Introduction to Consciousness

Question 1

What is consciousness?

2 Factors important to classifying consciousness

Mechanisms of consciousness

Neural correlates of consciousness (NCC)

Answer 1

Processes that enable us to experience the world around us , aware and responsive to surroundings

Vigilance (awake behaviour, eyes open)
Awareness (level/contents of consciousness)

Dynamics of neuronal activity

The minimum neuronal mechanisms jointly sufficient for any one
specific conscious experience.
• Primarily localized to a posterior cortical hot zone that includes
sensory areas

Question 2

What structure within the brain is heavily involved in regulating alertness?

Answer 2

Reticular Activating System (this is part of reticular formation)

Question 3

Levels of arousal and awareness in each of the following:

• Normal consciousness
• Coma
• Vegetative state
• Minimally conscious state
• Locked-in-syndrome

Answer 3

-Normal consciousness
Max arousal and awareness
-Coma
Min arousal and awareness
-Vegetative state
Max arousal min awareness
-Minimally conscious state
Max arousal, REDUCED awareness
-Locked-in-syndrome
Max arousal and awareness

Question 4

The RF modulates cerebral activity via various projections. Where do these projections go to?
Which 2 other areas in the brain work in close relation with the RAS?

How to measure consciousness

Answer 4

From brain stem to thalamus, hypothalamus and cortex
Ventral tegmental area (dopaminergic neurones) (in midbrain)
• Locus coeruleus (noradrenergic neurones) (in pons)

Quantifying brain complexity using transcranial magnetic stimulation and EEG- pertubational complexity index PCI

Question 5

Which of these projections is most important in regulating the level of arousal?

What is used to monitor levels of arousal

Answer 5

Cholinergic projections

EEG rhythms

Question 6

What are the three mechanisms by which these projections regulate the level of arousal?

Answer 6

Excitation of individual thalamic relay nuclei –> activation of cortex
Projections to intralaminar nuclei –> project to all areas of cortex
Projections to reticular nucleus– regulates flow of information through other thalamic nuclei to the cortex

Question 7

What are the different waveforms seen on an EEG and what levels of arousal do they represent?

Answer 7

Delta (< 4 Hz) – seen in sleep
Theta (4-8 Hz) – drowsiness
Alpha (8-13 Hz) – subject relaxed with eyes closed –HEALTHY BRAIN
Beta (13-30 Hz) – normal waking consciousness
Gamma range (~40 Hz) – creation of conscious contents in the focus of the mind’s
Do The ABGs

Question 8

What is a cerebral contusion?

Answer 8

Localised bleeding in the brain (bruise in the brain)

Question 9

What is a concussion?

Answer 9

Diffuse, widespread, homogenous impairment of brain tissue due tobrain trauma

Question 10

What is acute confusion/delirium and stupor?

Answer 10

Acute confusion and delirium– sustained disturbance of consciousness where mental processes are slowed. Subject may be inattentive, disorientated and having difficulty carrying out simple commands or speaking
Stupor– lack of critical cognitive function and consciousness – only responsive to pain

Question 11

Damage to the reticular formation can lead to coma. What is a coma?

Answer 11

State of unconsciousness in which the subject cannot be roused even by strong sensory stimuli
Different from sleep – metabolic activity of the brain is depressed and there is total amnesia for this period

Question 12

State some causes of coma.

Answer 12

Metabolic

• Drug OD
• Hypogly
• Diabetes
• The failures
• Hypercalcaemia

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

Hemisphere lesion:

• cerebral infarct
• cerebral haemorrhage (sub or extradural)
• Abscess
• Tumour

Brain stem

• Brain stem infarct
• Tumour
• Abscess
• Cerebellar haemorrhage
• Cerebella infarct

Question 13

Describe how the Glasgow Coma Scale is structured.

Answer 13

MIN 3=severe brain injury and brain death
Eye opening = out of 4 
Verbal responses = out of 5 
Motor responses = out of 6
Max=15

Question 14

What causes a persistent vegetative state?

Answer 14

Disconnection of the brainstem from the cortex or widespread cortical damage
Brainstem is still functioning so reflexes, postural movements and sleep-wake cycle may still be present

Question 15

What is brain death?

Answer 15

Irreversible coma due to brainstem death, but body kept alive artificially
NOTE: spinal reflexes and some postural movements may be present

Question 16

What would the consequences of a right parietal lesion be?

Answer 16

Hemispatial neglect – the patient will not pay attention to the left visual field
Information from the left visual field is reaching the primary visual cortex but because of the parietal damage, the patient is not conscious of this visual field

Question 17

What imaging technique can be used to study consciousness in health and disease?

Answer 17

Functional MRI

Question 18

What is blindsight?

Answer 18

Brain-damaged (occipito-visual cortex) patients who are perceptually blind of their visual field can demonstrate some responses to visual stimuli e.g. manually interacting with ‘unseen’ objects and avoiding ‘unseen’ objects

Question 19

Diffuse axonal injury

Answer 19

Damage to white matter tract– telephone cables

Copus callosu,

Question 20

Posteriorr fossa lesion

Answer 20

Compress brain stem