Sleep, brain rhythms and EEG

Question 1

What two key factors are considered in diagnosing disorder based on electrical activity

Answer 1

1. region of electrical activity

2. Behaviour person undertaking e.g. if asleep brain activity has a particular rhythm which may be disordered in disease

Question 2

Describe how an EEG works

Answer 2

• place electrodes on the skull surface
• electrodes measure collective activity of many surface neurons usually pyramidal neurons
• when the neurons active in the same manner this synchronous activity will leader to a higher intensity on the EEG

Question 3

What is the major limitation of EEGs

Answer 3

Only surface neurones so cannot give indication of the deeper structures of the brain such as thalamus or brainstem

Question 4

What two basic factors do we look at on an EEG

Answer 4

The intensity of signal
The rhythm of activity
Which we compare this to other regions of the brain

Question 5

What normal situations will you see an increase in intensity of an EEG

Answer 5

Increase in intensity of an EEG is due to an increase in synchronous activity

This can occur in:

1. In normal cognition
   - This is used as basis for optical illusions where when when found solution to illusion never tricked again as got synchronous activity of fast gamma oscillations where neurones working together in different parts of brain
   - Hence linked to perception
2. Sleep:
   - When you go through awake state to sleep state synchronisation increases, indicated by larger intensity of signal (large peaks) and even through phases of sleep the synchronisation increases

Question 6

What are the three classifying factors of sleep

Answer 6

we can classify sleep by what you observe which is decreased mobility (don’t physically move as much), less responsive to sensory input and as a result the cortex is less excited

Question 7

Define sleep and why is it different to a coma

Answer 7

sleep is a “a readily reversible state of reduced consciousness”

A coma is not reversible because you cannot be aroused when in a coma, you can be woken up from sleep

Question 8

What are 4 benefits of sleep and how were they discovered

Answer 8

Benefits:

• lack of sleep can impair mood and cognition
• escape predators
• cell repair
• conserve energy

we know it is important to health as all animals do it and if disrupted can lead to decreased health VICE VERSA so too much sleep issue as well.

Also, the extremes of age tend to sleep longer, so got some importance

Question 9

Describe the different rhythms in awake state and through stages of sleep

Answer 9

Awake: alpha and beta rhythms 
REM: beta rhythms 
Stage 1: theta rhythms 
Stage 2: theta + spindles + K complexes 
Stage 3: delta rhythms 
Stage 4: >50% delta rhythms 

stages numbered are of non- REM sleep

Question 10

How can we distinguish REM sleep from the awake state and why is this difficult based on EEG

Answer 10

Distinguish based on:
- rapid eye movements key feature based on where the oculomotor nerve leaves brainstem ( at mid-brain superior colliculus)
- it different to active as the brainstem is largely inhibited so that have decreased muscle tone so don’t act out dreams
Difficult as beta rhythms only in REM sleep which is one of the rhythms seen when active, and shows desynchronised activity indicated by small peaks in EEG similar to when awake.

Question 11

What stages of sleep do dreams occur

Answer 11

All of them the idea it is just in REM sleep is a myth

Question 12

What is a hypnogram and state its three key findings

Answer 12

Hypnogram is a graph which tracks stages of sleep you in with time

1. as you sleep you progress down each stage of sleep then back up in a cycle
2. As you continue sleeping you go back up the stages at a lower stage e.g. first cycle go to stage 4 but second cycle may go up at stage 3 to stage 2. This means the deepest sleep occurs at the start of sleeping
3. As you increase time of sleep the time in the REM stage gets progressively longer most likely as getting ready to be aroused

Question 13

What is arousal and what causes you to be aroused from sleep

Answer 13

Arousal is sensory arousal where wake up from sleep and is due to the reticular activating system

Question 14

Describe the reticular activating system and how it links to arousal

Answer 14

The reticular activating system represent a group of neurons

These neurons can be split into those using ACH as a neurotransmitter and those using amines as a neurotransmitter i.e. aminergic neurons

the activation of aminergic neurons allow the cortex to receive sensory information from the thalamus and the acetylcholine neurons allow the thalamus to receive sensory information from the brainstem

As long as these neurons are allowing sensory information to be received by the thalamus and transmitted to the cortex you will be aware of sensory stimuli and so awake

Question 15

What is state of RAS in the REM sleep

Answer 15

REM sleep is similar to the awake state as the ACH neurotransmitters are firing but the aminergic aren’t so you are asleep

In addition, the descending pathways inhbited in the brain stem by RAS so have decreased muscle tone

Question 16

What drugs can make you sleepy and how has this changed its manufactures

Answer 16

Antihistamines can oppose the activity of aminergic neurones using histamine as neurotransmitter because they are histamine receptor antagonists

to counter this issue use forms of antihistamines which cannot cross BBB and so get into the brain

Question 17

What changes in the RAS and other parts of brain take you down stages of sleep from REM

Answer 17

In non REM sleep get decreased activity of both ACH and aminergic neurones in RAS

Also get INCREASED activity of the VPLO which are a group of neurones in the hypothalamus which help bring you down through stages of sleep

Question 18

Is sleep due to the absence of activation of RAS

Answer 18

No as in non REM sleep get INCREASED activity of the VPLO which are a group of neurones in the hypothalamus which help bring you down through stages of sleep

Question 19

Describe the flip flop theory

Answer 19

It is the idea that as sleep is active process it is a balance of factors than merely the absence of activation of RAS that causes you to be in sleep state rather than wake state

it is like on see-saw and depending on factors can be pushed to one state or another, these factors include adenosine, circadian rhythm and physical activity as well as others

this makes sense as REM sleep is very similar to wake state but shift of certain other factors puts you more to sleep state than wake state

Question 20

What 3 main factors induce sleep

Answer 20

1. waking time which is like clock ticking down from once awake so when awake for too long at certain point will induce sleep this is mediated by adenosine
2. physical activity
3. circadian rhythm

Question 21

Why does caffeine keep you awake

Answer 21

It inhibits action of adenosine involved in determining waking time as caffeine is an adenosine receptor antagonist

Question 22

Describe the formation of circadian rhythm

Answer 22

the suprachiasmatic nucleus (SCN) =
‘body clock’ and drives the natural circadian rhythms by breakdown and synthesis of proteins it is like clock ticking

retinal input can reset this is known as zetigeber (giving of time)

Question 23

State 4 clinical links to circadian rhythm

Answer 23

1. jet lag
2. shift workers
3. chronotherapeutics when to give drugs if want in night day or mid-day depending on your circadian rhythm e.g. cortisol levels highest in morning

Question 24

hypnogram in depression and schizophrenia what are key features

Answer 24

no stage 3 and 4 sleep

REM is longer and not gradually increasing as night goe son

Question 25

Describe deep sleep disorders

Answer 25

More in childre lead to sleep walking, night terrors and bedwetting

should correct self

Question 26

Describe REM disorder and what disease linked to

Answer 26

Loss of inhibition by brainstem to muscle tone
so act out on dreams
linked to parkinsons

Question 27

Describe narcolepsy and link to obesity

Answer 27

Suddenly flop from sleep to wake states and loose muscle tone (cataplexy)
orexin(hypocretin) in lateral hypothalamus and promotes RAS activation
orexin linked to feeding so link to obesity
so less orexin less regulation of RAS so just flip flop from awake to sleep rapidly
as less orexin must be that orexin helps with feeling of satiety

Question 28

Describe basis of use of sleep as a phobia therapy or CBT and depression

Answer 28

sleep promotes learning and memory
so in natural disasters where sleep deprived don’t form traumatic memories as easily
use in therapy as after positive therapy/ CBT sleep so reinforces the knowledge
deprive people of sleep some don’t show depression

Question 29

Describe some types of sleep disorders and why hard to define insomnia

Answer 29

sleep apnoea 
insomnia 
- hunger 
- 5-HT depletion 
- withdrawal from hypnotics 
-illness 
depression

hard to define insomnia as individual hypnogram varies