Theories of Sleep Sleep is an active state that is critical for our physical, mental, and emotional well-being. Sleep is also important for optimal cognitive functioning,and sleep disruption results in functional impairment. Insomnia is the most common sleep disorder in psychiatry. At any given time, 50% of adults are affected with 1 or more sleep problems such as difficulty in falling or staying asleep, in staying awake, or in adhering to a consistent sleep/wake schedule. Repair/Restoration –Sleep allows for recuperation from physical, emotional, and intellectual fatigue Survival Value –Sleep evolved to conserve energy and protect our ancestors from predators
Why Sleep? Repair and Restoration Theory –sleep enables the body and brain to repair itself after working hard all day –going without sleep causes people to be irritable, dizzy, and to have hallucinations and impaired concentration –sleep-deprived rats’ bodies work harder –BUT, how much we sleep does not depend on how much we worked that day
Evolutionary Theory - we evolved to sleep so that we would conserve energy when we were least efficient - during sleep body temperature decreases - predicts that species will sleep different amounts depending on how much they must look for food and watch for predators Why Sleep?
Circadian Rhythms: Sleep Circadian Rhythms (9.1) endogenous cycles role of the suprachiasmatic nucleus setting/resetting biological clocks Sleep (9.2) why sleep? stages of sleep Dreaming (9.3) why dream?
Suprachiasmatic Nucleus (SCN) SCN - main control center for sleep and temperature circadian rhythms
Light retinal ganglion cells send direct projections to the SCN this provides information about light to the SCN light can also alter blood-borne factors SCN is highly vascularized Melatonin secreted from the pineal gland increased levels of melatonin make you sleepy melatonin can act on receptors in the SCN to phase-advance the biological clock What Resets the Clock?
REM Sleep REM: rapid-eye movement lots of brain activity - EEG shows low voltage fast waves postural muscles are most relaxed during REM sleep loose associative thinking PGO waves - start in the pons geniculate nucleus of thalamus occipital cortex
REM Sleep neurons within the pons send inhibitory messages to the spinal cord during REM sleep this message inhibits motor neurons that project to large muscles REM sleep is still observed after damage to the pons but, no inhibition of muscle neurons…
Basal ganglia efferents to the PPN involved in the control of REM and muscular atonia. (A) Schematic model for the basal ganglia control of REM sleep B) Experimental diagram for examination of the involvement of a nigrotegmental projection in the control of REM and muscular atonia. (C) (a) Stimulation of the PPN induced REM and muscular atonia. (b) Conditioning stimulation of the lateral part of the SNr diminished the PPN-effects. (c) Conditioning stimuli applied to the mid part of the SNr did not block REM but blocked the muscular atonia (REM without atonia).
“Sometimes,a cigar is just a cigar.” - Freud, on the meaning of dreams A.K.A. Psychoanalytic theory: Dreams represent disguised symbols of repressed desires and anxieties Manifest Content: symbols used to disguise true meaning of dream Latent Content: true unconscious meaning of a dream Wish Fulfillment – Freud’s DreamTheory…
Why Dream? Activation-Synthesis Hypothesis dreams begin with episodic bursts of spontaneous activity in the Pons (PGO waves) these PGO waves partially activate certain regions of the cortex this haphazard input is combined with previous (waking) input cortex “synthesizes” a story to make sense of all the input it is receiving
The emerging concepts of sleep neurophysiology are consistent with the cholinergic-aminergic imbalance hypothesis of mood disorders>> depression is associated with an increased ratio of central cholinergic to aminergic neurotransmission. The characteristic sleep abnormalities of depression may reflect a relative predominance of cholinergic activity.
Sleep and the Immune System Sleep deprivation is correlated with a significant reduction in cellular immunity Can cause reductions in NK cells, T-cells, and monocyte function Problems tend to diminish following recovery sleep
Sleep and the Immune System Widows, whose sleep had been significantly disturbed, a decrease in the number of killer cells and a weakened immune system occurred (Stapleton, 2001) In lab rats, total sleep deprivation for four weeks can cause death by infection (Stapleton, 2001)
Sleep and the Immune System Men who received just four hours of sleep a night for four straight nights after receiving a flu shot produced half the antibodies as the control group (Weintraub, 2004)
Sleep and the Cardiovascular System Sleep deprivation increases concentrations of cytokines in the body Also increases levels of C-reactive proteins, which can cause low-grade inflammation This inflammation can damage the inner walls of the arteries, leading to possible stroke or heart disease
Blood pressure and heart rate are higher following sleep deprived nights ( Voelker, 1999 ) Men who work 60+ hours a week are twice as likely to have a heart attack as men who work 40 hours or less ( Heart Disease Weekly, 2002) Men who sleep 5 hours or less a night have twice as many heart attacks as men who sleep 8 hours or more Sleep and the Cardiovascular System
A significant link has been found between exhaustion and coronary heart disease ( Cole et. al, 1999 ) Women who have less than 5 hours of sleep have a 30% increased risk of developing coronary heart disease Sleep deprivation increases risk of heart disease in women ( Josefson, 2003 )
Sleep Deprivation and Diabetes Chronic sleep deprivation leads to insulin resistance This resistance can result in high blood glucose concentrations, leading to diabetes Men who sleep 4 hours a night for 6 straight nights lose 30% of their ability to respond to insulin --> diabetes
MS and Sleep MS causes sleep fragmentation in terms of abnormal sleep pattern Fatigue in MS could be explained also by disruption of sleep microstructure, poor subjective sleep quality and depression. There are both central and peripheral mechanisms in fatigue. The most common autonomic symptoms in MS are disorders of micturition, impotence, sudomotor and gastrointestinal disturbances, orthostatic intolerance as well as sleep disorders. The combination of fatigue and depression with sleep disorders (insomnia, restless legs syndrome) is common in MS (decreased activity of the serotoninergic and noradrenergic systems). Sleep disturbance is common in MS and is associated with treatable symptoms, including pain and nocturia. Sleep problems frequently might include initial insomnia (anxiety and pain/discomfort, in 42%), middle insomnia(nocturia,in 53% with daytime fatigue ) and terminal insomnia in 58%.