Basal forebrain sleep-active neurons

The basal forebrain is an important way station in the activation of the cerebral cortex from the reticular activating system. AMPA and NMDA injections into the basal forebrain increase wakefulness and reduce sleep (Cape Jones, 2000 Manfridi et al, 1999), effects that are blocked by AMPA and NMDA receptor antagonists (Manfridi et al, 1999). The excitatory cortical projections of the basal forebrain have long been considered purely cholinergic, but many basal forebrain neurons that project to the cortex are now known to contain Glu, which may function as a co-transmitter or even as the primary excitatory neurotransmitter (Manns et al, 2001). The basal forebrain also affects vigilance via synapses to HCT cells in the lateral hypothalamus some of these synapses are glutamatergic (Henny Jones, 2006). 

I and II and also layers IV. Activity of the basal forebrain neurons is necessary for maintaining wakefulness and, functions of these and brainstem cholinergic nuclei include arousal, selective attention and REM sleep (Ch. 2). 

The rapid, low amplitude EEG activity of REM sleep, like that of waking, is sustained by cholinergic processes (Kinai Szerb, 1965 Phillis 8c Ghong, 1965), principally from neurons in the basal forebrain which project over the entire cortex (Divac, 1975 Lehmann et al., 1980 Bigl et al., 1982). Activation of the nucleus basalis of Meynert results in acetylcholine release in the cortex... 

How and why is the limbic forebrain selectively activated in REM so as to produce this kind of affective experience The how answer is that in addition to its major cholinergic innervation from the basal forebrain the limbic area receives a direct projection from the dorsolateral pontine tegmentum, where the cholinergic neurons that become selectively active in REM sleep are found in animals. PET studies can t yet tell us if this particular brain stem region is selectively activated in human REM sleep, but we hypothesize that such a homology is likely. 

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