Sleep intensity is regulated by the duration of previous wakefulness, suggesting that waking results in the progressive accumulation of sleep need (Borbely and Achermann, 2000). In mammals, sleep intensity is reflected by slow-wave activity (SWA) in the nonrapid eye movement (NREM) sleep electroencephalogram, which increases in proportion to the time spent awake. However, the mechanisms respons...

Cognitive and affective processes vary over the course of the 24 h day. Time of day dependent changes in human cognition are modulated by an internal circadian timekeeping system with a near-24 h period. The human circadian timekeeping system interacts with sleep-wakefulness regulatory processes to modulate brain arousal, neurocognitive and affective function. Brain arousal is regulated by asce...

Are rapid eye movements (REMs) in sleep associated with visual-like activity, as during wakefulness? Here we examine single-unit activities (n=2,057) and intracranial electroencephalography across the human medial temporal lobe (MTL) and neocortex during sleep and wakefulness, and during visual stimulation with fixation. During sleep and wakefulness, REM onsets are associated with distinct intr...

BACKGROUND Being awake during anaesthesia is a serious complication. An anaesthetic depth monitor must discriminate in real time between wakefulness and unconsciousness. The present study created a period of wakefulness during propofol-induced hypnosis. Bispectral index (BIS), explicit and implicit memories of the awake period were investigated. METHODS Ten volunteers were studied. The calcul...

Nineteen lightly sleep-deprived healthy volunteers were examined with H2(15)O and positron emission tomography (PET). Scanning was performed during wakefulness and after the subjects had fallen asleep. Sleep stage was graded retrospectively from electroencephalogram (EEG) recordings, and scans were divided into two groups: wakefulness or synchronized sleep. Global flow was quantified, revealing...

The duration of each episode of any one electrophysiological sleep stage or any episode of intervening wakefulness was determined in three kinds of disturbed sleep, namely, in naturally impaired sleep of late middle-aged, normal people, in sleep after caffeine administration, and in sleep after hypnotic drug withdrawal. When compared with the sleep of young people, the sleep of late middle-aged...

Action of the uppermost medial internal intercostal muscles-the parasternals-during rapid eye movement (REM) is uncertain; no direct recordings exist of shortening of these muscles during sleep. Historically, motor inhibition of skeletal muscles during REM sleep is thought to cause global loss of chest wall muscle function, REM "atonia," with preservation of only diaphragm function. However, re...