Lecture 11 - Feb 15.pdf

When we are awake, our EEG shows two basic patterns: - Alpha activity consists of regular, medium frequency waves PSYC211 Lecture 11 - Feb. 15 (8-12 Hz). Electrophysiological Measurement of Sleep: - • Beta activity is generally associated wave forms that are • Electrodes are attached to the subjects’ scalp to record electrical activity of the brain. The amplifier records an irregular at an amplitude of 13-30 Hz. Beta activity is desynchronous; it’s a reflection of different • neural circuits actively processing information at the same time.le activity recorded as an electromyogram (EMG) • Electrodes placed around the eyes monitor eye movements recorded as an electrooculogram (EOG) BraBrain Activity When We’re Awake and At Rest: Stage 2 of Sleep Stage 2 of Sleep • When we are awake, our EEG shows two basic patterns: • Alpha activity consists of regular, medium frequency waves (8-12 Hz) When we are awake, our EEG shows two basic patterns: After abo•tBeta activity Stage 1 of Sleepociated wave forms that are irregular at an amplitude of 13-30 Hz. Beta activity is - Alpha activity consists of regular, medium frequency wavesixture ofuits actively processing information at the same time Stage 1 of Sleep: -8-1Sleep spindles are short bursts of waves (12-14 Hz) which occur - Beta activity is generally associated wave forms that are which occur irregular at an amplitude of 13-30 Hz.g sleep stages 1-4. - Older people show more K complexes. K complexes are sudden, Beta activity is desynchronous; it’s a reflection of different neural circuits actively processing information at the same time. •cWhen we get drowsy, we show theta activity (3.5-7.5 Hz). This is the transition between wakefulness and sleep troccur spontaneously at approximately 1 per minute and can be Stage 2 of Sleep: When triggered by unexpected noise.ctivity (3.5-7.5 Hz). This is the transition between wakefulness and sleep. • After about 10 minutes, the EEG becomes irregular with mixture of theta activity, sleep spindles and K complexes After a•oSleep spindles are short bursts of waves (12-14 Hz) which occur between 2-5 times a minute during sleep stages 1-4 theta activity, slStage 1 of Sleep K complexes. • Older pStages 3 and 4 of Sleepexes. K complexes are sudden, sharp waveforms. They are found during stage 2 only. They occur spontaneously at approximately 1 per minute and can be triggered by unexpected noise Stage 3 and 4 of Sleep:es 3 and 4 of Sleepwaves (12-14 Hz) which occur between 2-5 times a minute during sleep stages 1-4. - Older people show more K complexes. K complexes are sudden, sharp waveforms. They are found during stage 2 only. They occur spontaneously at approximately 1 per minute and can be triggered by unexpected noise. 2 When we get drowsy, we showtheta activity (3.5-7.5 Hz). This is the transition between wakefulness and sleep.high-amplitude delta waves (less that 3.5 Hz). They occur more frequently in stage 4.ta waves (less than 3.5 Hz). They occur more frequently in stage 4 StaNeocortical neurons oscillate during slow wave activityaves (less that 3.5 Hz). They occur more frequently in stage 4. Neocortical neurons osNeocortical neurons wave activity oscillate during slow Stages 3 and 4 of Sleep wave activity REM Sleep: REM Sleep Finally, about 90 minutes after the beginning of sleep, we enter REM sleep characterized by Rapid Eye Movements • Finally, about 90 minutes after the beginning of sleep, we enter REMeta and beta activity • The EMG becomes silent (no muscle tone). In fact, apart from occasional twitching, muscles are totally inactive during REM sleep characterised by Rapid Eye Movements. sleep Sleep Patterns: The acStages 1-4 are referred to as non-REM sleepnkled with theta and beta activity. • Stages 3-4 are referred to as slow-wave sleep because of slow, high amplitude delta waves • At stage 4, you’re usually in deep sleep. Can’t be awakened by noise. Cerebral blood flow and oxygen consumption The EMG becomes silent (no muscle tone). Infact, apart from occasional twitching, muscles are totally inactive during REM sleep. • During REM you don’t react to noise but you can be aroused by meaningful stimuli Dreaming occurs during REM sleep. Cerebral blood flow and oxygen consumption increase. In REM sleep, muscles are • inactive 90-Minute Sleep State: • Sleep alternates between REM and non-REM patterns of sleep • Each sleep cycle is about 90 minutes long (20-30 minutes of REM sleep) Mental Activity During Sleep: • People who report their dreams are ‘conscious’ during sleep • There is high cerebral blood flow to the visual association cortex which may account for the visual hallucinations that occur during dreams • There is low blood flow to the primary visual cortex (because the retina is not receiving any light) and the prefrontal cortex (which makes dreams temporally disorganized) Comparative Analysis of Sleep: !  Stag•s In bottle nosed dolphins, the two hemispheres sleep independently so they remain behaviorally alert • When lions have gorged themselves on a kill, they may sleep continuously for three days! !  Functions of Slow-Wave Sleep (I):ow-wave sleep because of slow, high ampl•tuEffects of sleep deprivation: human studies • Lack of sleep affects cognitive abilities rather than physical abilities !  At stage • yYou never regain lost sleep after sleep deprivationoise. Cerebral blood flow and oxygen consumption decrease. • Presence of delta activity and low levels of physiological activity (i.e. Low cerebral metabolic rate and cerebral blood flow) during slow-wave sleep indicates that the brain is resting !  During RE• yThe brain must restore the effects of oxidative stress Functions of Slow-Wave Sleep (II): • Effects of sleep deprivation: animal studies !  Dreaming occA yoked-control procedure is when both animals receive the same amount of treatment at the ‘same’ time • consumpti•n Both rats received equal amounts of exercise but only one animal was sleep deprived (the experimental rat) • A compute recorded EEG of both rats. If 90-minute sleep state EEG of ‘experimental rat’ indicated that it was falling asleep, the motor was activated forcing both animals to exercise • Experimental rat reduced its total sleep by 87%. The yoked rat reduced its total sleep by 31% Functions of REM Sleep: Highest proportion of REM sleep is seen during • the active phases of development: approximately 70% of a newborn infants sleep 4 is REM sleep. In adulthood, only 15% of sleep is dedicated to REM sleep Consolidates memories of events of previous • !  Sleep altern