Sleep
Internal Clock
• Circadian rhythm
– Circum = about
– Dies = day
Activities that are governed by an
internal clock
•
•
•
•
Waking and sleeping
Eating and drinking
Body temperature
Secretion of hormones
Fig. 9.1
Where exactly is the biological
clock?
Suprachiasmatic Nucleus (SCN)
Figure 9.2 A sagittal view of the suprachiasmatic nucleus (SCN) and the pineal gland in the
human brain
Klein/Thorne: Biological Psychology
© 2007 by Worth Publishers
SCN
• Controls the circadian rhythm
• Location
– Hypothalamus
– Just above the optic chiasm
• Damage to the SCN
– Still sleep the same amount
– But the daily rhythm is destroyed
• Affects sleep, release of hormones
Studying the human
circadian rhythm
• Put healthy adults in a room with no
indication of time of day
– Body creates a rhythm that is about 25 hours
long
– Indicates that if not reset, biological clock is
25 hours long
– Free-running rhythm
Fig. 9.4
Studying the human
circadian rhythm
• Zeitgebers
– Reset the biological clock to 24 hours
– Position of the sun, for example
– Visual photoreceptor
– Nonvisual photoreceptor (light-dark cycle)
• Retinohypothalamic tract – passes info from
nonvisual photoreceptor to SCN
Phase-Sequence Problems
• Fig. 9.5
• Fig. 9.6
Wakefulness
• Reticular activating system (RAS)
– Hindbrain through midbrain
– Arousal of the brain, alertness
How to study sleep?
• By using something called an
electroencephalograph (EEG)
• Electro: electric signals
• Encephalo: brain
• Graph: Measure
• Attach electrodes to the scalp
Figure 9.13 EEG patterns during waking and sleeping, and a typical night’s sleep
Klein/Thorne: Biological Psychology
© 2007 by Worth Publishers
Stages of Sleep
• Caveat: there are now 3 NREM stages
(Stages 3 and 4 have been combined), but
textbook was published prior to this recent
change
Stages of Sleep
• Relaxed wakefulness
– Alpha waves
• Stage 1
– Theta waves
Stages of Sleep
• Stage 2
– Sleep spindles
– K-complexes
Stages of Sleep
• Stage 3
– Delta waves
– Transition phase into Stage 4
Stages of Sleep
• Stage 4
– Delta waves
Stages 3 and 4: slow wave sleep
Controlled by the raphé nuclei, which contains
serotonin  decreased serotonin, decreased
NREM sleep
Stages of Sleep
• Rapid Eye Movement (REM)
• EEG similar to Stages 1 and 2
REM Sleep
• Also called “paradoxical sleep”
– EEG waves similar to waking state
– Difficult to awaken person
• Loss of core muscle tone
REM Sleep
• Commonly associated with dreaming
• But, dreaming can occur during non-REM
(NREM) sleep stages (1 through 4)
• REM sleep is produced by the caudal
reticular formation
Effects of REM Sleep Deprivation
• Irritability
• Concentration difficulty
• REM rebound
Things that affect REM Sleep
• Alcohol
• Sleeping pills
• REM rebound
Dreams
Table 9.2
Klein/Thorne: Biological Psychology
© 2007 by Worth Publishers
Function of Sleep
A restorative function
•
•
•
•
Growth
Development of nervous system
Replace neurotransmitters
More active during day  need more sleep
Evolutionary Perspective
• According to this theory, how much an
animal sleeps depends on
– How much time it spends each day searching
for food
– How safe it is from predators
Evolutionary Perspective
• Cats and bats
– Eat nutritious food
– Are relatively safe
– Sleep for long periods of time
• Herbivores (plant eaters)
– Graze much of the day
– Need to look out for predators
– Sleep in short spurts
Learning and Memory
• Memory consolidation
Sleep Disorders
Sleep Disorders
• Insomnia
– Older adults, women
– Noise, discomfort
– Anxiety, depression
– Caffeine, alcohol
– Sleep apnea
Sleep Disorders
• Hypersomnia
– Sleepwalking
• Non-REM
– Night terror
• Non-REM
• Different from nightmare
– Bedwetting
• Non-REM
• Treatment: conditioning
– Narcolepsy
• REM
• Cataplexy
• Sleep paralysis