Neural mechanisms and architecture of sleep

This chapter explores the neural mechanisms and architectural organization of sleep, which is essential for memory consolidation, neural plasticity, metabolic homeostasis, and cognitive function. Sleep is regulated by an integrated system of homeostatic sleep pressure and circadian rhythms that is linked to distributed neural networks such as the hypothalamus, brainstem, thalamus, basal forebrain, and cerebral cortex. Control of sleep is mediated through the balance between sleep-promoting networks (e.g. ventrolateral preoptic nucleus and its GABAergic projections) and arousal-promoting (e.g. orexinergic, cholinergic, monoaminergic, and histaminergic networks). This chapter looks at sleep from the macro and micro points of view and emphasizes the distinct neurophysiological attributes and functions of NREM and REM sleep. We focus on slow-wave activity, sleep spindles, and thalamocortical oscillations as electrophysiological substrates for synaptic plasticity, memory consolidation, and large-scale network synchronization. Research in polysomnography, neuroimaging, computational neuroscience, and artificial intelligence has also shed light on the neural architecture of sleep and its role in cognition, emotional regulation, and brain health. All in all, sleep is discovered as an emergent property of integrated neural systems that has a fundamental role to play in neuropsychiatric, metabolic, and neurodegenerative disorders and further scope for translational and clinical sleep investigations.