Conciousness

Question 1

Definitions of consciousness

Answer 1

• Definitions are difficult
– the subject experience of the mind and the world around us
– that there is “something it is like” to be in the state of the subjective or first-person point of view
– the state of being aware of and responsive to one’s surroundings

Question 2

What are the 2 components of consciousness?

Answer 2

• vigilance (awake behaviour, eyes open)

- awareness (level/contents of consciousness)

Question 3

What are the mechanisms of consciousness?

Answer 3

RAS

• The reticular formation (RF) regulates many vital functions. The degree of activity in the reticular system is associated with alertness/levels of consciousness
• RF projects to the hypothalamus, thalamus and the cortex
• Ventral tegmental area (dopaminergic neurones) (midbrain)
• Locus coeruleus (noradrenergic neurones) (pons)

• The location of neurons?
• The number of neurons?
• The dynamics of neuronal activity
-> integration and differentiation

=> there is no single brain region for consciousness.

Question 4

NCC

Answer 4

Neural correlates of consciousness (NCC)
• The minimum neuronal mechanisms jointly sufficient for any one specific conscious experience.
• Primarily localized to a posterior cortical hot zone that includes sensory areas (Koch et al., 2016)

Question 5

What are some disorders of consciousness?

Answer 5

• coma
• vegetative state (destruction of cortex and hemispheres)
• minimally conscious state

NOT locked-in-syndrome(damage to pons) or brainstem death (irremediable damage to brainstem)

Question 6

Visual neglect

Answer 6

• there is no problem with vision
• the person no longer perceives half of reality
• higher order problem than visual defect

Question 7

How is level of arousal monitored with EEG?

Answer 7

• different waves at different levels of arousal
• delta are slowest (e.g. sleep)
• theta 4-8 Hz
• alpha = good, healthy brain around 10Hz
• gamma is higher
• slowing in an eeg is bad (theta or delta)
• loss of alpha rhythm is disease (theta and then delta)
• higher frequency neural oscillations are associated with the creations of conscious contents in the focus of the mind’s eye via thalamiocortical feedback loops.

Question 8

How can you assess coma / consciousness?

Answer 8

Glasgow Coma scale
3 points = dead
15 points = healthy

-> look at eyes, verbal response and motor response, 1-5 points possible in each.

Question 9

What are some causes of coma?

Answer 9

Metabolic
– Drug overdose – hypoglycaemia – diabetes
– “the failures”
– hypercalcaemia

Diffuse intracranial
– head injury
– meningitis – SAH
– encephalitis – epilepsy
– hypoxic brain injury

Hemisphere lesion
– cerebral infarct
– cerebral haemorrhage
• subdural
• extradural – abscess
– tumour

Brain stem
– brainstem infarct
– tumour
– abscess
– cerebellar haemorrhage
– cerebellar infarct