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Year 3 - Biological > Biological Psychology of Sleep and Dreaming > Flashcards

Biological Psychology of Sleep and Dreaming Flashcards

1
Q

Circadian Rhythms

A
  • Most organisms cycle between periods of alertness and inactivity that follows an approximately 24hr cycle
  • Patterns of alterness and inactivity are not driven directly by light, but by evolutionary niche adaptations
    • Diurnal Rhythm
    • Nocturnal Rhythm
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2
Q

Diurnal Rhythm

A
  • Active mostly during the day
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3
Q

Nocturnal Rhythm

A
  • Active during dark periods
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4
Q

Definition of sleep (Siegel, 2008)

A
  1. Rapidly reversible state of immobility and greatly reduced sensory responsiveness
    • When people are asleep they are less responsive to stimuli in their environment
  2. Sleep is homeostatically regulated (lost sleep - sleep rebound)
    • Likely to sleep more the next day to make up from the loss of sleep
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5
Q

Bullfrogs and sleep

A
  • Show circadian patterns of activity and inactivity
  • More reactive to external stimulation during inactive period
    • Suggesting they don’t sit with the defintion of Siegel, (2008)
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6
Q

Sleep studied in the lab

A
  • Key problems:
    • Psychology studies of sleep are difficult because the participant is not responsive while they sleep
    • People normally sleep in the comfort of their own homes—sleeping is a very private activity
  • Solution: Take a range of physiological measures using a range of sensors and have people sleep in a sleep lab
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7
Q

Methods of measuring sleep in the lab

A
  • Electroencephalography (EEG)
  • Electromyography (EMG)
  • Electrooculography (EOG)
    *
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8
Q

Electroencephalography (EEG)

A
  • Measures ekectrical activity on the scap arising from the synchronous activity of large populations of (mainly cortical - neurons in the cerebral cortex) neurons
  • Commonly defined by frequency (Hz), Amplitude (V)
  • Often in EEG, some transformation is conducted on the data afterwards to separate this complex signal into multiple different bands of activity that contribute to forming the complex signal
  • Activity that is very slow, activity that repeats 4 times per second is defined as delta band
  • Other bands include theta, alpha, beta and gamma
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9
Q

Activation of cells

A
  • Cells in their post-synaptic phase show a polarization where half of the cell body is positively charged and the other hald is negatively charged
  • This forms the electrical diploe which can be detetced on the surface of the head (curved shape)
  • Neurons that exists in the cerebral cortex - structure where they are arranged in parallel formation and contrast in a lot of subcortical areas, neurons look a bit more more erratic, meaning that they can sum together to create larger electrical currents that are measured on the scalp
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10
Q
A
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11
Q

Electromyography (EMG)

A
  • Measures electrical acitivty cayse by muscle contractions
  • Assess chnages in muscle activity as a proxy for tension and relaxation during sleep
    • Signal increases when muscle is used
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12
Q
  • Electrooculography (EOG)
A
  • Measures eye electrical acitivity associated with eye movements (e.g., blinks, lateral eye movements - left to right, vertical -up and down)
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13
Q

Stages of sleep

A
  • Alert wakefulness
  • Stage 1
  • Stage 2
  • Stage 3
  • Stage 4
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14
Q

Wakefulness

A
  • Beta Activity (16-31 Hz)
    • Rapid, low voltage, irregular oscillations
    • Recorded aboce most brain locations
  • Alpha Activity (8-15 Hz)
    • Higher voltage and lower frequency than beta
    • Observed primarily over posterior regions
    • Modulated by eye-closing
    • Relaxed and resting brain state
  • Wake EEG often oscillates between alpha and beta activity, while neither activity is observed much during sleep
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15
Q

Stages 1 & 2

A
  • 40-50% of total sleep
  • Stage 1
    • Lowering of EEG frequency
    • Lowered heart rate and reduction of muscle tension
  • Stage 2
    • Similar to stage 1 with some additional features
    • Sleep spindles (periodic 12-14 Hz bursts)
    • K-complexes
  • If awakened during initial stages 1-2 people will often deny that they are sleeping
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16
Q

Stages 3 & 4

A
  • 15-20% of total sleep
  • Slow wave sleep
    • Dominated by delta activity. EEG waveforms are slow and high amplitude
    • Deepest form of sleep with lowest ability to generate arousal
    • Reduced heartrate and respiration
    • Muscle relaxation, but movement still occurs
    • Increased parasympathetic nervous system activity (i.e., rest and digest)
17
Q

REM Sleep

A
  • Rapid Eye Movement (REM)
  • 20-25% of total sleep
  • Characteristics of REM sleep
    • Low amplitude, high frequency EEG activity (like wakefulness)
    • Associated with fast rapid eye movements (Electrooculography)
    • Loss of tone (i.e., relaxation) of core muscles
  • Other correlates of REM sleep
    • Brain activity (blood flow, neural firing) increases to waking levels.
    • Increased variability in heart rate, blood pressure, breath rate
    • Twitching of muscles at the extremities
    • Penile erection in males, pelvic thrusting and uterine contractions in females
18
Q

REM and Dreaming - Early Studies

A
  • Early evidence supported REM sleep to dreaming
    • 80% of awakenings from REM sleep accompanied by dream re-call
    • Only 7% of non-REM sleep associated with dreams recall
    • Non-REM sleep associated with more general feelings (e.g., falling)
19
Q

REM = Dreams: Counterevidence

A
  • Many people often recall no dreams after sleeping but have normal REM sleep cycles
  • It could be that REM sleep is necessary, but not sufficient for dreams
  • Taking anti-depressants greatly reduces or abolishes REM sleep but do not report reduced rates of dreaming
  • REM and Dreaming depended on different brain areas
    • REM sleep is generated largely in the pontine brainstem
    • Lesions to this brain area typically abolish REM sleep
    • Lesions to pontine brain steam do not abolish dreaming
    • Loss of dreaming and preserved REM sleep is observed with lesions to PTJ and VM frontal lobes
20
Q

Theories of Sleep

A
  • Recuperation Theory
  • Adaptation Theory
21
Q

Recuperation Theory

A
  • Being awake depletes energy resources in some way, and sleeps helps us to return to normal baseline levels (i.e., sleep maintains homeostasis).
  • Explains why lack of sleep is often recovered after sleep deprivation
  • Slow-wave sleep in particular activates the bodies “rest-and-digest” systems (reduced heart rate, respiration, increased digestion).
  • Similar to set-point theory of hunger!
22
Q

Adaptation Theory

A
  • Evolutionary theory
  • Sleep is associated with reduced metabolic costs than being awake (sleep conserves energy)
  • Sleep can help to enforce evolutionary niche (nocturnal or diurnal?)
  • Human example: Human’s are not well adapted to life in the dark
  • No set-point in adaptation theories
    • We are motivated to sleep, but we don’t need it to survive (EXTREME VIEW)
    • Sleep schedules should be modifiable – we don’t need x amount of sleep given wakefulness
23
Q

Animal Studies of Extreme Sleep Deprivation

A
  • Carousel Apparatus: Used to deprive rats of sleep over long time periods
  • When EEG signals sleep, platform rotates and knocks animal into water
  • Yoked control: Rat subjected to same rotations as experimental, but not tied to this rat’s sleep
  • Result: Experimental rat dies after about 12 days
  • Stress confound
    • Post-mortems reveal swollen adrenal glands, gastric ulcers, and internal bleeding.
    • The rats died from stress, not lack of sleep
    • It is very difficult to do sleep studies in animals for these reasons
24
Q

The effects of sleep deprivation

A
  • Logic: We can learn about the function of sleep by assessing the effects of sleep deprivation in humans
  • Confounding Factors
    • Stress
      • We often lose sleep because of some other stressor
      • Problems at work
      • Relationship breakdown
      • Illness
      • Personal finances
  • Ill-health attributed to sleeping may often be caused by the co-occurring stress
25
Q

Sleep deprivation studies in humans

A
  • Experimental studies: Participants are prevented from sleeping—ranges from reduced sleep schedules to total sleep deprivation.
  • Next day assessment of sleepiness, mood, cognitive function, performance, physiology, and so forth.
  • Reliable effects of sleep deprivation:
    • 1) Increased self-reported sleepiness (people feel drowsy and desire sleep)
    • 2) Increased Negative affect/ bad mood
  • These findings are consistent with the idea that sleep has a replenishing effect between days
26
Q

Sleep Deprivation and Decision Making - Iowa Task

A
  • Iowa Gambling task: A test of risky decision making
  • Frontal lobe damage and IGT
    • Frontal brain damage—particularly in ventromedial prefrontal cortex—is often associated with the more persistent selection of “bad decks”
    • Patients with vmPFC damage often show increased anger and frustration, and less empathy and compassion
    • Sleep deprivation, it has been suggested, leads to reduced activity in vmPFC
27
Q

Sleep Deprivation and Decision Making - Killgore et al., 2006

A
  • Killgore et al., 2006. Does sleep deprivation have a negative impact on decision making in the Iowa Gambling Task (IGT)?
  • Study 48 participants who performed IGT at baseline and then again after experimenters kept them awake for 49 hours

Found:

  • Baseline participants starts of making relatively poor decisions (award driven) but over time once they get to the end of the study they are starting to make more advantageous decisions - so they are making better choices
  • When they are sleep deprived - start off doing relatively poorly as you would expect and they show some moderate improvement over time but this seems to tip off and they start making less advantageous decisions (reward driven choices)
  • They get more tired as they are sleep deprived and start to make poor decisions
  • Triangle line: participants with composite of VM lesions and their general performance was worse overall and also showed that participants when they are sleep deprived they perform badly
  • Suggesting link to sleep deprivation and disadvantageous decisions
28
Q

Sleep Deorivation and Executive Function

A
  • Executive Functioning: A range of mental processes that allow us to inhibit impulsive actions, switch between tasks, and update plans
  • Executive Functions also depend on frontal brain regions, including the lateral and medial prefrontal cortex.
  • Evidence also suggests that very long periods of total sleep deprivation are associated with impaired executive functioning
29
Q

Does REM contribute to daytime alterness/sleepiness?

A
  • Nykamp et al. (1998). Sleep lab study with 26 healthy volunteers who were tested in a sleep lab over 5 consecutive days.
    • Night and Day 1: Screening
    • Night and Day 2: Baseline Sleep Measures
    • Nights 3&4, and Day 3&4: Deprivation of either REM sleep (experimental group) or non-REM sleep (control group)
    • Night and day 5: Recovery
  • Daytime sleepiness was measured using the Multiple Sleep Latency Test (MSLT).
  • People take 5 scheduled naps per day in the sleeping lab, separated by 2 hour blocks
  • Participants are only allowed to sleep for max 15 minutes per nap.
  • Latency to fall asleep is used as the dependent measure
  • Found:
    • Suggest that REM sleep doesn’t decrease daytime sleepiness, it doesn’t make people faster to fall asleep during scheduled naps, whereas this effect is present in those deprived in other stages of sleep
30
Q

Nykamp et al, (1998) - Traces of sleepiness and awakness

A
  • The awake and REM sleep look very similar suggesting that perhaps REM sleep is just as replenishing as being awake so it doesn’t have this rejuvenating quality that sleep does
  • In contrast, the EEG signal in non REM is particularly slow in terms of its frequency and high-end amplitude suggesting that its really this non REM sleep that is quite different from wakefulness rather than REM sleep
31
Q

Deafult theory of REM sleep

A
  • Theory: It is difficult/potentially dangerous to stay in slow-wave sleep (e.g., stages 3-4) for long periods of time.
  • To ease this difficulty, body switches to easier sleep stages (e.g. REM) or wakefulness periodically depending on our immediate needs
    • Could return to wakefulness
    • or REM sleep
32
Q

Xie et al. (2003)

A
  • Removal of toxic waste from the brain tends to happen in slow wave sleep
33
Q

Slow-wave sleep and sleeo deprivation

A
  • Slow-wave sleep is particularly protected when sleep duration is short
  • Short sleepers—people who sleep < 6 hours per night—tend to get as much slow-wave sleep as people who sleep longer
  • Reducing sleep time usually results in a reduction in sleep Stages 1&2, but not in slow wave sleep
  • Daytime naps after a full nights sleep typically do not involve much slow-wave sleep
  • Conclusion?
    • Sleep deprivation → increased sleep efficiency, where slow-wave sleep is prioritised.
    • Suggests that slow wave sleep might be particularly important/restorative
34
Q

Differences between long and short sleepers

A
  • Fichten et al. (2004)
    • Large sample of short and long sleepers (N = 239) Compared long (>8hrs) and short (<6hrs) sleepers on 48 dimensions:
      • Daytime sleepiness
      • Daytime naps
      • Stress & Anxiety
      • Busyness
      • Overall life satisfaction
    • And, Screened participants with potentially cofounding factors (e.g., illness, external stress)
    • Results: Long and short sleepers did not differ on any measure of health and wellbeing
    • Problems?
      • Correlational design means that other unaccounted for factors might explain the preserved health in short sleepers. Experimental interventions are needed
35
Q

Long-term reduction of nightly sleep - Webb and Agnew, (1974)

A
  • Volunteers (N=16)
  • Slept for 5.5 hours/night for 60 days
  • The completed extensive battery of mood, medical, and performance tests
  • Result: Only one slight deficit on a test of auditory vigilance
  • Small sample size
36
Q

Long-term reduction of nightly sleep - (Friedman et al., 1997)

A
  • Volunteers (N=8) reduced sleep over 9 weeks, then sustained a reduced sleep duration (4.5-5.5 hrs/night) over a year
    • Sleep efficiency increased over time in all participants (i.e., higher proportion of slow-wave sleep)
    • No deficits emerged on medical, mood, or performance tests as a function of reduced sleep over time
    • Consistent with the plasticity of sleep—sleep efficiency increases when less time is available to sleep
  • Problems? Sample sizes might limit generalizability.
37
Q

Long-term epidemiological study of sleep and health

A
  • Tamakoshi and Ohno (2004):
    • Tracked 104,010 volunteers over 10 years
    • Started with healthy sample (excluded those with ill-health, depression, significant stress)
    • Correlational → does not prove that sleeping > 8 hours is deadly.
    • Does indicate that sleeping 6-7 hours is not a significant health risk

Year 3 - Biological (9 decks)

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