Sleep

1
Sleep
2
Three Minute Review - Motivation

• MOTIVATION
• Pleasure centre
• similar effects in humans rats
• rats go to extremes to stimulate pleasure centre
• dopamine appears to be critical neurotransmitter
• EMOTION
• Why do we have emotions?
• Communication, decision-making, attention
  memory, interpersonal relations
• Two dimensions
• emotion x arousal
• Arousal
• sympathetic vs. parasympathetic nervous system
• Yerkes-Dodson law
• subjects perform best at moderate levels of
  arousal
• optimal level of arousal depends on difficulty of
  task

3

• Theories of Emotion
• Common Sense
• bear ? fear ? heart races
• James-Lange
• bear ? heart races ? fear
• facial feedback theory
• Cannon-Bard
• bear ? heart races fear
• Schachters Attribution Theory
• emotion is a combination of bodily sensations and
  cognitive appraisal of situation
• bear ? heart races realize dangerous situation
  ? fear
• misattribution of emotion
• Brain Areas Involved in Emotion
• amygdala

4
Question of the Day

• Patients with spinal cord damage do not feel as
  many effects of sympathetic nervous system
  activation as normal subjects. These patients
  also report feeling less intense emotions than
  normal subjects. In fact, the degree of
  emotional loss is greater the higher up in the
  spinal cord the damage occurred. Which of the
  following theories of emotion best explains this
  result?
• Common Sense theory
• Cannon-Bard theory
• James-Lange theory
• Facial Attribution theory
• Misattribution of Emotions theory

5
Biological Rhythms

• Circannual rhythms
• 1 year
• e.g., migration, hibernation
• Infradian rhythms
• gt1 day, lt 1 year
• e.g., menstruation
• Circadian rhythms
• 1 day
• circ about dia day (about a day)
• e.g., sleep, temperature
• Ultradian rhythms
• lt 1 day
• e.g., heartbeat, respiration

6
Circadian Rhythms

• daylight cues bodily changes temperature and
  sleep

7
Video

• (Brain, Disk 1, 13, Sleep Circadian Rhythms,
  start at 220, ends at 603, 343 total)
• How did Michel Siffre study the circadian rhythm
  for 7 months in 1972? What cues to time were
  available to him? How did his body know what
  time it was?
• How long is the natural circadian rhythm for the
  majority of adults?

8
Desynchronized Cycles
9
Jet Lag

• flying westbound
• time is earlier there so you have to stay up
  later
• flying eastbound
• time is later there so you have to go to bed
  earlier
• most people find this much harder
• baseball teams that fly east win fewer games than
  those that fly west (37 vs. 44)

arrive London UK 800 a.m. (300 a.m. in
Ontario) Do you nap right away (then your
schedule is way off) or stay up all day till its
local bedtime?
leave London Ontario 900 p.m. (200 a.m. in the
UK)
arrive London Ontario 200 p.m. (700 p.m. in the
UK) Just try to stay up a few extra hours and
youll be fine
leave London UK 100 p.m. (800 a.m. in Ontario)
10
Other Sleep Disruptions

• Switch to daylight savings time
• lose an hour of sleep in April ? 7 more traffic
  accidents
• Blue mondays
• Shift work
• more accidents happen after employees have
  undergone shift changes
• accidents due to human error are most likely to
  happen in the middle of the night (Three Mile
  Island, 1979 Chernobyl, 1986 Exxon Valdez,
  1989) or with sleep-deprived employees or
  decision makers (Space Shuttle Challenger, 1986).

11
How does the body know what time it is?

• aside from the primary visual pathway (retina ?
  thalamus ? occipital lobe), other pathways from
  the retina go to other areas
• suprachiasmatic nucleus (SCN) in the hypothalamus
• SCN ? pineal gland

12
Pineal Gland

• Rene Descartes thought it was the seat of the
  soul
• Really, its just an endocrine (hormone) gland
• secretes melatonin at night (with little secreted
  during the day)

• melatonin taken 1-2 hours before bed may help
  induce sleep
• some people use it to treat jet lag

13
Do you really need sleep?

• Peter Tripp, 1959
• Radio DJ who participated in a Wake-a-thon
• sleep deprived for 200 hours (8 days)
• took a lot of amphetamines to keep awake
• hallucinations, paranoia, psychosis friends said
  he was never quite the same afterward
• was it the speed or the sleep deprivation?
• Randy Gardner, 1963
• science fair project
• broke record for continuous wakefulness 264
  hours (11 days)
• used no drugs, not even caffeine
• supervised by William Dement, sleep researcher
• managed remarkably well
• some hallucinations, irritability, slurred
  speech, confusion, paranoia
• slept 15 hours after waking marathon ended

14
Sleep Deprivation

• become really tired, esp. 200 - 600 a.m.
• can cause lapses in attention and memory
• microsleeps
• fall asleep for a few seconds or a minute
• eyelids droop and you become less responsive to
  stimuli
• people are often unaware that they blanked out
• can be fatal when driving
• driving tired can be worse than driving drunk
• after being awake 18 hours, your performance is
  comparable to a blood alcohol level of 0.05 ( 3
  drinks in one hour for a 150 lb male)

15
How can we measure sleep?

• Electroencephalogram (EEG)
• measures voltage difference between any two
  points on the scalp (usually with many pairs of
  electrodes compared)
• different states ? different waveforms

16
What do the waves mean?

• specific wave forms are reliably associated with
  specific states
• each electrode sums the output of many, many
  neurons
• Analogy like holding a microphone over a
  football stadium and trying to figure out what
  the group sounds are telling you

17
What do the waves mean?

• When each neuron is doing its own thing, the
  pattern looks like irregular high frequency noise
  
• When the neurons are doing things in synchrony,
  the pattern looks like regular low frequency noise

18
Sleep Waves

• different waves characterize different stages
• awake, REM sleep
• irregular high frequency waves indicate
  unsynchronized activity
• middle stages
• weird blips like spindles and K-complexes
• deep sleep
• low frequency waves (e.g., delta waves in Stage
  4) indicate synchronized activity

19
Rapid Eye Movement (REM) Sleep

• eyes move rapidly under closed eyelids
• when awoken from REM sleep, subjects are most
  likely to report that they were dreaming (though
  in non-REM sleep, subjects may report sleep
  thoughts (Ever had a Tetris dream?)
• lose muscle tone ? paralyzed (but can move
  during non-REM sleep, tossing and turning)

20
Progression through the stages

• Things to note
• progress from Stage 1 to 4 then back up and into
  REM
• first REM period after 90 minutes (if not
  sleep-deprived) and every 90 minutes thereafter
• spend more time in deep stages in early evening,
  more time in light stages towards morning
• REM periods typically get longer as evening
  progresses

21
Why do we sleep?

• Isnt sleep just a waste of time? Why bother?
• No one knows for sure, but there are some
  interesting ideas floating around
• Restoration Theory
• Your body needs to rest and recover
• runners sleep more after a marathon
• regular exercise can help sleep
• Preservation Theory
• why risk being killed if you can only get food in
  the day?

22
(No Transcript)
23
The rest of the time they were better off
sleeping in a protected shelter hidden away from
predators.
24
Is there a blood chemical that accumulates while
were awake?
Some Siamese twins who share a common blood
supply show independent sleep cycles.
Eng and Chang Bunker 1811-1874
Fully Awake
Right Hem Asleep
Left Hem Asleep
Dolphins show independent sleep/wake cycles in
the two hemispheres
25
Brain Structures Involved in Sleep

• Reticular Activating System (RAS)
• stimulation ? awakelike EEG waves
• damage ? coma, sleeplike EEG waves
• Pons (bridge)
• damage to pons can reduce or abolish REM sleep
• has connections to other brain areas to activate
  cortex, start eye movements and block movements
  during REM

26
What do dreams mean? Two Theories

• 1) The Interpretation of Dreams (1900)
• dreams are a meaningful output of the
  subconscious mind
• manifest content the dream as the dreamer
  remembers it
• latent content what the dream symbolizes that is
  disguised to protect the dreamer

Sigmund Freud
27
What do dreams mean? Two Theories

• 2) Activation Synthesis Hypothesis
• neural stimulation from the pons activates other
  brain areas that are involved in waking
  consciousness
• the sleeping mind tries to make sense of random
  neural firing by weaving a story
• during REM, frontal lobes are deactivated (dreams
  lack logical planning and thinking) and limbic
  system is activated (dreams often have emotional
  content, esp. negative emotions)
• dreams are side effects of random neural activity

J. Allan Hobson (contemporary sleep expert)
28
Infants dream a lot!

• perhaps this indicates that dreaming is crucial
  for developing brain pathways?

29
Dreaming May Help You Remember

• REM sleep may help you consolidate memories
  (i.e., encode them from short term to long term
  memory)
• Sleep helps you learn (Karni et al., 1994)
• trained subjects on a hard visual task
• subjects with normal nights sleep performed well
  the next day
• subjects who had been awoken during non-REM
  periods performed well the next day
• subjects who had been awoken during REM sleep
  performed poorly the next day
• Even naps may help (Mednick et al., 2002)
• trained subjects on a hard visual task for a long
  time
• as training wore on, subjects who did not nap got
  worse
• subjects who took a nap maintained good
  performance
• a 1-hour nap was better than a 30-minute nap