EEG and Sleep Flashcards
Normal awake individuals show with eyes closed…?
a rhythm 8-13 Hz
10 - 50 uV
Normal awake individuals show with eyes open…?
B rhythm 14-25 Hz
y rhythm, intermittent bursts of synchronous 30-80 Hz in sensory and motor regions
Where do the waves originate?
Deep cerebral cortexes (few mm in - deeper signals missed by EEG)
Why do EEGs show wave forms?
Due to cortico-thalamic feedback loops that oscillate
Reflects the interaction of inputs and outputs between the cortex and thalamus
What do the y rhythms in awake individuals represent?
Coordination of multiple pathways related to common experience, give an overall image of particular experience (smell, sounds, image etc.)
Where is the a rhythm from?
Visual cortex
What is k rhythm?
a-like rhythm in auditory cortex
What is the u rhythm?
a-like rhythm in sensorimotor cortex
contains mirror neurons that also mimic seen movements
ϴ rhythm
4-8 Hz Early stages of sleep Common in children Frustrated adults Possibly can detect brain tumours Linked to spatial memory tasks Hippocampal ϴ rhythm in memory
When do sleep stages develop in pregnancy?
24 weeks
Stage 1 sleep
a rhythm slows, become drowsy
Stage 2 sleep
Slowing and sleep spindles (bursts), light sleep
Stage 3 sleep
Slowing, no spindles
Stage 4 sleep
𝛿 waves, high amplitude, low frequency <4Hz, deep sleep
Role of sleep
Restore the body
What does lack of sleep do?
Evokes homeostatic breakdown in animals in weeks
Humans - 12 days OK
REM sleep
EEG like B rhythm
Typically dreaming
Reduces with age
Important for laying down of memories
What does deprivation of REM sleep cause?
No effect
Potentially irritability
What is special about dolphin’s sleep?
They only sleep with half of their brain at a time
Brain stem in sleep
ACh, adrenaline, 5-HT (serotonin), GABA involved
Hypothalamus in sleep
Suprachiasmatic nucleus (SCN)
Biological clock
Controls circadian rhythm
Secretes hypocretin/orexin (less in narcolepsy)
Which other regions are involved in sleep control?
Cortex
Basal forebrain
Pineal gland
Pineal gland in sleep
Secretes melatonin Influences sleep/wake cycle Non-rod/cone retinal receptor input Secretion varies with light level 5-HT during day Less light, more melatonin, sleep promotion
What is sleep probability a balance of?
Process S - sleep/energy debt
Process C - circadian rhythm (SCN)
