consciousness Flashcards
define consciousness *
the subject experience of the mind, self and world around us
the state of being aware of and responsive to one’s surroundings
that there is something it is like to be in the state of the subjective or 1st person point of view
what is the challenge of consciousness *
the easy problem - how does the brain do behaviour etc from basic machinery
hard problem - why should that feel like anything, the 1st person conscious experience
what are the 3 elements of consciousness *
level - asleep/awake -
content - look awake but content can range from noting to a rich experience, specific awareness of mental states
self - confidence that we are us
describe the content and level of coma *
low both
eyes not open
no awareness
describe the content and level of vegitative state *
level - high - eyes open
low content
describe the content and level of locked in syndrome *
high level and content
just paralysed - motor problem
describle level and content of minimally conscious state eg dementia *
variable and reproducible minimal degree of consciousness
high level
describe level and content of sleep *
level and content gets lower as sleep deeper
REM - level (eyes closed but moving), rish content - dreams
describe how the RAS is involved in consciousness *
regulates vital func
degree of activity is associated with alertness/level of consciousness
reticular formation projects to hypothalamus, thal and cortex
recieves sensory info from ascending tracts (touch and pain), medial vestibular nucleus (vestibular), inferior colliculus (auditory), superior colliculus (vision), medial forebrain bundle (olfactory)
the ventral tegmental area projects dopaminergic neurons to cortex
locus coeruleus projects noradrenergic neurons to cortex
cholinergic neurons project to thalamus - most important for arousal, increase level of activity in cortex via the thalamus
raphe nuclei send serotonergic projections to brain and spinal cord
how is the thalamus involved in consciousness *
cholinergic neurons excite individual thalamic relay nuclei = activation of cortex
cholinergic neurons project to intralaminar nuclei - project to all levels of the cortex
cholinergic neurons project to reticular nucleus - allow other thalamic nuclei info to the cortex
how is the hypothalmus involved in consciousness *
histaminergic tuberomamillary nucleus projects to cortex
involve
d in maintaining awake state
what is the term explaining where consciousness is *
thalamocortical system
what is it abount neurons that control consciousness *
unlikely to be location
number - not that simple - cerebellum has loads, but still conscious w/o it
dynamics of neural activity - way they interact and their action overtime as a collective
what is integration *
unification of brain activity
brain activity overtime is corralated
what is differentiation *
brain activity doing different things - account for the range of things that we experience
what are te 2 types of brain processing involved in consciousness
feed forward - subliminal/non-consciousness
top down recurrent processing - conscious access
what are the brain networks involved in consciousness *
occipital cortex - visual
frontal and parietal - problem solving
default mode network - idea of self, mind wandering, own thoughts - related to the limbic system - posterior cingulate and precuneus important
how can you measure consciousness
use transcranial magnetic stimulation
measure complexity of EEG after TMS - give idea of consciousness
need complexity to have the rich experience
perturbation complexity index - complexity increases wit level of consciousness eg in locked in syndrome similar to being awake
what are te neural correlates of consciousness *
minimal neural mechanisms jointly sufficient for any one specific conscious experience
primarily localised to posterior central hot zone tat includes sensory areas
what is a coma *
absent wakefullness and absent awareness
unarousable unresponsiveness, lasting>6yrs
- cannot be awakened
- no response to pain ligt or sound
- lack normal sleep wake cycle
- does not initiate voluntary actions
what is vegetative state *
wakefulness with absent awareness
preserved capacity for spontaneous or stim induced arousal, sleep wake cycles and reflexive/spontaneous behaviours
complete absence of behavioural evidence for self- or env awareness
what is minimally conscious state *
wakefulness wit minimal awareness
severely altered consciousness
minimal but clear behavioural evidence of self or env awareness is demonstrated
inconsistant but reproducable responses above level of spontaneous or reflexive behavior - indicate some degree of interaction with their surroundings
cause of locked in syndrome
MND
guillain-barre syndrome
what is the area of te brain affected in veg state *
destruction of cortex and hemispheres
intact RAS
area of brain affected in LIS *
in-tact cortex
ascending reticular activating system
damage to ventral pons
area of brain damaged in brain stem death *
irreversible brain stem damage
describe covert awareness in disorders of consciousness *
although no visible sign of consciousness - pt can thonk the correct answer to yes/no qns - still conscious
therefore need to think if we need pain relief or develop a brain-computor interface
describe neglect *
body no longer conscious of other half of body - removed from perception eg cant identify the middle of a line/only draw clock on 1 side
higher order than a visual defect
sensory neglect - prefer the side tey can percieve, lower order sensory cortex fine but loss of perception of reality higher order
describe the interpretation of EEGs *
delta waves <4Hz sleep
theta 4-8Hz
alpa 8-13
B 13-30 normal waking consciousness
gamma - 40
slowing is bad (delta and theta)
alpha normal when eyes closed - especially from posterior electrodes - posterior dominant rhythm - loss of this is bad
used in diagnosis of epilepsy and non convulsive satus (siezures with no convulsions - last for hours or days)
waves slow as go through stages of sleep
what are the points of glasgow coma scale *
picture of scale
localisation of pain - reach and touch where pain is
flexor - arms in
extensor - arms out
what are the metabolic causes of coma *
drug overdose
hypoglycaemia
diabetes - hyperglycaemia
the failures
hypercalcaemia
diffuse intracranial cause of coma *
head injury
meningitis
subarachnoid haemorrhage
encephalitis
epilepsy
hypoxic brain injury
brainstem stroke
hemisphere lesion cause of coma *
cerebral infarct
cerebral haemorrhage - subdural/extradural
abscess
tumour
brainstem cause of haemorrhagic stroke *
infarct
tumour
abscess
cerebellar haemorrage
cerebellar infarct
scan of extradural haemorrhage *
above dura
elliptical
scan of subdural haemorrage *
alongside brain - moon crescent
describe loss of consciousness in extradural haemorrhage *
lose immediately - concussion
lucid interval where fine
lose consciousness again because of rise in intracranial pressure
describe diffuse axonal injury *
head moves eg hemispheres in oppositee dirns - damage to white matter eg corpus collosum
see with gradient echo/suseptibilty weighted imaging - black dots show blood next to the white matter tract
why do posterior brainlesions affect consciousness *
compress the brain stem
why do bilateral medial thalamic infarcts affect consciousness *
mess with thalamocortical system
dexcribe confusion *
mental processes slowed
inattentive or disorientated
difficulty carrying out simple commands or speaking
describe stupor *
only roused by strong sensory stim
describe brain death *
irreversible coma
no brainstem reflexes or response to hypercapnia
eeg not diagnostic
spinal reflexes adn postural movenents might be presnet
effect of lesion to extra-striate cortex *
loss of colour perception
effect of parietal lesions *
lack of awareness in contralateral visual field
is the visual cortex essential for consciousness *
need it to see
but visual cortex can respond to stimuli it doesnt detect
what is essential for consciousness *
feed-forward relay from senses to prefrontal and parietal cortex
and feedback to sensory cortices
content emerges from feedback across brain regions
describe EEG throug sleep *
awake - B wabes
drowsy - A
N1 sleep- theta
N2 - sleep spindles
N3 - delta
REM - fast and random
