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Chapter 3

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Department
Psychology
Course
Psychology 2011A/B
Professor
Imants Baruss
Semester
Spring

Description
Alter States of Consciousness: SLEEP Sleep physiology and behaviour The Nervous System • Nerve Cells – associated with the processing of information • Spinal Cord – made up of nerve cells inside the backbone, widens upwards to become the brainstem • Thalamus – top of the brainstem, located center of the head • Cerebral cortex – multiply folded, wraps around lower part of the brain • Neuron – nerve cell; cell body had branching projections called dendrites (the receiving end of the neuron) and the axon (the transmitting end) - Messages along neurons care actually changes in the electrical potentials across the cells’ walls created through electrochemical processes - Neurotransmitters – chemicals released into the intercellular fluid for communication between nerve cells - Receptor sites – where chemicals attach along the dendrite or cell body of a subsequent cell • Pacemakers – groups of nerve cells in various parts of the brain that synchronize the electrochemical activity of other groups of nerve cells • The brain is NOT dormant during sleep - Lilly tested this by climbing into an isolation tank  Found out that removal of almost all sensory stimulation did not cause sleep Polysomnography • If the electrochemical activity of groups of cells can become synchronized, is it possible to measure any resultant collective voltage changes? - YES, some voltage changes can be measured, measured by electrodes on various parts of the scalp which detect changes in electrical potential across the dendritic membranes • Electroencephalograph (EEG) – observes electrical potential over time - Primary instrument that has been used for defining the physiological changes associated with sleep - Types of frequency bans recorded by EEG  Beta waves – 13+ cycles per second (cps)  Alpha waves – 8 to 13 cps  Theta waves – 4 to 7 cps  Delta waves – less than 4cps - Shorter more rapid waves tend to be of lesser amplitude whereas longer waves of lower frequency tend to be of greater amplitude • Electrooculography (EOG) – used for detecting eye movements through electrodes taped close to the eyes • Electromyography (EMG) – measures muscle tension through electrodes places beneath the chin • Polysomnography – recordings of various physiological measures during sleep • Computerized polysomnography – computer records, scores, and summarizes sleeping events (alternative to technicians inspecting paper recordings) Sleep Stages • In waking state, EEG reveals BETA activity with SOME mixed ALPHA activity and OCCASIONAL theta. - EOG shows rapid eye movements and eye blinks, and the EMG indicates high levels of muscle activity - For 85% to 90% of people, relaxing and closing eyes results in the occurrence of alpha rhythm - Some people experience alpha-delta sleep, consist of large amplitude alpha rhythms that are 1 to 2cps slower than waking alpha occurring through sages 1 to 4 • Stage 1 - 1 to 7 minutes - K complexes – a waveform lasting 0.5 seconds that consist of a sharp negative components immediately followed by a positive slow wave of smaller amplitude and - sleep spindles – a brain wave of about 12-14cps in frequency, lasting 0.5 to 1.5 seconds - EMG is generally at a low amplitude relative to wakefulness - Eye movement is infrequent and brief after appearance of k complexes and spindles • Stage 2 - 10 to 25 minutes - Sleep deepens, high amplitude delta waves more frequent - About one to three K complexes per minute would occur during stage 2 in young adults - About three to eight spindles per minute would occur during stage 2 in normal adults • Stage 3 and 4 - Slow-wave sleep - Stage 3 lasts few minutes - Stage 4 lasts 20 to 40minutes - When Delta waves slower than 2cps occupy 20% of the sleep record sleeper is in stage 3 - When Delta waves slower than 2cps occupy 50% of the sleep record sleeper in in stage 4 - No eye movements and low muscle tension • 80 minutes from sleep onset there is a change in the polysomnograph indicating a transition to yet another sleep stage • Sawtooth waves of 2cps to 6cps • Changes in EEG, EOG and EMG occur together • REM sleep - Rapid eye movement, in burst or singly - Few minutes to 15 minutes - Often accompanies by sawtooth waves and brief facial muscle activity - Phasic REM sleep – muscle twitching with burst of eye movements - Tonic REM sleep – few to no eye movements or muscle activity - Penile erections in men and changes in erectile tissue in women within first few minutes of REM sleep - Highly activated brain in a paralyzed body - Paradoxical sleep • NREM sleep - Non-rapid eye movement - Stages 1 to 4 - Relatively inactive yet actively regulating brain in a movable body Patterns of Sleep Stages • NREM and REM sleep is repeated in cycles - First cycle approx. 70 to 100 minutes - Second and later cycle approx. 90 to 120 minutes - Total of 4 to 6 NREM-REM sleep cycles a night • Amount of time spent in a slow-wave sleep decreases in the second cycle and may disappear fully in later cycles, while REM sleep periods tends to increase each cycle • Average REM sleep cycle is 22 minutes • EEG patterns of NREM sleep emerge over the first 2 to 6 months of life • Sleep latency – time that it takes to fall asleep • Sleep efficiency – the ration of actual time spent asleep to time spent in bed • Sleep continuity – overall balance of sleep and wakefulness during a night of sleep • Wakefulness within sleep accounts for 5% of the night • Stage 1 sleep constitutes 2% to 5% • Stage 2 sleep constitutes 45% to 55% • Stage 3 sleep constitutes 3% to 8% • Stage 4 sleep constitutes 10% to 15% • REM sleep constitutes 20% to 25% • Percentages differ according to age • Infants enter REM sleep 50% of their sleep period Sleep Mentation Arousal • It is easiest to awaken someone from stage 1 and hardest from stage 4 • Waking someone from REM varies in difficulty • Nearly impossible to awaken a child in first cycle slow wave • It is easier to awaken someone with stimuli that is significant to the sleeper (e.g. infants cry to sleeping mother) - Meaningful stimuli more likely to evoke K complexes than meaningless • Point: we monitor at least some sensory stimuli while we sleep and wake up if they are too intense or significant to us • Coma – an altered state of consciousness in which awareness of self and environment is lost and there is no meaningful response to external stimuli or inner needs - Associated with decreased cerebral metabolic activity and inability to arouse someone through the use of stimulation - Persistent vegetative state – physiological functions are preserved • Sleep is natural, transient, periods and reversible • Akinetic mutism – during wakefulness, those with this condition maintain an alert appearance but they do not exhibit signs of awareness or cognition Dreaming • Eugene Aserinsky’s – when participants were awake from REM sleep, 20 of 27 times they reported detailed dreams usually involving visual imagery vs. participants awakened from NREM sleep, only 2 of 23 reported such dreams and 2 others having reported the feeling of having dreamed. • Nightcap – portable computerized sleep monitoring system - Participants randomly awakened and to report dreams - Those waken during REM had longer reports (average 148 words) • Two arguments to dreams being occasionally present during NREM sleep 1. Some of the NREM reports of our subjects were practically indistinguishable from typical REM dreams 2. Even when they could not recall a dream on awakening from slow wave sleep, participants would frequently make comments about having dreamt but is now gone. • Investigators suggest cortical activity is sufficient enough for dream production during sleep, however, depending on the amount of mental activity, the level of cortical activation may differ. Such that, during slow wave sleep, memory resources are at a low level of cortical activation, while during REM sleep cortical activity in memory resources is high The Purpose of Sleep Sleep Need • The most obvious cons of total sleep deprivation is sleepiness - Decrease in cognitive performance (motivation only lasts 48 to 64hrs) - Longer periods of sleep loss have greater impacts on task performance (speed more affected than accuracy) - Mood strongly affected by cognitive ability which is strongly affected by motor activity - Hallucinations commonly reported after 48hrs of sleep deprivation, become more intense as sleep loss progresses • Long terms effect of sleep loss can lead to death (rats died after 11 to 22 days without sleep) • The tendency to enter REM sleep increases when REM sleep is deprived • REM sleep rebound is found during undisturbed recovery sleep, with increased amount of REM sleep for three recovery nights, thus there seems to be a need for sleep • Biological rhythms – plays a role in the length and timing of sleep - Circadian rhythms – 24hrs cycles generated by an internal circadian pacemaker system  Increases the tendency for sleep
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