tegmental nucleus; MCH, melanin concentrating hormone; Mes RF, mesencephalic RF; NA, noradrenaline; opt, optic tract; Orx, orexin; PH, posterior hypothalamus; PnC, pontine, caudal part RF; PnO, pontine, oral part RF; POA, preoptic area; PPT, pedunculopontine tegmental nucleus; PS, paradoxical sleep; RF, reticular formation; Rt, reticularis nucleus of the thalamus; s, solitary tract; scp, superior cerebellar peduncle; Ser, serotonin; SN, substantia nigra; Sol, solitary tract nucleus; SWS, slow wave sleep; Th, thalamus; VTA, ventral tegmental area; W, wake. Modified from [2].