Chapter 11 - Sleep

Question 1

What’s a biorhythm?

Answer 1

• Cyclical changes in behaviour or bodily functions.

Question 2

What are the different types of biorhythms?

Answer 2

• Circannual - yearly cycle
• Circadian - daily cycle
• Ultradian - less than a day
• Intradian - More than a day

Question 3

T/F: Circadian rhythms are less extreme in the southern and northern hemispheres.

Answer 3

• FALSE
• They’re more extreme in the two hemispheres

Question 4

T/F: Circadian rhythms are present at the cellular level.

Answer 4

• TRUE

Question 5

What type of mechanism is an biological clock?

Answer 5

• Biological clocks are produced by an endogenous mechanism that times behaviour by producing biorhythms
• Endogenous = innate to the organism

Question 6

What are free-running rhythms?

Answer 6

• Rhythms of the body’s own devising in the absence of all external cues (ex. light), so they’re driven solely by the body
• Somewhat accurate although these rhythms tend to drift in the absence of light

Question 7

What are zeitgebers?

Answer 7

• Environmental events that entrain biological rhythms
• i.e., they’re time setters
• Important because an entrained biological clock allows an animal to synchronize its daily activity across seasonal changes

Question 8

What’s the effect of light pollution on circadian rhythms?

Answer 8

• Very disruptive to circadian rhythms
• Causes behavioural consequences such as accidents daytime fatigue, altered emotions and can lead to metabolic syndromes

Question 9

What is a metabolic syndrome?

Answer 9

• Combinations of medical disorders including obesity, and insulin abnormalities that collectively increase the risk of developing cardiovascular disease and diabetes

Question 9

What’s seasonal affective disorder (SAD)?

Answer 9

• A depression disorder that occurs during winter
• 5X more common in women
• Affects up to 10% of people in the northern latitudes
• Phototherapy treatment = exposure to bright white light containing the blue frequency

Question 10

What part of the brain is mainly responsible for maintaining circadian rhythms?

Answer 10

• The suprachiasmatic nucleus (SCN) found in the hypothalamus
• If SCN is damaged, activities occur haphazardly
• SCN cells are more electrically and metabolically active in light periods
• SCN neurons maintain rhythmic activity in absence of input and output (entrainment depends on external inputs)

Question 11

What cells are responsible for transmitting light signals to the SCN?

Answer 11

• melanopsin-containing RGCs (mRGCs or ipRGCs) found on the retina
• Referred to as the retinohypothalamic tract
• mRGCs are sensitive to 460-480nm (blue light)
• These cells allow light to entrain the SCN

Question 12

Can a lesioned SCN be restored using a transplant when performed in rats?

Answer 12

• Yes, which in turn restores the circadian rhythm.

Question 13

How do we measure sleep?

Answer 13

• Use a polysomnography (PSG)
• Involves hooking up an EEG (brain), an EMG (muscles), and an EOG (eyes)

Question 14

What are the stages of waking and sleep?

Answer 14

1) Waking (W) - Includes beta rhythms
2) N1-Sleep - Feel drowsy/sleep onset starts, characterized by theta waves
3) N2-Sleep - Have now fallen asleep. Includes sleep spindles and K-complexes
4) N3-Sleep - Now in deep sleep, characterized by delta waves
5) R-Sleep - In REM sleep, characterized by beta rhythms which can include sawtooth waves

Question 15

What are the physical properties of the different sleep waves?

Answer 15

• Beta rhythms (W, R-sleep) - low amplitude, high frequency
• Theta rhythm (N1-sleep) - Slightly larger amplitude than beta, slightly lower frequency than beta.
  -Delta rhythm (N2 and N3-sleep) - High amplitude, low frequency

Question 16

T/F: PSGs only measure action potentials.

Answer 16

• FALSE
• They only measure graded potentials

Question 17

What’s the difference in dreams between N-sleep and R-sleep?

Answer 17

• N-sleep dreams cannot recall when we wake up, but for R-sleep we can (they are much more vivid and memorable)

Question 18

What’s a hypnogram?

Answer 18

• A sleep graph
• includes the cycles of N-R sleep, which occurs about 5X per night, each cycle lasts approximately 90 minutes, which comes to a total of 7.5 hours
• The cycles start N-dominant but then become R-dominant

Question 19

What are some of the major differences between N-sleep and R-sleep?

Answer 19

• N-sleep - Body temp. declines, heart rate decreases, blood flow decreases, growth level hormones increase, muscle tone is maintained, night terror can occur
• R-sleep - Very high in infancy and during growth spurts, pregnancy, and during periods of increased physical exertion, and decreases with age, mechanisms that regulate body temp. stop working, no muscle tone (atonia, so paralyzed), vivid dreaming

Question 20

What are the three contemporary explanations for why we sleep?

Answer 20

1) Sleep is a biological adaptation
2) Sleep is a restorative process
3) Sleep is for memory storage

Question 21

What’s the justification for the theory that sleep is a biological adaptation?

Answer 21

• Sleep is an energy-conserving strategy
• Predatory animals sleep more than prey animals
• Nocturnal and diurnal animals sleep when they cannot travel easily

Question 22

What’s the main hypothesis for sleep as a restorative process?

Answer 22

• Hypothesis: chemical events that provide energy to cells may be reduced during waking and are replenished during sleep
• Not a lot of evidence for this theory, as limited periods of sleep deprivation have no physiological consequences, but are associated with poorer cognitive performance

Question 23

What are some of the effects of R-sleep deprivation?

Answer 23

• Increased tendency to enter R-sleep in subsequent sleep sessions
• R-sleep rebound - More than usual amount of R-sleep in subsequent sleep sessions
• May weaken the immune system as well

Question 24

What are the two general memory categories?

Answer 24

1) Explicit - consciously recalled. Can be episodic (autobiographical) or semantic (knowledge) 2) Implicit - Unconsciously recalled

Question 25

What are place cells?

Answer 25

- Found in the hippocampus and fire preferentially when animal enters a specific location in its environment - These similar patterns of activity are replayed in their N-sleep which helps consolidate memories - Similar to building a cognitive map - Ties together N-sleep and explicit memories

Question 26

What did Maquet and colleagues (2000) discover regarding the importance of R-sleep in implicit memory?

Answer 26

- They used PET imaging to record brain activity while human subjects learned a serial reaction time task - Results - similar patterns of neocortical activation during task learning and R-sleep. Demonstrated how memories can be stored elsewhere other than the hippocampus during REM

Question 27

What role does the reticular activating system play in sleep and waking?

Answer 27

- Important for inducing waking EEG and behaviour - If damaged, RAS produces a slow-wave EEG and can result in a coma

Question 28

What two general pathways originate from the RAS?

Answer 28

- Ventral: RAS > hypothalamus > cortex - Dorsal: RAS > thalamus > cortex

Question 29

What happens if either the ventral or dorsal pathways of the RAS are damaged?

Answer 29

- Ventral damaged - lose awareness (vegetative state) - Dorsal damaged - lose arousal (coma)

Question 30

What two major brainstem systems project via the ventral pathway that contributes to awareness?

Answer 30

1) Basal forebrain - contains large cholinergic cells that secrete ACh into neocortical neurons to stimulate a waking EEG 2) Median Raphe Nucleus (midbrain) - contains serotonergic neurons that project to the neocortex; also stimulates waking EEG

Question 31

When are ACh and 5-HT projections activated?

Answer 31

- ACh projections - activated EEG pattern when the rat is alert but immobile - 5-HT projections - activated EEG pattern when the rat moves

Question 32

What's the peribrachial area?

Answer 32

- A group of ACh neurons which are part of the RAS and contribute to R-sleep - Lesioned - reduces R-sleep - Stimulated - induces R-sleep

Question 33

What other neural activity occurs once the peribrachial area initiates R-sleep?

Answer 33

- Sends signals to the medial pontine reticular formation, which sends signals to the motor neurons of the spinal cord - Also sends signals to the beta forebrain nuclei, which induces beta activity for R-sleep

Question 34

What's insomnia?

Answer 34

- The inability to fall asleep, stay asleep, or experience satisfactory sleep - Comorbid with anxiety and depression - Highest risk is for women over 60 - Can be treated with sedative-hypnotic drugs (sedation - low dose; hypnosis - high dose)

Question 35

What are the consequences of sleeping-pill-induced insomnia?

Answer 35

- Promotes N-sleep, but deprive user of R-sleep - Tolerances can also develop, which can lead to a drug dependence insomnia

Question 36

What's fatal familial insomnia?

Answer 36

- Almost complete inability to sleep - Genetic, caused by a mutation of PrP gene on chromosome 20 (very rare)

Question 37

What's hypersomnia?

Answer 37

- Disorder of falling asleep at inappropriate times, or having difficulty staying awake - Includes narcolepsy

Question 38

What are some of the symptoms of narcolepsy?

Answer 38

- A rare condition - Can include sleep paralysis, cataplexy, hypnagogic hallucinations, excessive daytime sleepiness, mental cloudiness, memory problems, depressed mood - Immediately go into R-sleep

Question 39

What's cataplexy?

Answer 39

- State of atonia occurring while a person is awake and active; linked to strong emotional stimulation - While in atonic condition, person may experience hypnagogic hallucinations

Question 40

What's the role of the hypothalamus in narcolepsy?

Answer 40

- The hypothalamus contains orexin-producing cells that send projections to many different brain regions and are involved in maintaining wakefulness/suppressing R-sleep - Research has shown that around 90% of these orexin-producing neurons are lost in humans with narcolepsy with cataplexy