Conciousness

Question 1

two factors that dertemine conciousness

Answer 1

levels (alertness)

contents (subjective experience)

Question 2

what is involved in alertness?

what is its function?

Answer 2

reticular formation regulating vital functions projecting into the thalamus and cortex

controls where a sensory signals can reach the cortical sites of concious awareness e.g. posterior parietal cortex

Question 3

what make up the reticular activating system /RF?

Answer 3

1) Locus coeruleus (NA neurones) in the pons
2) Ventral tegmental area (Dopaminergic neurons)
3) raphe nucleus (serotoninergic neurones)
4) thalamic projections ( Cholinergic neurons)
- – these project into the cortex to increase activity via the thalamus to maintain awareness

Question 4

additional functions of the RF

Answer 4

CVS
resp
bladder
motor patterns

Question 5

what are all the sensory pathways that input into the RAS (so the brain stays awake)?

Answer 5

o Touch and pain – from ascending tracts.
o Vestibular – from medial vestibular tracts.
o Auditory – from inferior colliculus.
o Visual – from superior colliculus.
o Olfactory – from medial forebrain bundle.

Question 6

what are the RF efferents that modulate cerebral activity?

where are the neurotransmitters each of them use?

Answer 6

1) nucleus coeruleus
(neurones from pons into cortex) NORADRENALINE
2) ventral tegmental nucleus
(neurones from midbrain into cortex) DOPAMINE
3) raphe nucleus
(midline location brain and spinal cord) SEROTONIN
4) Thalmus: ACETYLCHOLINE
- thalamic relay nuclei to cortical areas
- intralaminar nuclei to all cortices
- reticular nuclei

Question 7

which of the RF nuclei has the most important role in regulating level of arousal (3 mechanisms)

Answer 7

the cholinergic neurones
· Excitation of individual thalamic relay nuclei –> activation of the cortex.

· Projections to intralaminar nuclei –> project to all areas of the cortex.

· Projections to the reticular nucleus –> regulates flow of information through thalamic nucleus to cortex

Question 8

The 4 waves of each level of conciousness/arousal

Answer 8

beta (13-30 Hz) - awake with normal conciousness
alpha (8-13 Hz) - relaxed/ eyes closed
theta (4-8Hz) - drowsiness
delta (upto 4Hz) -sleep

(gamma is hyperactivity like that seen in seizures)

higher frequencies are associated with creating concious contents in the focus of the mind’s eye via thalamocortical feedback loops (40Hz)

Question 9

what is a contusion of the head?

Answer 9

a bruise, localised bleeding within the brain

Question 10

what is a concussion?

Answer 10

diffuse, widespread homogenous impairment of brain tissue due to trauma

Question 11

what is delirium?

Answer 11

aka acute confusion
sustained disturbance of consciousness, mental processes are slowed, inattentiveness, disorientation or difficulty carrying out simple commands

Question 12

what is stupor?

Answer 12

lack of critical cognitive function and consciousness

only responsive to pain

Question 13

what is coma?

Answer 13

damage to RF/thalamus
unconsciousness where subject can not be roused by strong sensory stimuli
different to sleep as metabolic activity of the brain is depressed

Question 14

causes of coma

Answer 14

• metabolic alteration e.g. hypogylcaemia, hypoxia (outside brain)
• bilateral lesions in cerebral hemispheres
• lesions in thalamus or brainstem (with increased ICP)

Question 15

3 sections of GCS and scoring

Answer 15

eyes (1-4) 
veral response (1-5) 
motor response (1-6)

score range 3-15
score of 3 is severe brain damage and brain death

Question 16

what are the two forms of irreversible coma?

Answer 16

1) persistent vegetative state (cortex damage but RAS/RF intact)
2) brain death (brainstem damage)

Question 17

persistent vegetative state

Answer 17

irreversible coma due to disconnection of cortex from brainstem or widespread cortical damage

• brainstem still works therefore reflexes, postural movements and sleep-wake cycles may be present
• can eventually be aroused

Question 18

braindeath

Answer 18

due to brainstem death so body is kept alive artificially
treatment is ceased when there is apparent loss of brainstem reflexes and response to hypercapnia
- spinal reflexes and some postural movements may be present

Question 19

what is left visual neglect?

Answer 19

breakdown of consciousness awareness after right parietal damage
can follow as a result of stroke on the right hemisphere

Question 20

effect on vision in left visual neglect

Answer 20

the person remains unconscious of information from the left visual field despite the PVC being intact
parietal cortex damage means info does not reach awareness due to disrupted RF

Question 21

investigating visual neglect

Answer 21

• star cancellation test (patient cancels fewer stars on the side of the neglect)
• visual field: patient cant cross the midline

Question 22

what is used to study conciousness?

Answer 22

fMRI to assess covert awareness
brain activity pictured during certain tasks, certain areas are activating with information

e.g. tennis and house walk

Question 23

visual neglect vs hemianopia

Answer 23

hemianopia patients know that their visual field is restricted and adjust to the field

neglect patients makes them think they see see their whole field of vision when they actually cannot see half of it

Question 24

quantifying conciousness

Answer 24

Transcranial Magnetic Stimulation and EEG to create a pertubational complexity index

this followes the complexity of formed brainwaves

Question 25

coma vs VS

Answer 25

there is some wakefullness in vegetative state

Question 26

what is damaged in Locked-In syndrome?

Answer 26

ventral pons

stroke of the basilar artery