L14: Consciousness

Question 1

define consciousness

Answer 1

The state of being aware of and responsive to one’s surroundings” – OED

Question 2

name some input and output Requirements of Human Consciousness

Answer 2

Arousal
Input:
-Sense organs
-Proprioception
-Interoception
-Emotion

Output / Control:
Motor-
Speech
Locomotion
Dexterity

Cognitive:
-Differentiation of awareness – naming, defining, recognizing unique features

-Integration of awareness –categorising, semantics, binding of experience

Emotional system:
-Drive /Instinct – to perceive, think and act

-Sensory – subjective experience of emotion

Question 3

what are some physiological and pathological states of consciousness

Answer 3

Sleep

Coma

Death

PVS

MCS

Locked in Syndrome

Question 4

describe the state of sleep

Answer 4

Decreased arousal:
-(and hence awareness & therefore cosiousness)

Physiological

Active process

Reversible & Cyclical

Question 5

Go over waves that represent:

1-slow wave sleep

2- stage 2 sleep

3- REM sleep

Answer 5

how was it

Question 6

describe the state of the coma

Answer 6

Characterised by complete loss of wakefulness and reactivity

A state of unresponsiveness to external stimuli with eyes closed

Pathological but usually reversible

Prolonged Unconsciousness

Question 7

what are the causes of a coma

Answer 7

Causes:

• Sedation / anaesthesia
• Epilepsy
• Electrolyte / metabolic disturbance
• Disturbance of thermoregulation

Structural damage to brainstem / thalamus / cortex

Stroke

Trauma

Tumour

Inflammation

Infection

Question 8

what are some causes of a metabolic coma

Answer 8

hepatic

uraemia

diabetic

pancreatic

adrenocorticoid failure

Question 9

what are the 3 outcomes of a coma

Answer 9

Reversal and recovery

Survival into vegetative state or minimally conscious sate

Irreversible cessation of function of:

1-Brainstem (brainstem death)

2-Cerebral cortex (neocortical death)

3-Body

Question 10

describe the Glasgow coma scale

Answer 10

slide 16

Question 11

what is the cause of the vegetative state (“Awake but Unaware”)

Answer 11

widespread damage to cerebral cortex (esp anoxia, head injury) – Neocotical Brain death

Question 12

describe the vegetative state

Answer 12

Absent awareness (& hence consciousness)

Preserved arousal (preserved sleep/wake cycle)

No voluntary response to environment

Variably preserved reflex responses to environment

Question 13

what are the 2 categories of the vegetative state

Answer 13

Persistent/continuing Vegetative State >4 weeks

Permanent Vegetative State:

• After a non-traumatic Brain Injury
• –6 months in the UK

—After Traumatic Brain Injury
1 year

Question 14

describe UWS

Answer 14

Unresponsive wakefulness syndrome’ (UWS)

Proposed by the European Task Force on Disorders of Consciousness

Yet to be fully defined.

Question 15

describe the minimally conscious state

Answer 15

Like Vegetative State, but with at least one of 11 items:

1-consistent movement to command

2-reproducible movement to command

3-object recognition

4-object localization

5-reaching

Question 16

describe emergence from MCS

Answer 16

Emergence from MCS signaled by at least one of 2 items:

• functional communication
• object use.

Question 17

what do we use the The Coma Recovery Scale - Revised (CRS-R) to distinguish

Answer 17

• distinguish VS/UWS from MCS

Question 18

how can we Detect for Awareness in

the ‘Vegetative State’ (ie MCS)

Answer 18

MRI scan

Question 19

describe the causes of the locked in syndrome

Answer 19

Ventral Pontine Damage

Severe Guillain Barre Syndrome

Question 20

describe the locked in syndrome

Answer 20

Conscious (aroused & aware)

Unable to respond (de-efferented)

Most cases are partially locked in:
-preserved vertical eye
movements

-reserved eye opening

Question 21

describe some brainstem reflexes that can be tested for

Answer 21

• corneal-blink reflex

- pupillary light reflex

Question 22

describe brain stem death

Answer 22

Irreversible cessation of brainstem function

Such that consciousness could never be regained

Absent Reflexes:
-Pupils

Ice Calorics

Corneals

Pain

Gag

Cough

Apnoea

-5 min test after pre-oxygenation and allowing CO2 to reach 6Kpa

No arousal

Question 23

what anatomical features correlates with consciousness

Answer 23

Macroscopic Structures:

• Cerebral Cortex
• Reticular activating system
• Thalamus

Microscopic Structures:

• Von Economo Neurones
• Crown of Thorns Neurones

Question 24

describe Von Economo Neurons

Answer 24

Large spindle-shaped soma (or body)

Gradually tapering into a single apical axon

Only a single dendrite facing opposite. F

Question 25

describe the intralaminar thalamic nuclei

Answer 25

• General anaesthetics suppress activity in ILN

Bilateral lesions of C-M nucleus:

• Coma or severe delirium
• Death
• Persistent vegetative state
• Mutism
• Unilateral lesions of C-M nucleus
• –unilateral neglect

Question 26

describe Functional Imaging in Disorders of Consciousness

Answer 26

Coordinate-based meta-analysis

SPECT, PET & fMRI

Decreased activity (compared with healthy controls)

Question 27

describe the anterior cingulate cortex

Answer 27

Role in consciousness?:

-Error detection and conflict monitoring

Sense of voli
tion

Registration of pain

Social evaluation

Reward-based learning

Question 28

describe the Claustrum

Answer 28

Electrode between the left claustrum & anterior-dorsal insula.
Stimulation reproducibly resulted in:
complete arrest of volitional behaviour
unresponsiveness
Amnesia
No negative motor symptoms or mere aphasia.
Disruption of consciousness did not outlast the stimulation
No epileptiform discharges.

Question 29

describe the physiological correlates of consciousness

Answer 29

Surface EEG

• High frequency, de-synchronized waking rhythm
• Alpha rhythm
• Gamma synchronization around 40Hz esp visual cortex
• High band gamma synchrony (85-150hz) – fronto-parietal