Abstract

Why?

How?

Summary and Conclusions

References

Discussion
Board

The basal forebrain serves as the ventral, extra-thalamic relay to the cerebral cortex from the brainstem reticular activating system. Receiving input from multiple neurotransmitter specific afferents from the brainstem, the large relay neurons project in a widespread, though topographically organized manner upon all regions of the cortex. A significant proportion of these cells contain and release acetylcholine, which has the capacity to depolarize and drive into tonic discharge the cortical neurons, and thus to stimulate the change in EEG pattern from high voltage slow waves, typical of slow wave sleep (SWS), to low voltage fast waves, typical of cortical activation during waking and paradoxical sleep (PS). Cholinergic neurons are in turn depolarized by glutamate, noradrenaline, histamine and neurotensin, neurotransmitters contained in their afferents from the brainstem and posterior hypothalamus. Microinjections of these substances into the basal forebrain, elicit high frequency gamma EEG activity and waking or PS, whereas other substances which arrest the discharge of cholinergic cells attenuate high frequency gamma EEG activity. In addition to cholinergic neurons, other large neurons also project to the cerebral cortex including GABAergic neurons and neurons as yet unidentified as to their neurotransmitter. Electrophysiological studies have indicated that cholinergic and non-cholinergic neurons have different intrinsic properties and discharge profiles, such that they could influence cortical activity in different yet potentially correlated ways to pace rhythmic slow and fast activity. Accordingly, the basal forebrain relay would modulate cortical activity across the sleep-waking cycle by stimulating cortical activation and also by pacing and thereby coordinating cortical activity across distributed cortical regions, such as to provide for globally integrated activity during cortical arousal.

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Presentation Number SAjones0891
Keywords: activating system, sleep-wake state, cholinergic, GABAergic, EEG