lecture 23: sleep Flashcards
mearuing sleep
EEG: record brain wave activity
EMG:record muscle activity
EOG: record eye movements
electrooculogram
records eye movements
measures dipole activity- front (+) vs back (-) of eyeball
waking state (beta)
EEG: beta waves, small amplitude waves with fast frequency
EMG: muscle tone, contract to some degree
EOG: eyes move
waking state (alpha)
larger amplitude and slower waves
awake but relaxed, with eyes closed
generated around occipital cortex
N1 sleep (drowsy state: sleep onset)
EEG: mixed waveforms, some slower (theta)
EMG: muscles have tone
EOG: eye rolling
N2 sleep (asleep)
EEG: stable theta waves with sleep spindles and K-complexes
EMG: muscles have tone
EOG: not moving
N3 sleep (deep sleep)
difficult to arouse, groggy, quick return to sleep
EEG: delta waves: large amplitude slow waves
EMG: muscles have tone
EOG: not moving
R sleep (REM)
EEG: same as waking, beta waves
EMG: muscles have no tone (atonia)
EOG: rapidly moving
how long do these cycles last
several sleep state changes in roughly 90 min periods
NREM dominates early, REM domintates later
- adults who sleep 8 hours spend 2 hours with REM
- infants spend half time in REM
dreaming
vivid dreams occur during REM, NREM are less vivid
- get longer throughout a sleep session
- a number of times each night, most people forget
psychoanalytic theories on what we dream about
sigmund freud: dreams are symbolic fulfillment of unconscious wishes
manifest content: loosely connected, latent: true meaning
Carl jung: dreams are expressions of collective unconscious
what do we dream about
most dreams related to recent events and ongonig problems
- 64% associate with negative emotion
18% associate with positive emotion
bottom up
dreams as meaningless brain activity:
activation synthesis –> cortex bombarded with signals from brainstem producing pattern of waking EEG so generates images, actions and emotions
fragmented without external verification, frontal activation is suppressed which suppresses memory/attention
top down: dreams as coping strategy
coping hypothesis: dreams highly organized and biased toward threatening images, important because lead to enhanced performance in dealing with life events
what does sleep accomplish
3 possibilities: biological adaptation, restorative process, memory mechanism
- sleep is not passive process
sleep as a biological adaptation
energy conserving strategy: gather food at optimal times and sleep to conserve energy
- animals with nutrient rich diet spend less time foraging for food and more time sleeping
- predatory animals sleep more than prey
exceptions to sleep as a biological adaptation
opossums: herbivores but sleep excessively
may have specialized energy conservation
sleep as a restorative process
we are tired at the end of day but feel refreshed with suffecient sleep
- chemical events that provide energy to cells may be reduced during waking and replenished during sleep
sleep deprivation studies
no lasting physiological effects (up to 18 days)
- decreases cognitive performance that require attention
microsleep is a confounding factor
REM sleep deprivation
wake up subjects when they enter REM sleep
- increased tendency to enter REM sleep
- REM rebound: spend more time in REM in first available session
3 phases of memory storage
- encoding (labile): new memory encoded, fragile and easily lost
consolidation: relatibely permanent representation of memory solidifed
recall: neural networks that represent memory area ctivated for use
- sleep solidifies and organizes memory
3 theories of sleep and memory storage
multiple process: different memories stored in different sleep states ex. facts in N sleep, motor in R sleep
Sequential process: memory manipulated in different ways during different sleep states, refined in N sleep stored in R
storage process: brain regions handle different kinds of memory during waking continue to do so during sleep
NREM and explicit memory consoldiation
recordings from 100 place cells in 3 conditions: NREM, food search, NREM after food search
- NREM sleep after food search correlated activity of place cells
REM and implicit memory consolidation
PET imaging to record brain activity while performing serial reaction time task
- sleep imaging revealed brain regions active during task are active during REM
therefore subjects may be dreaming about what they learned, REM sleep strenghtens memory
