EEG and Sleep

Question 1

What is EEG

Answer 1

non-invasive measurement of electrical brain activity 
relatively cheap
field potentials 20-100 uv
poor spatial resolution
good temporal resolution

Question 2

The MEG measure?

Answer 2

measures magnetic field generated by current flow

Question 3

EEG brain waves

awake waves? - ALPHA and BETA differences

Answer 3

normal awake individuals show:
intermittent bursts of synchronous 30-80Hz in sensory and motor regions, co-ordinating multiple pathways related to a common experience (eg. all aspects of a person)
ALPHA - eyes closed/ relaxed, 8-13 Hz (freq), 10-50uV (amplitude)
BETA - eyes open / aroused, 14-25Hz(freq)

Question 4

Wave origin
oscillations?
Feedback loop goes from where to where?

Answer 4

electrical activity in deep cortex is detected (few mms into brain, deeper signals missed)
cortico-thalamic oscillations (feedback loops oscillate)
feedback loops from cortex–>thalamus = waves detected
(oscillation is what gives the waves its up and down form)

Question 5

Regional variations in alpha rhythms
(3 types in 3 places)
mirror neurons?

Answer 5

α- in visual cortex
ϰ - α-like in auditory cortex
μ - α-like in sensorimotor cotex
mirror neurons= premotor neurons that also mimic seen movements

Question 6

θ rhythm (theta)

Answer 6

4-8Hz (lower frequency than alpha and beta)
early stage sleep
classical descriptions found:
-common in children
-common in frustrated adults
-used for detecting possible tumours in brain
recent descriptions found:
-linked to functions eg. spatial memory tasks
-hippocampal θ rhythms in memory

Question 7

Epileptic discharge

Answer 7

large, coordinated spread of electrical charge

Question 8

2 types of sleep?

when do stages become established in human?

Answer 8

cycles of REM and non REM sleep

stages appear in developing foetus at 24weeks

Question 9

Non-REM sleep

describe stages 1 - 4

Answer 9

1= α rhythm slows = drowsy (freq decreases and amplitude increases)
2= slowing and sleep spindles(bursts) = light sleep
3= slowing, no spindles transition to…
4= 𝛿(delta) waves - high amplitude, low freq <4Hz = deep sleep
(Body active sleep walking may occur)

Question 10

REM sleep

Answer 10

Beta rhythm, dream sleep, reduces with age, laying down of memories, deprivation = no effect/ irritability

Question 11

Role of sleep?

Answer 11

Restorative, loss evokes homeostatic breakdown in animals(can lead to cog. impairment), equivocal in humans(12days)

Question 12

Do androids dream?

Answer 12

mammals and young birds yes
adult birds, reptiles and amphibia - unknown
dolphin- half brain sleeps half doesn’t to prevent drowning

Question 13

Control of sleep
Brain regions associated?
Pineal gland secretes what?
NETs involved and levels in day?

Answer 13

reticular-activating system

• brainstem regions= neurons that use NETs - ACh, Adr, 5HT, GABA
• when awake- ACh, NA, 5HT used
• acetylcholine starts before REM
• norepinephrine and serotonin start as REM decreases
• -Hypothalamus:
• suprachiasmatic nucleus(SCN) =internal clock = important for circadian rhythem (endogenous)
• secretes hypocretin/orexin
• project to brain stem (transmitter systems here)
• low in narcoleptics (orexin v. low)
• -Cortex
• -Basal Ganglia
• -Pineal Gland
• secretes melatonin (which influences sleep)
• receives input from non-rod/cone retinal recpetors (inform about day length)
• secretion of melatonin varies with light levels (5HT during day), less light= more melatonin=sleep

Question 14

Sleep probability is a balance of S and C

What is process S and process C?

Answer 14

Process S = sleep/ energy debt
Process C = circadian rhythm(SCN)
These either promote or prevent sleep
(synchronised = sleep, not = problems eg.those felt by shift workers)