Cognitive neuroscience of sleep

Abstract

Mechanism is at the heart of understanding, and this chapter addresses underlying brain mechanisms and pathways of cognition and the impact of sleep on these processes, especially those serving learning and memory. This chapter reviews the current understanding of the relationship between sleep/waking states and cognition from the perspective afforded by basic neurophysiological investigations. The extensive overlap between sleep mechanisms and the neurophysiology of learning and memory processes provide a foundation for theories of a functional link between the sleep and learning systems. Each of the sleep states, with its attendant alterations in neurophysiology, is associated with facilitation of important functional learning and memory processes. For rapid eye movement (REM) sleep, salient features such as PGO waves, theta synchrony, increased acetylcholine, reduced levels of monoamines and, within the neuron, increased transcription of plasticity-related genes, cumulatively allow for freely occurring bidirectional plasticity (long-term potentiation (LTP) and its reversal, depotentiation). Thus, REM sleep provides a novel neural environment in which the synaptic remodeling essential to learning and cognition can occur, at least within the hippocampal complex. During nonREM sleep Stage 2 spindles, the cessation and subsequent strong bursting of noradrenergic cells and coincident reactivation of hippocampal and cortical targets would also increase synaptic plasticity, allowing targeted bidirectional plasticity in the neocortex as well. In delta nonREM sleep, orderly neuronal reactivation events in phase with slow wave delta activity, together with high protein synthesis levels, would facilitate the events that convert early LTP to long lasting LTP. Conversely, delta sleep does not activate immediate early genes associated with de novo LTP. This nonREM sleep-unique genetic environment combined with low acetylcholine levels may serve to reduce the strength of cortical circuits that activate in the ~50% of delta-coincident reactivation events that do not appear in their waking firing sequence. The chapter reviews the results of manipulation studies, typically total sleep or REM sleep deprivation, that serve to underscore the functional significance of the phenomenological associations. Finally, the implications of sleep neurophysiology for learning and memory will be considered from a larger perspective in which the association of specific sleep states with both potentiation or depotentiation is integrated into mechanistic models of cognition.

Sleep apnoea and the brain: a complex relationship

“…It has been argued that cognitive improvements in treated OSA patients may reflect increased stability of brain activity during sleep, allowing for a crucial synaptic repair/maintenance to occur and counteracting toxic effects of arousal and hypoxic effects of OSA 50,55 . This argument is concordant with findings showing that the neurochemical and gene environments of sleep and sleep activity patterns present crucial window periods during which the brain can restore cellular homeostasis, increase signal to noise ratio, and reinforce neuronal circuitry for subsequent cognitive processing demands 18,56,57 . oxidative stress and misfolding of cellular proteins 57,58 .…”

“…given that each of the sleep stages with its attendant alterations in neurophysiology is associated with facilitation of important functional learning and memory processes 18 . In OSA patients, the proportion of stage N2 nREM sleep has been shown to increase, while proportions of stages N1, N3 and REM sleep decrease 44 .…”

“…Moreover, its role in seizure aggravation in epilepsy, several neuropsychiatric disorders and stroke has also been argued 2 . The progressive changes in sleep quality and structure, along with changes in the cerebral blood flow, neurovascular and neurotransmitter changes, the cellular redox status and neural regulation in OSA patients may constitute a contributing factor to cognitive decline, also seen with healthy aging, but present to a much greater extent in neurodegenerative diseases 1,[16][17][18][19] .…”

Different Simultaneous Sleep States in the Hippocampus and Neocortex

“…For instance, the finding that theta and spindle power is especially strong during REM/ TR may have functional relevance as both states and frequencies are important to memory consolidation. 54 It would be worthwhile for future studies to explore the possibility of a functional role for this asynchrony in memory consolidation.…”

Sleep and Heat Related Changes in the Cognitive Performance of Underground Miners: A Possible Health and Safety Concern

“…Sleep deprivation leads to dysfunction measurable on a number of dimensions ranging from cellular responses [67,68] to societal outcomes [69]. Anywhere on that continuum of sleep deprivation induced changes are issues that pertain to the thesis proposed here: miners who do not acquire adequate sleep are more likely to develop physical and cognitive deficits that could lead to workplace accidents.…”