NEURO Sleep Dreaming and Circadian Rhythms Flashcards
(19 cards)
Why do we need sleep?
-Recuperation theories:
-> sleep is needed to restore homeostasis.
-> wakefulness causes a deviation from homeostasis.
-Adaption theories:
-> sleep is result of an internal timing mechanism.
-> sleep evolved lying still stops predators seeing you move.
What are circadian rhythms?
Endogenous and persistent with environment cues.
Modulated by external timing cues- ‘zeitgebers’.
Adapt the rhythm the rhythm to the environment. E.g phone, blue light.
What does the hypothalamus do?
Controls body temperature, hunger, thirst and circadian cycles.
What is the suprachiasmatic nucleus (SCN) of the medial hypothalamus?
Major internal clock is the suprachiasmatic nucleus (SCN) of the medial hypothalamus. Lesions to suprachiasmatic nucleus regulate timing of sleep. Not responsible for sleep itself.
Outline deprivation studies with lab animals?
Rats deprived of sleep.
When EEG they are attached to shows they are asleep, chamber floor moves- if rat does not awaken, it falls into water. Rats typically die after several days. Post mortem studies reveal extreme stress experienced by the experimental rats.
(BUT hard to separate effects of stressor used to prevent sleep with loss of sleep)
Outline sleep cycles?
Sleep consist of non-REM and REM sleep (REM Rapid Eye Movement).
Sleep defined behaviourally as: reduced motor activity.
Reduced response to stimulation.
Stereotypic posture (eye closed in humans).
Physiological activity can be conveniently measured using electrical recordings.
Muscle movements with electromyography.
Eye movements with electro-oculography.
Brain activity with electroencephalography (EEG).
What are the sleep stages?
Stage 1: transition between wakefulness and sleep, muscles are still active the eyes show slow, gentle, rolling movements, some theta activity.
Stage 2 + 3: sleep get deeper and deeper; the EEG gets progressively lower in frequency and higher in amplitude.
Stage 4: deepest stage of sleep, reached in less than an hour and continues for up to half an hour, characterised by relatively high amplitude (delta) EEG activity.
REM (Rapid Eye Movement) sleep: the EEG looks like that of person who is awake and active although EMG is generally quiet. - Activity frequency slows the further down (more asleep) you get.
What evidence do we have that the reticular activating system is involved in sleep?
Cats with midcollicular transection displayed pattern of continuous slow-wave-sleep in their cortical EEGs.
Lesions at midcollicular level that damaged core of reticular formation, left the sensory fibres intact, produced cortical EEG indicative of continuous slow-wave sleep.
Electrical stimulation of the pontine reticular formation desynchronized the cortical EEG and awakened sleeping cats.
Cats with transection of the caudal brain stem (i.e. an encephale isole preparation) displayed a normal sleep-wake cycle of cortical EEG.
What is the reticular formation?
Set of interconnected nuclei located throughout the brain stem.
Reticular formation not anatomically well defined cause it includes neurons located in different parts of the brain.
Pontine reticular formation is part of pontine reticular formation a brain region without clearly defined borders in centre of pons.
What happens after sleep disruption?
Little effect of sleep deprivation:
-logical deduction, critical thinking.
-physical strength and motor performance.
Larger effect of sleep deprivation: effects executive function in prefrontal cortex.
-assimilating changing information.
-updating plans and strategies.
-innovative, lateral, insightful thinking.
-reference memory.
Outline experimental studies of sleep deprivation in human?
loss of 3-4hrs in one night:
-increased sleepiness.
-disturbance displayed on written tests of mood.
-poor performance on tests of vigilance.
2-3 days of continuous deprivation.
-experience of microsleeps, naps of 2-3 seconds.
How does sleep deprivation effect sleep efficiency?
Increases sleep efficiency.
After sleep deprivation, most lost stage 4 regained and SWS is increased.
Short sleepers get as much SWS as long sleepers.
Naps without SWS don’t decrease nights sleep.
Gradual reduction in sleep time led to decrease in stages 1 + 2.
Little sleepiness produced with repeated REM awakening unlike SWS.
What happens when you wake people in REM?
-proceed rapidly into REM as REM deprivation increases.
-REM rebound- more time in REM when deprivation is over.
-REM rebound suggests that REM sleep serves a special function.
How does REM contribute to the processing of explicit memories?
Processing explicit memories- but findings inconsistent.
-Antidepressant REM- blocking drugs do not interfere with memories.
-Default theory: difficult to remain in NREM sleep.
-REM- blocking drugs can cause periods of wakefulness.
How much does the brain develop during REM at different life stages?
70% REM new-born
30% REM new-born
22% REM adulthood
15% REM late adulthood
Why do we dream?
80% of awakenings from REM yield report of story-like dreams.
Dreams run on real time incorporating external stimuli- sleep walking + talking less likely.
NREM dreams isolated experiences such as falling.
Outline the interpretation of dreams according to Freud?
Freud explains: dreams triggered by unacceptable repressed wishes.
-> Manifest dreams- what we experience.
-> Latent dreams- underlying meaning.
What is activation synthesis?
Modern synthesis- alternative to Freud’s explanation of dreams.
Dreams due to cortex’s attempts to make sense of random brain activity (Hobson, 1989).
How does sleep link to clinical psychology?
Depression- associated with insomnia + hypersomnia.
Total sleep deprivation (TSD) for one whole night depressive symptoms in 40-60% treatments. Still unknown how sleep deprivation works.
