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Psych 260Psych 260

Kim SweeneyKim Sweeney

ksweeney@cogsci.ucsd.eduksweeney@cogsci.ucsd.edu

www.cogsci.ucsd.edu/~ksweeney/psy260.htmwww.cogsci.ucsd.edu/~ksweeney/psy260.htm

Introduction to Introduction to

Physiological PsychologyPhysiological Psychology

How Much Sleep Do We Need?How Much Sleep Do We Need?

The vast amount of time spent sleeping The vast amount of time spent sleeping

suggests that sleep has a significant suggests that sleep has a significant

biological functionbiological function

��What is that function?What is that function?

��What brain mechanisms control sleep?What brain mechanisms control sleep?

�� How does sleep deprivation impact How does sleep deprivation impact

functioning?functioning?

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Why do we sleep?Why do we sleep?

�� All mammals, birds and reptiles sleep All mammals, birds and reptiles sleep ––

fish and amphibians have sleepfish and amphibians have sleep--like phaseslike phases

–– Only warmOnly warm--blooded verterbates have REMblooded verterbates have REM

–– must have an important functionmust have an important function

–– NotNot a special highera special higher--order human functionorder human function

�� Not necessarily needed in large quantitiesNot necessarily needed in large quantities

�� No clear relationship between species’ No clear relationship between species’

sleep time and activity levelsleep time and activity level

Why do we sleep?Why do we sleep?

�� Some animals sleep with one hemisphere Some animals sleep with one hemisphere

at a time!at a time!

�� Amount of sleep more predictive of Amount of sleep more predictive of

likelihood of being eaten than amount of likelihood of being eaten than amount of

physical exercise.physical exercise.

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WakefulnessWakefulness

�� During wakefulness the EEG of a normal During wakefulness the EEG of a normal

person shows two basic patterns of person shows two basic patterns of

activity:activity:

�� Alpha activity:Alpha activity:

–– regular, mediumregular, medium--frequency waves of 8frequency waves of 8––12 Hz12 Hz

–– present when a person is resting quietly, not present when a person is resting quietly, not

aroused or excited and not engaged in aroused or excited and not engaged in

demanding mental activity demanding mental activity

WakefulnessWakefulness

�� During wakefulness the EEG of a normal During wakefulness the EEG of a normal

person shows two basic patterns of person shows two basic patterns of

activity:activity:

�� Beta Activity:Beta Activity:

–– irregular, lowirregular, low--amplitude waves of 13amplitude waves of 13––30 Hz30 Hz

–– Shows Shows desynchronydesynchrony, reflecting many , reflecting many

different neural circuits engaged in active different neural circuits engaged in active

processingprocessing

–– DescynchronizationDescynchronization is indicative of a person is indicative of a person

being alert, attentive, and/or thinkingbeing alert, attentive, and/or thinking

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Three Physiological Measures of SleepThree Physiological Measures of Sleep

�� Electroencephalogram (EEG)Electroencephalogram (EEG)–– Reveals “brainwaves”Reveals “brainwaves”

�� Electrooculogram (EOG)Electrooculogram (EOG)–– Records eye movements (such as those seen Records eye movements (such as those seen during rapid eye movement (REM) sleep)during rapid eye movement (REM) sleep)

�� Electromyogram (EMG)Electromyogram (EMG)–– Detects activity (and lack thereof) in neck Detects activity (and lack thereof) in neck muscles during various sleep stagesmuscles during various sleep stages

Four Stages of Sleep EEGFour Stages of Sleep EEG

�� EEG voltage EEG voltage

increasesincreases and and

frequency frequency

decreasesdecreases as one as one

progresses from progresses from

stage 1 through 2, stage 1 through 2,

3, and 43, and 4

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Four Stages of Sleep EEGFour Stages of Sleep EEG

�� Stage 1Stage 1–– Light sleepLight sleep

–– Muscle activity slowsMuscle activity slows�� Hypnic myoclonia (myoclonic jerk)Hypnic myoclonia (myoclonic jerk)

–– EEG is similar to awake EEG, but slowerEEG is similar to awake EEG, but slower

–– LowLow--voltage, highvoltage, high--frequencyfrequency

–– Characterized by theta waves Characterized by theta waves

�� 3.5 3.5 –– 7.5 Hz waves7.5 Hz waves

�� Eyes closed, preparing to sleepEyes closed, preparing to sleep

Four Stages of Sleep EEGFour Stages of Sleep EEG

�� Stage 2Stage 2–– About 50% of our sleep is spent in stage 2About 50% of our sleep is spent in stage 2

–– Theta activity, but also…Theta activity, but also…

–– K complexes K complexes –– one large negative (upward one large negative (upward deflection) wave followed by one large positive deflection) wave followed by one large positive wavewave�� Precursor to delta activity?Precursor to delta activity?

�� Inhibitory mechanism?Inhibitory mechanism?

–– Sleep spindles Sleep spindles –– bursts of 12bursts of 12--14 Hz waves14 Hz waves

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Four Stages of Sleep EEGFour Stages of Sleep EEG

�� Stages 3 and 4 Stages 3 and 4 –––– Together known as “deep sleep” or “SWS”Together known as “deep sleep” or “SWS”

–– Stage 3 delta waves, large and slow (slower Stage 3 delta waves, large and slow (slower than 3.5 Hz), begin to appearthan 3.5 Hz), begin to appear

–– Stage 4 is almost exclusively delta wavesStage 4 is almost exclusively delta waves

SlowSlow--wave sleepwave sleep

�� Cerebral metabolic rate and blood flow Cerebral metabolic rate and blood flow

decrease (~75% of waking levels!)decrease (~75% of waking levels!)

�� Areas which show Areas which show highest highest activity during activity during

waking show waking show highest highest level of delta waves level of delta waves

during sleep, suggesting “resting brain”during sleep, suggesting “resting brain”

�� A person who is awoken during SWS is A person who is awoken during SWS is

groggy and confused, as if the brain had groggy and confused, as if the brain had

been ‘offbeen ‘off--line’ (contrast with REM). line’ (contrast with REM).

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Four Stages of Sleep EEGFour Stages of Sleep EEG

�� Progress to stage 4 sleep and then back to Progress to stage 4 sleep and then back to stages 3, 2, and REM sleepstages 3, 2, and REM sleep–– A cycle takes about 90 minutesA cycle takes about 90 minutes

�� Durations of REM periods lengthen as night Durations of REM periods lengthen as night progresses, durations of stages 3 and 4 progresses, durations of stages 3 and 4 decreasedecrease

Stages of SleepStages of Sleep

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Four Stages of Sleep EEGFour Stages of Sleep EEG

�� During REM sleep: REMs, loss of core During REM sleep: REMs, loss of core muscle tone, lowmuscle tone, low--amplitude/highamplitude/high--frequency EEG, increased cerebral and frequency EEG, increased cerebral and autonomic activity, muscles may twitchautonomic activity, muscles may twitch–– ~20% of our sleep is spent in the REM stage~20% of our sleep is spent in the REM stage

–– Each 90 minute cycle contains about 20Each 90 minute cycle contains about 20--30 30 mins of REM. mins of REM.

REM SleepREM Sleep

�� neurons within the neurons within the ponspons send send

inhibitory messages to the inhibitory messages to the

spinal cord during REM sleepspinal cord during REM sleep

�� this message inhibits motor this message inhibits motor

neurons that project to large neurons that project to large

musclesmuscles

�� REM sleep is still observed REM sleep is still observed

after damage to the after damage to the ponspons

�� but, no inhibition of muscle but, no inhibition of muscle

neurons…neurons…

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REM Sleep and DreamingREM Sleep and Dreaming

�� 80% of awakenings from REM yield reports 80% of awakenings from REM yield reports of storyof story--like dreamslike dreams

�� External stimuli may be incorporated into External stimuli may be incorporated into dreamsdreams

�� Dreams run on real timeDreams run on real time

�� Everyone dreamsEveryone dreams

�� Sleepwalking and talking are Sleepwalking and talking are lessless likely to likely to occur while dreamingoccur while dreaming

What can possibly go wrong?What can possibly go wrong?

�� InsomniaInsomnia

–– Different people require different amounts Different people require different amounts

of sleepof sleep

–– People often misjudge the amount of sleep People often misjudge the amount of sleep

they are gettingthey are getting

–– Important that the cure not be worse than Important that the cure not be worse than

the disease!the disease!

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What can possibly go wrong?What can possibly go wrong?

�� InsomniaInsomnia

–– Sleep Apnea: a cessation of breathing while Sleep Apnea: a cessation of breathing while

sleeping: causes insomnia because the body sleeping: causes insomnia because the body

panics if blood oxygen levels fall!panics if blood oxygen levels fall!

What can possibly go wrong?What can possibly go wrong?

�� NarcolepsyNarcolepsy

–– Irresistible sleep, cataplexy, sleep paralysis, Irresistible sleep, cataplexy, sleep paralysis,

hypnagogic hallucinationshypnagogic hallucinations

–– REM during waking, and often go straight to REM during waking, and often go straight to

REM (skipping SWS). REM (skipping SWS).