L14: Consciousness Flashcards
define consciousness
The state of being aware of and responsive to one’s surroundings” – OED
name some input and output Requirements of Human Consciousness
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
what are some physiological and pathological states of consciousness
Sleep
Coma
Death
PVS
MCS
Locked in Syndrome
describe the state of sleep
Decreased arousal:
-(and hence awareness & therefore cosiousness)
Physiological
Active process
Reversible & Cyclical
Go over waves that represent:
1-slow wave sleep
2- stage 2 sleep
3- REM sleep
how was it
describe the state of the coma
Characterised by complete loss of wakefulness and reactivity
A state of unresponsiveness to external stimuli with eyes closed
Pathological but usually reversible
Prolonged Unconsciousness
what are the causes of a coma
Causes:
- Sedation / anaesthesia
- Epilepsy
- Electrolyte / metabolic disturbance
- Disturbance of thermoregulation
Structural damage to brainstem / thalamus / cortex
Stroke
Trauma
Tumour
Inflammation
Infection
what are some causes of a metabolic coma
hepatic
uraemia
diabetic
pancreatic
adrenocorticoid failure
what are the 3 outcomes of a coma
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
describe the Glasgow coma scale
slide 16
what is the cause of the vegetative state (“Awake but Unaware”)
widespread damage to cerebral cortex (esp anoxia, head injury) – Neocotical Brain death
describe the vegetative state
Absent awareness (& hence consciousness)
Preserved arousal (preserved sleep/wake cycle)
No voluntary response to environment
Variably preserved reflex responses to environment
what are the 2 categories of the vegetative state
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
describe UWS
Unresponsive wakefulness syndrome’ (UWS)
Proposed by the European Task Force on Disorders of Consciousness
Yet to be fully defined.
describe the minimally conscious state
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
describe emergence from MCS
Emergence from MCS signaled by at least one of 2 items:
- functional communication
- object use.
what do we use the The Coma Recovery Scale - Revised (CRS-R) to distinguish
- distinguish VS/UWS from MCS
how can we Detect for Awareness in
the ‘Vegetative State’ (ie MCS)
MRI scan
describe the causes of the locked in syndrome
Ventral Pontine Damage
Severe Guillain Barre Syndrome
describe the locked in syndrome
Conscious (aroused & aware)
Unable to respond (de-efferented)
Most cases are partially locked in:
-preserved vertical eye
movements
-reserved eye opening
describe some brainstem reflexes that can be tested for
- corneal-blink reflex
- pupillary light reflex
describe brain stem death
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
what anatomical features correlates with consciousness
Macroscopic Structures:
- Cerebral Cortex
- Reticular activating system
- Thalamus
Microscopic Structures:
- Von Economo Neurones
- Crown of Thorns Neurones
describe Von Economo Neurons
Large spindle-shaped soma (or body)
Gradually tapering into a single apical axon
Only a single dendrite facing opposite. F
describe the intralaminar thalamic nuclei
- 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
describe Functional Imaging in Disorders of Consciousness
Coordinate-based meta-analysis
SPECT, PET & fMRI
Decreased activity (compared with healthy controls)
describe the anterior cingulate cortex
Role in consciousness?:
-Error detection and conflict monitoring
Sense of voli
tion
Registration of pain
Social evaluation
Reward-based learning
describe the Claustrum
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.
describe the physiological correlates of consciousness
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
