On the perturbational complexity index
Introduction
Objective measure
Sensitivity to consciousness
consciousness meter
Discussion
Advantage: quantification on a continuum
quantification of consciousness
Disadvantages: Variability between stimulation sites?
first steps, inspirtions, massemmini
Methods
EEG vs hdEEG
TMS
Algorithmic Compression
Oweb Monti, command following, purposeful behavioutr
Availability
Sensitivity
Cost
integrity of the neuromuscular system
integration
differentiation
differences in what is exactly measured
algorithmic complexity
Further Research
Results
sleep
Psychedelic state?
posterior hotzone
aneasthisia
disorders of consciousness + locked in syndrome
bridging principles
large scale response dynamics
vs alternatives: brain metabolism, cerebral perfusion
set of altered states of consciousness
input-output relationships
uws, minimally conscious state
sensory stimulation: resting vs stim no diff -
adaptation
automatic processing vs conscious perception
risk of a purely stimulation based procedure
attention praradigms stronger, vs just passive stim, better to involve sub in task, boost cognitive
detecting vs communicating
ethical considerations
pain medication in minimally conscious states
neural sign - sign for command following - cognitive task
fully disconnected, input-output disconnection
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low sensitivities for this techniques
low sensitivites
cognitive task:
detached from input output
even verbally recovered: memor y, concentration, attention, motivation
bypassing
requires input - understand process sensory information
consciousness can be generated from within
lack of options, prevent brain death, what does it feel like
artifacts of modern medicine
correlational measure
theoretical foundation (grounded) + practical use
indepndent of sensory processing and motor behaviour
neural correlates and neural substrates
activity as high as in wakefullness
recovery of brain ativity not necessarily needed (also brain metabolsim)
dissociation: decrease in activity during seizures, not based on activity, or metabilic rate
synchrony dissocation - seizures
spectral features, entropy : paradoxes
do not work in all cases
not necisarrily on scalp
contrast with empirical findings
sensitivity and specificity
too many exceptions
IIT
start from phenomenology, then go to the brain
balance btw unity and diversity
modular vs full connection
optimization - functional differnetiation and integration
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so far dimensions have not been combined , phase
difference: coherence - observing vs perturbing
global vs stereotypical - capture
causal interactions vs temporal correlation
intrinsically integrated information
knock on cortex, record the echo
approximates cortico-cortical interactions/potentials
escape the input output chain
source modelling
determinsitic activity
central gravity still there
propofol midazolam ketamine
ketamine - hallucinations - model of full disconnection and conscousness
xenon
stimulate left over cortex islands with neuronavigation
response in VS - sleep like (provided no complete death of neurons)
adavantage: sensitivity to minimally conscious state
therapeutic potential - building up capapcity
determinisitc patterns, binarize
different things at different times
joint presence as an important criterium
circularity: no independent evidence to subjective reports
calibration of measure
benchmark to derive a cutoff
no report, immediate report, delayed report
benchmark population
roc analysis
sensitivity and specificity 100%
detection rates - brain derived fmri active paradigm - 3, p300 erp - 30% - eeg - söow wave alpha delta - 60%, PCI - only 2 out of 38 missed - sensitivity - 94,7 % - perturbing is mroe than observing
retained capacity that has been missed by focusing on overt
input-output behaviour
aphalic syndrome
appalic syndrome
assume there is a physical substrate that is cabable of consciousness until proven otherwise
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resore functional external communication or restore complexity
cut-off values, benchmark poulation validation
Mechanims
why does complexity collapse
nobody is cutting the snapses - physiological state no one is cutting the synapses
functional change in how neurons are working
neuronal bistability
anatomical structure is the same
stochstical continuation of activity
causal trace
corroborated by intracranial data
complexitiy recovery, local physiological mechnaisms, low complexity state - pharmacological interventions
cortical deafferentiation
different perturbations = different reposnes
coarse measurement, only a flavour of phi
relative changes not absolute
across subjects as well as within subjects
calibration - exhaustive measure, rel measure
content vs complexity
system property
confounding factors in ROC curves - forgot to have been cosncious - ground truth that you trust - best: own experience, subjective reports
make up and confabulate
step wise distillation
local global - bekenschtein - distraction