Chapter 6: The ultimate test

Question 1

Quadriplegic

Answer 1

Paralysed on all four limbs

Question 2

Coma

Answer 2

Prolonged loss of capacity to awaken for over an hour
- patient is completely unresponsive with eyes closed and no signs of awareness

Question 3

Brain death

Answer 3

Complete absence of brain stem reflexes, inability to start breathing and flat EEG
- diagnosed within 6-24hrs once hypothermia and intoxication are ruled out

Question 4

Vegetative state

Answer 4

Physical state with no social interactions or intellectual activity
- occasional slow, involuntary movements
- only affects upper brain, autonomous nervous system intact
- sleep-wake cycle present

Question 5

Persistent and permanent vegetative states

Answer 5

Persistent vegetative state declared after 4 weeks

Permanent vegetative state declared after 6 months (if not traumatic) or 12 months (if traumatic)

Question 6

Minimally conscious state

Answer 6

Voluntary control over certain actions during some periods
- may respond using blinking or nodding
- expressions appropriate to context

Question 7

Coma Recovery Scale

Answer 7

Assesses simple functions to improve reliability of diagnoses of minimal consciousness
- repeated at multiple times of the day

Question 8

Locked-in syndrome

Answer 8

Patient is fully aware and conscious but is almost completely paralysed (save some eye movements)

• lesions to lower brain and brain stem
• thalamus and cortex usually intact
• diagnosed after 2.5 months on average
• consciousness usually detected first by family members

Question 9

Superior and middle temporal gyrus

Answer 9

Hearing and speech comprehension

Question 10

Supplementary motor area

Answer 10

Planning of movements

Question 11

Which areas are related to the representation of space?

Answer 11

• parahippocampal gyrus
• posterior parietal lobe
• premotor cortex

Question 12

Mismatch negativity

Answer 12

Large auditory cortical negative voltage in response to deviances
- can occur unconsciously
- only during local mismatches and deviations (beep-beep-boop)
- P3 wave activates during global mismatches (3x beep-beep-boop, 1x beep-beep-beep)

Question 13

Sensitivity and specificity

Answer 13

Sensitivity = (true positive / positive truth)
Specificity = (true negative / negative truth)

Question 14

Did patients who were stimulated by TMS react in EEG?

Answer 14

Yes, not only conscious patients showed global and complex activity when cortex was stimulated but also vegetative patients who then became minimally conscious

Question 15

Which areas are associated with decreased activity when consciousness is lost?

Answer 15

• bilateral prefrontal regions
• parietal regions
• cingulate
• precuneus

Question 16

Weighted symbolic mutual information

Answer 16

Measures how much information is shared between two sites
- especially long distance connections are strongly reduced

Question 17

Schiff et al. (2007)

Answer 17

They implanted electrodes into a minimally conscious patient’s central thalamus. His eyes opened and had an increased heart rate when stimulated. These behaviours disappeared when turned off but not to baseline level

Question 18

Potential causes of loss of consciousness

Answer 18

• death of prefrontal cortex neurons
• loss of connections between intact neurons
• circulating information becomes insufficient for a maintained state of activity

Question 19

Dopamine circuit stimulation

Answer 19

There are cases of a sleeping pill (Ambien) being able to revive consciousness in patients with akinetic mutism and aphasia, perhaps by inhibiting overexcited inhibitory receptors in the pallidum