Brain Rhythms: ECG, Sleep and Diurnal Rhythm

Question 1

-

Answer 1

region of the brain
behaviour
- electrical activity changes in certain regions during certain behaviours
- there is constant resting activity, the brain is never silent

Question 2

What does the EEG actually recording?

Answer 2

• cortical pyramidal (excitatory) neurones located near to the surface
• each electrode collects activity from a group of neurones
• synchronous activity of neurones producing larger waves

Question 3

What does each line on an EEG recording represent?

Answer 3

each line is an electrode

• different electrodes record different things
• each electrode changes over time
• there is varying electrical activity over time and space §

Question 4

What makes neurones fire synchronously?

Answer 4

• Thalamic neurones are the pacemakers
• Similar to SAN in that the cells are set up to produce AP one after the other and therefore fire continuously
• ## This creates the intrinsic rhythm of the brain

Question 5

What does synchronous firing in normal cognition allow us to do? What does it look like on an EEG?

Answer 5

Very fast (gamma) oscillations 
Allows perception e.g. binding phenomenon in dog picture

Question 6

Describe the differences in EEG activity during rest, thinking and sleep/

Answer 6

Rest = alpha waves 
Thinking = beta waves
Sleep = that and delta waves, longer and higher amplitude, increase in synchronous activity

Question 7

• -

Answer 7

• decreased mobility
• decreased responsiveness to sensory inputs
• decreased cortical excitability

Question 8

What is the simple definition of sleep?

Answer 8

A readily reversible state of reduced consciousness

Question 9

What kind of behaviour is sleep described as?

Answer 9

It is a motivated behaviour like eating

i. e. it is not a reflex (stereotype or characteristic)
- responding to a need
- changes over time - learning, external cues

Question 10

What are the functions of sleep?

Answer 10

• quantity and quality
• impairment of cognitive performance e.g. memory and learning
• decreased mood
• altered physical health e.g. metabolic, immune

Question 11

What are the stages of sleep?

Answer 11

Non-REM sleep:
- stage 1
- stage 2
- stage 3
- stage 4
REM sleep

Question 12

What are the characteristics of REM?

Answer 12

• desynchronised EEG activity
• rapid darting eyes
• easily aroused by meaningful stimuli
• when awakened appear alert and attentive
• dreaming, loss of muscle tone

Question 13

Increased activity of the thalamus leads to

Answer 13

increased synchronous activity

Question 14

Describe the EEG characteristics of each stage of sleep

Answer 14

REM
Non-REM:
1 = theta
2 = theta, spindles and K complexes
3 = delta
4 = <50% delta

Question 15

What are the characteristics of a normal hyponogram?

Answer 15

Sleep cycles though the 5 stages (NonREM 1-4 –> REM)
REM duration increases through the night
Brief awakenings during each REM sleep
Decrease stage 4 frequency through the night

Question 16

Which stage of sleep is considered deep sleep?

Answer 16

Non-REM stage 4

Question 17

What is the neural basis of wakenfulness/sleep? Is there an anatomical ‘sleep/wake’ centre?

Answer 17

reticular activating system --> arousal
Wakefulness 
--> ACh and aminergic neurones in thalamus --> relay sensory information to the cortex 
REM sleep
--> no aminergic activity 
--> also paralysis promoted 
Non-REM sleep 
--> absence of ACh and amine activity 
--> VLPO also leads to sleep

Question 18

What is the flipflop theory?

Answer 18

wakefulness and sleep are balanced

not a gradual transition between the two

Question 19

What factors affect sleep and wakefulness?

Answer 19

waking time - affected by caffeine
physical activity - sleep earlier but not more
circadian rhythm = suprachiasmatic nucleus, retinal input, neurones ‘tick’, protein synthesis and degradation allows time keeping

Question 20

What are the causes of insomnia?

Answer 20

• hunger
• 5-HT depletion - dietary factors
• withdrawal of hypnotics - rebound insomnia
• illness
• depression (increased REM and enter REM more easily)

Question 21

Give some examples of deep sleep disorders?
Who do they affect the most?
How are they resolved?

Answer 21

Sleepwalking, bedwetting, night tremors
Most prevalent in children
Self-curing

Question 22

What is REM sleep (behavioural) disorder?

Answer 22

uncommon disorder, most prevalent in men
decreased loss of muscle tone
act out dreams during REM sleep
precursor to Parkinson’s?

Question 23

What is narcolepsy?

What is thought to be the cause?

Answer 23

uncontrollable entry into sleep
cataplexy - loss of muscle tone
Cause: destruction of lateral hypothalamus, contains neurones that produce orexin/hypocretin, its role is to stabalise wakefulness
- defective flip-flop

Question 24

Can sleep be used as a therapy?

Answer 24

Sleep promotes learning and memory

• sleep deprivation in order to decrease traumatic memories
• phobias, sleep soon after non-traumatic exposure