EEG and Sleep

Question 1

Normal awake individuals show with eyes closed…?

Answer 1

a rhythm 8-13 Hz

10 - 50 uV

Question 2

Normal awake individuals show with eyes open…?

Answer 2

B rhythm 14-25 Hz

y rhythm, intermittent bursts of synchronous 30-80 Hz in sensory and motor regions

Question 3

Where do the waves originate?

Answer 3

Deep cerebral cortexes (few mm in - deeper signals missed by EEG)

Question 4

Why do EEGs show wave forms?

Answer 4

Due to cortico-thalamic feedback loops that oscillate

Reflects the interaction of inputs and outputs between the cortex and thalamus

Question 5

What do the y rhythms in awake individuals represent?

Answer 5

Coordination of multiple pathways related to common experience, give an overall image of particular experience (smell, sounds, image etc.)

Question 6

Where is the a rhythm from?

Answer 6

Visual cortex

Question 7

What is k rhythm?

Answer 7

a-like rhythm in auditory cortex

Question 8

What is the u rhythm?

Answer 8

a-like rhythm in sensorimotor cortex

contains mirror neurons that also mimic seen movements

Question 9

ϴ rhythm

Answer 9

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

Question 10

When do sleep stages develop in pregnancy?

Answer 10

24 weeks

Question 11

Stage 1 sleep

Answer 11

a rhythm slows, become drowsy

Question 12

Stage 2 sleep

Answer 12

Slowing and sleep spindles (bursts), light sleep

Question 13

Stage 3 sleep

Answer 13

Slowing, no spindles

Question 14

Stage 4 sleep

Answer 14

𝛿 waves, high amplitude, low frequency <4Hz, deep sleep

Question 15

Role of sleep

Answer 15

Restore the body

Question 16

What does lack of sleep do?

Answer 16

Evokes homeostatic breakdown in animals in weeks

Humans - 12 days OK

Question 17

REM sleep

Answer 17

EEG like B rhythm
Typically dreaming
Reduces with age
Important for laying down of memories

Question 18

What does deprivation of REM sleep cause?

Answer 18

No effect

Potentially irritability

Question 19

What is special about dolphin’s sleep?

Answer 19

They only sleep with half of their brain at a time

Question 20

Brain stem in sleep

Answer 20

ACh, adrenaline, 5-HT (serotonin), GABA involved

Question 21

Hypothalamus in sleep

Answer 21

Suprachiasmatic nucleus (SCN)
Biological clock
Controls circadian rhythm
Secretes hypocretin/orexin (less in narcolepsy)

Question 22

Which other regions are involved in sleep control?

Answer 22

Cortex
Basal forebrain
Pineal gland

Question 23

Pineal gland in sleep

Answer 23

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

Question 24

What is sleep probability a balance of?

Answer 24

Process S - sleep/energy debt

Process C - circadian rhythm (SCN)