T1L14 conciousness Flashcards
definitions of consciousness:
OED
medical (objective) vs philosophical (subjective)
OED- the state of being aware and responsive of ones surrounding (meaning bacteria are conscious)
objective: ability to respond to stimuli
- sensation (pain, touch)
- auditory (verbal and non verbal)
- visual
- olfactory and taste
- the ability to spontaneously move
- the ability to speak
- the ability to orient in time and place (awareness of environment, reason, memory and recognition
subjective: the experience of sensory stimuli
- sensation (pain, interoception, proprioception)
- visual
- auditory
- experience of emotion
- experience of memory
- experience of thought
- experience of self and non self
agency
the experience of free will to:
- act
- speak
- think (imagine, plan, conceive, calculate)
- direct attention
6 physiological and pathological states and conciousness
- sleep
- coma
- death
- PVS
- MCS minimally conscious state
- locked in syndrome
sleep
3 phases
decreased arousal (hence decreased awareness and therefor consciousness)
- physiological
- active process
- reversible and cyclical
slow wave sleep
stage 2 sleep
REM sleep
see s9-11
coma
- complete loss of wakefulness and reactivity
- unresponsive to external stimuli with eyes closed
pathological but usually reversible
causes: - sedation/anaesthesia - epilepsy - disturbance to thermoregulation structural damage: - trauma - tumour - stroke - inflammation - infection
metabolic coma
- hepatic
- uraemia
- diabetic
- pancreatic
- adrenocorticoid failure
outcome:
- reversal or recovery
- vegetative state or minimally conscious state
irreversible cessation of function of:
- brainstem
- cerebral cortex
- body
GCS
3 categories:
- eye opening
- response to verbal motor command
- verbal response
max 15, min 3
s16
vegetative state
- absent awareness (and hence absent consciousness)
- preserved arousal eg sleep/wake cycle
- no voluntary responses
cause: widespread damage to cerebral cortex (anoxia, head injury)- neocortical brain death
persistent vegetative state = more than 4 weeks
permanent vegetative state
= 3 months after non traumatic brain injury
= 1 year after traumatic brain injury
unresponsive wakefulness syndrome- not yet defined
minimally conscious state
like vegetative, but responds more to environment at least one of: consistent movement to command reproducible movement to command object recognition object localization reaching visual pursuit fixation automatic motor response object manipulation localization to noxious stimulation intelligible but non-functional verbalization
awareness has been detected using fMRI
hierarchy of states
coma worse than vegetative worse than MCS
locked in syndrome
conscious - aroused and aware
- unable to respond
- preserved eye movements and some eye opening
causes:
- ventral pontine damage
- guillain barre syndrome
brainstem death
irreversible cessation of brainstem function
absent reflexes:
- pupils
- gag
- cough
- pain
apnoea: tested by preoxygenation, in 5 mins co2 should reach 6kpa
legal requirements to turn off life support
- presence of irreversible cause (anoxia, structural damage)
- absence of reversible cause (drugs, hypothermia, alcohol, poisons, electrolyte disturbance)
- irreversible cessation of:
- brainstem
- cerebral cortex (neocortical death)
- body
repeated after 24 hrs
organ donation
anatomical correlates of conciousness
macroscopic:
- cerebral cortex
- reticular activating system
- thalamus
- default mode network
microscopic:
- crown of thorns neurons
- von economo neurons
von economo neurons
large spindle body, gradually tapers into single apical axon. single dendrite
found in 2 very restricted areas of brain
- anterior cingulate cortex
- fronto-insular cortex
also in wales, macaque monkeys, raccoons
represents convergent evolution due to adaption to larger brains
- allows fast communication across large brains
