Consciousness and the Brain Flashcards
preconscious
accessible but not accessed, it lay dormant amid the vast repository of unconscious states
attention James (1890)
‘the taking possession of the mind, in clear or vivid form, of one out of what seem severalal simultaneously possible objects or trains of thought
conscious access
‘taking possession by the mind’ it is the bringing of info to the forefront of our thinkings such that it becomes a conscious mental objects that we ‘keep in mind’
metacognition
the capacity to think about one’s own mind
binocular rivalry
two incompatible images like a face and a house fight for conscious perception
subliminal
below threshold
supraliminal
above threshold
subcortical circuits
groups of neurons that lie beneath the cortex like amygdala or colliculus that are there to perform dedicated functions such as detection of fearful stimuli enz
blindsight
patients with lesions of the primary visual cortex, main source of visual inputs into the cortex. they can locate where objects are but can not consciously see them
visual form agnosia
for shape recognition
spatial neglect
a lesion to the right hemisphere, (typically in inferior parietal lobe) prevents a patient from attending to the left side of space, as a result he or she often misses the entire left half of a scene or object
subliminal priming
briefly flashing a subliminal word or picture (prime) and immediately followed it with another visible item (the target)
fusiform gyrus
houses advanced mechanisms of shape recognition and implements the early stages of reading // area associated with high level processing of visual objects and visual ares V1 V2 V3 and V4
mcgurk effect
illusion : when seeing a visual person saying “ga” but auditory says “ba” your brain mashes it up to da because it is in conflict
routine bindings
those that are coded by dedicated neurons committed to specific combinations of sensory input
non routine bindings
are those that require the de novo creation of unforeseen combinations, and they may be mediated by a more conscious state of brain synchrony
attentional blink
when two targets T1 and T2 embedded in a rapid stream of events are presented in close temporal proximity the second target is often not seen
refractory period
before a second target enters consciousness, it must wait until the conscious mind is done with the first one
global ignition
whenever we become aware of an unexpected piece of info, the brain suddenly seems to burst into a large scale activity pattern
phase tranistion
a sudden nearly discontinuous change in the state of a physical system// like freezing, consciousness exhibits a threshold, you have to get over this threshold to be consciously seen
recurrent processing theory
the reinfection of information into the same circuit that originated it ‘we could even define consciousness as recurrent processing/// consists both excitatory long-range feedback connections as well as lateral inhibitory connections to integrate and select information// a conscious process corresponds to any neural code that is shaped by recurrent loops from higher order to lower order areas and back
global workspace
an internal system, detached from the outside world, that allows us to freely entertain our private mental images and to spread them across the mind’s vast array of specialised processors
thalamus
involved in attention, vigilance, and synchronization
role : awakening of the entire network, relates to changes in state (with from unconscious to conscious brain)
basal ganglia
crucial for decision making and action (can also be unconsciously activated)
hippocampus
essential for memorising the episodes of our lives and for recalling then
disconnected patterns
encapsulated in our brain stem, the firing patterns that control your breathing are disconnected from the global workspace system in prefrontal and parietal cortex
coma
typically occurs within minutes to hours following damage to the brain, defined clinically as a prolonged loss of the capacity to be roused. no amount of stimulation can awaken him and he shows no signs of awareness of himself or his environment.
many types of problems can cause coma (damage to reticular activating system in the brainstem, damage to cortex)
brain death
distinct state, characterised by a total absence o brain stem reflexes, together with a flat EEG and an inability to initiate breathing. in brain dead patients PET and other measures show that cortical metabolism and the perfusion fo blood to the brain are annihilated. brain death state is irreversible. Cortical and thalamic neurons quickly degenerate
vegetative state
a preserved sleep-wake cycle with no signs of consciousness, a condition that may persist for many years.
locked in syndrome
damage to the brain stem (the pons). condition In which the patient is fully conscious and awake but unable to move or communicate verbally due to complete paralysis of almost all muscles in the body except the eyes. /////
a lesion disconnects the cortex from its output pathways in the spinal cord. it leaves consciousness entirely intact, they cannot be considered as suffering from a disorder of consciousness
mismatch response MMN(mismatch negativity)
as early as 100 milliseconds after the onset of the sound, the auditory cortex is generating a large response to the deviant (it shows as a negative voltage on top of the head). it is an automatic response to the auditory novelty the occurs whether a person is attending, mind-wandering, reading a book watching a movie or even falling asleep or lying in a coma
// the detection of novel auditory stimulus includes 2 distinct neural events : MMN, and later neural response (P300/P3a and P3b)
weighted symbolic mutual information
a program to compute this mathematical quantity, designed to evaluate how much information was being shared between two brain sites
brains conversation was bidirectional
specialised areas of the back of the brain were talking to the generalist areas of the parietal and prefrontal lobes, which returned backward signals
easy problem
re about abilities and functions: we need only nechanisms to explain those. These are problems that we have not solved (perception, memory etc) but in principle we know how to solve even if we have not done yet)
hard problem
why and how do subjective experiences arise from objective brains (neural processes)? “explaining the function doesn’t explain the experience”
dualistic ideas about consciousness
the mind and body are not identical and consciousness cannot be reduced to pure brain activity (video David Chalmers)
materialism
all emergent phenomena, including consciousness, are the result of material properties and interactions in the brain
hemispatial neglect
while drawing neglecting the left side of the drawing
visual form agnosia
unable to identify the shape of objects
dorsal stream
where, acting (unconscious)
ventral stream
what, perceiving (conscious)
color agnosia
usually caused by damage to visual area V4, see the world in black and white
prosopagnosia
face blindness, damage to fusiform area
motion blindness
MT/V5, people cannot perceive smooth motion
neural correlates of consciousness NCC
the minimal set of neuronal events necessary and sufficient for conscious experience
set
lesast number of regions
a necessary condition
for consciousness is a condition that must be satisfied in order for consciousness to arise, for example properly working eyes
sufficient condition
condition that, if satisfied, guarantees consciousness to arise
vigilance
the state of wakefulness, which varies when we fall asleep, wake up, faint, enter a coma or anesthesia
attention
the focus on our mental resources onto a specific piece of information
conscious access
the fact that some of the attended information eventually enters our awareness and becomes reportable to others (in any way)
access of content
‘i was not conscious of the red traffic light’ subliminal, rreconscious, phenomenal, access etc
level of consciousness
(wakefulness or vigilance) the patient was still conscious (coma, vegetative state, sleep, wakefulness, etc)
binocular rivalry
when two distinct images are presented to your two eyes, the brain will spontaneously oscillate and let you see one picture, then the other but never both at the same time
breakthrough time (binocular rivalry )
an image can come up into consciousness suddenly, good for studying sponanteous switches of perception, not optimal for isolating the NCC, because there is no ‘unconscious condition’ to contrast it with
masking (or subliminal representation)
we can flash a word so briefly that study participants will fail to notice it
crowding
creating a carefully cluttered visual scene, wholly invisible to a participant because the other items always win out of the inner competition for conscious perception
attentional manipulations
we van also distract our attention (gorilla experiment)
minimal contrast idea
a pair of experimental situation that are minimally different (physically) but only one of which leads to a conscious experience the other is not
response bias
a behavioural tendency to respond yes which is independent of sensitivity, also reffered to as ‘criterion’
neuroplasticity
the capacity of the nervous system to modify its organisation changes in the structure and function of tehbrain as a result of experience and learning
dichotic listening paradigms
subject with headphones with two stories in each ear and had to attend and repeat what was said in the attended ear
signature
what we measure with brain imaging tools, they reflect the underlying neural mechanism (such as feedback processing ) but are not the mechanisms itself
4 signatures of consciousness (as by dahaene)
- a sudden ignition of parietal and prefrontal circuits 2. a slow wave called the P3 wave (mainly P3b) 3. a late and sudden burst of high-frequency oscillations (gamma >30) 4. a synchronisation of info exchanges across distant brain regions
GNWS theory (global workspace)
- early feedforward processing is (almost) equal
- feedforward activation decays with depth
- crossing of consciousness threshold -> late global ignition by GNW neurons in parietal and frontal cortex “all-or-none process”
- feedback to earlier regions when conscious (thus also all-or-none late processes in earlier regions
which regions are part of the global workspace?
Strong functional and structural long-distance connectivity between different ‘default mode’ areas in prefrontal, parietal, temporal and posterior cingulate cortex (part of global workspace)
more specifically : inferior parietal cortex (IPC), posterior cingulate cortex (PCC) and precuneus, Medial prefrontal cortex (mPFC), , medial temporal lobe (MTL) and anterior cingulate cortex (ACC)
rich hubs phenomenon
when hubs of a network tend to be more densely connected among themselves than nodes of a lower degree
‘identity relationship’
global availability of info (GWS activation) is what we subjectively experience as a conscious state
GNWS
frontal cortexm parietal cortex, cingular cortex, precuneus, temporal cortex (very broad description of the regions involved)
recurrent processing
consists of both excitatory long-range feedback connections (NMDA) as well as literal inhibitory connections (GABA) to integrate and select information.
consciousness requires integration of information via recurrent processing.
agonist
drugs that occupy receptors and activate them // kind mimics the neurotransmitter//inhibition
antagonist
drugs that occupy receptors but do not activate them // blocks the receptor from the neurotransmitter// is an excitatory neuron
excitation
neurotransmitter = gluatamate, receptors : nmda & ampa
inhibition
the capacity of an excited neuron to reduce the activity of its neighbours , neurotransmitter, receptor GABA // response inhibition on no go stimuli is associated with a (mostly right lateralised) frontoparietal ‘inhibition network; van gaal shows it is also the IFC and pre-SMA
global workspace theory : limited conscious experience (Dehaene)
conscious access reflects a selection fo the sensory input (by attention), this suggests that conscious experience is very limited and not rich
sperlings’ attentional cueing paradigm
suggests that you can cue with a tone and they can then report more than initially
information integration theory , 5 axioms
existencem composition, information, integration, exclusion
existence
conscious exists (intrinsically )
composition
consciousness is structured (each experience is composed of many elements)
information
consciousness is differentiated (each experience differentiated form other possible experiences)
integration
consciousness is integrated/unified (each experience is irreducible to components)
exclusion
consciousness is definite, (each experience excludes other experiences)
phi value
integrated information, the quantification of the ‘richness of experience’ in a conscious system : maximal amount of integrated information
anoxic brain injuries
caused by complete lack of oxygen proved to the brain, results in the death of brain cells afteer approximately four minutes of oxygen deprivation (heart attack, drowning)
hypoxic brain injuries
brain injuries due to a restriction of the oxygen supplied to the brain. results in the gradual death and impairment of brain cells
ARAS
ascending reticular activating system, a set of connected nuclei in the brain s that are responsible for regulating wakefulness and sleep-wake transition, damage to this area leads to coma or even death
limited capacity theories of the attentional blink
AB due to over-allocation of limited processing resources to T1 within short term memory.
AB due to T1 occupying limited-capacity stage necessary for consolidation in working memory
//
slagter : the attentional blink is thought to result from suboptimal sharing of limited attentional resources : when many resources are devoted to t1 processing, T2 is more likely to be missed
selection based theories of AB
dysfunctional gating of information into working memory, rather than capacity limitation of working memory per se
EEG
a mixture of oscillations in different frequencies, theta beta and gamma. and you have frequency (how fast), phase (where) and power (how strong)
delta
0-4 Hz
theta
4-8 Hz
alpha
8-13 Hz
beta
13-25
gamma
30 and higher
power
the amplitude of the frequency
we call it feedback when
when information is send from higher order regions are send back to lower order regions (for ex. from prefrontal cortex to visual cortex) // top down activity operates via feedback connections that largely depend on the NMDA pathway
(when top-down attention is absent and bottom-up stimulus strength is weak or interrupted) subliminal (unattended)
very little activation
activation is already weak in early extra striate areas
little or no priming
no reportability
(when top-down attention is present and bottom-up stimulus strength is weak or interrupted ) subliminal (attended)
strong feed-forward activation activation decreases with depth depth of processing depends on attention and task set activation can reach semantic level short-lived priming no durable frontoparietal activity no reportability
(for example, subliminal with and without attention)
(when top down attention is absent and bottom-up stimulus strength is sufficiently strong) preconscious
intense activation, yet confided to sensorimotor processors
occipito-temporal loops and local synchrony
priming at multiple levels
no repeatability while attention is occupied alsewhere (for example in the attentional blink, or inattention blindness)
(when top-down attention is present and the bottom up stimulus strength is sufficiently strong) conscious
orientation of top-down attention amplification of sensorimotor activity intense activation spreading to parietofrontal network long distance loops and global synchrony durable activation, maintained at will conscious reportability
feedforward visual processing
the processing of visual information in the feedforward direction is thought to remain subliminal or at least inaccessible to further cognitive processing
activated global neuronal workspace
once a signal triggers the frontal cortex, a network reverberation is thought to allow visual presentation to be both conscious and available to other cognitive systems /// a conscious process corresponds to information, initially included in one or more specialised processors that enter a large scale reverberant network and is globally accessed by the other specialised processors
the receptive field
of a sensory neuron is a region of space in which the presence of a stimulus will alter the firing of that neuron
GABA
main inhibitory neurotransmitter
NMDA receptor
glutamate main excitatory neurotransmitter
how to reduce consciousness with neurotransmitters
increasing inhibition (GABA agonist) or decreasing excitation (AMPA/NMDA-antagonist) to reduce neural activation
MRS
is a quantitative method to measure the concentration of molecules in a specific region in the brain
difference between consciousness views Dehaene and Lamme
Dehaene : attention gates conscious access (and is thus limited) Lamme : Attention selects from what is already conscious (and is thus rich)
disorder of consciousness
or impaired consciousness, is a state where consciousness has been affected by damage to the brain. consciousness requires both wakefulness and awareness
structural connectivity
strong structural (as well as functional) long-range connectivity between distinct default mode regions in prefrontal parietal temporal and posterior cingulate cortex. “local processing can be complex (houses faces etc) but does not reach our awareness if this happens disconnected from the appropriate higher-level cortical regions (global workspace)
FDG-PET
glucose is labeled with radioactive tracer molecule (injected) this creates a map of glucose uptake in all regions of the brain (metabolic index: global glucose metabolic activity measueed with PET)
phenomenal consciousness
what makes a state phenomenally conscious is that there is something “it is like” to be in that state (the raw experience)
access consciousness
a representation is access conscious if it is broadcasted (global workspace activation) broadly and the information can be used for reasoning and control of action, including reporting
monitoring consciousness
‘metacognitive’ knowledge of one’s own mental states
integrated information theory
a conscious process corresponds to information that is both integrated and differentiated and that cannot be decomposed into causally independent parts
higher order thought theory
neural states of first order networks are viewed as non conscious representations that are rendered conscious when re-presented by the higher order network involving areas of prefrontal cortex //a conscious process corresponds to any first order representation X that enters into a second order, metacognitive representation (“I currently see X”)
subliminal repetition priming
flashing the same word uncosnsciously will minimise the time that the second word (consciously) is named (radio-RADIO), highly sensitive. (anger-ranger won’t work)
repetition suppression/adaptation
neurons recognise when the same stimulus has been presented twice
N400
(400 ms after a word appears) a negative voltage on top of the head, which evaluates hwo much a word fits into a given context. it responds even with words that we do not see (temporal lobe)
bottom up attention
referring to attentional guidance purely by externally driven factors to stimuli that are salient because of their inherent properties relative to the background;
top down attention
, referring to internal guidance of attention based on prior knowledge, willful plans, and current goals.
N2pc
in the parietal lobe reveals an unconscious orientation towards the appropriate side
the aperture problem
refers to the fact that the motion of a one-dimensional spatial structure, such as a bar or edge, cannot be determined unambiguously if it is viewed through a small aperture such that the ends of the stimulus are not visible.
our brain compensates for its slowness by
anticipation, autopilot (like reflexes)
brain web
conscious perception consists of long distance communications and massive exchange of reciprocal signals // the frequency consist of beta band (13-30) or beta band (3-8). slow carriers frequencies are the most convenient for bridging over the significant delays that are involved in transmitting information across distances of several centimeters
difference global and default
not the same but overlap strongly. default : long range connections between distant networks
slagter
ATTENTIONAL BLINK
conclusion : meditation affects the distribution of limited brain resources, smaller attentional blink and reduced brain resource allocation to the first target (smaller T1 elicited P3b). individuals that showed the largest decrease in brain-resource allocation to T1 generally showed the greatest reduction in attentional blink size.
instruments : scalp recorded EEG
van gaal
INHIBITION
fMRI. conscious (weakly masked) and unconscious (strongly masked). unconscious no go signals triggers a substantial slowdown in the speed of responding, as if participants tried to cancel their response but just failed to inhibit it entirely. involved regions are : inferior frontal cortex IFC and pre-supplementary motor area pre-SMA. .
Important study because it shows that the (inhibition control functions in the) PFC can be triggered unconsciously and thereby extend traditional views that tightly link cognitive control to consciousness.
Unconscious inhibitory control can be considered as a relatively “bottom-up” form of cognitive control
van loon
RECOGNITION
Results : ketamine affects top-down processes, in turn influencing activity patterns in early visual cortex (the feedback loop for V1) (the NMDA pathway, antagonist -> so it blocks from NMDA going in).
fMRI multivoxel pattern analysis of object representation in the visual cortex. Use of Mooney images for recognition.
The neural representations of the images are compared in the posterior fusiform pFs.
Ketamine interfered with the Mooney recognition in V1, neural classification performance dropped and the neural representations of the mooney images remained more similar even after having prior experience with the grayscale images. it did not affect pFs
fleming
INTROSPECT
metacognition (anterior prefrontal cortex PFC, Aroc used as quantitative measure metacognitive accuracy) is used to evaluate introspective ability (prefrontal parietal network)
fMRI
Results : Aroc (metacognitive ability, so confidence in the decision) was significantly correlated with grey matter volume in the right anterior PFC and not in how good they were in the task d’, also with white matter in the corpus colosseum
lamme
Clear distinction between attention and awareness.
Visual processing mediated by the feed forward sweep is not accompanied by awareness. recurrent interactions are necessary for visual awareness to arise.
Phenomenal awareness = recurrent processing in groups of neurons (iconic sensory memory)
Access awareness = recurrent interactions that include the prefrontal areas (working memory)
Whether phenomenal awareness goes to access awareness depends on attentional selection mechanisms, via influences on both the feedforwardsweep and recurrent interactions.
monti
fMRI use of tennis (supplementary motor area) and walk around house task (parahippocampal gyrus).
5/54 could wilfully modulate brain activity and was sustained for 30 seconds, 4/5 was VS and all 5 had traumatic brain injury. 1/5 had the ability to apply the technique in order to answer simple yes or no questions accurately
bekinschtein
SOUND ERP and fMRI, VS and MCS, local (within trial) and global (across trials).
Local violation activated the bilateral superior temporal gyro STG and primary auditory cortices.
Global violation : included bilateral doors lateral prefrontal, anterior cingulate, parietal, temporal and even occipital areas thus associated with conscious processing.
3/4 VS patients all local but no global
4/4 MCS patients all local and 3/4 global and recovered to fully conscious state
Out of healthy patients a global effect only was present when subjects were conscious of the global regularity violations.
casali
EEG TMS
Brain response of people who had lost consciousness became either local (suggesting loss of integration) or global but stereotypical (suggesting loss of differentiation)
Dehaene
unseen masked words activate extra striate, fusiform and precentral regions and cause a signifiant reduction in response time and in brain activity to subsequent conscious words, yet fail to elicit the correlated and distributed pattern of activation observed when the same words are consciously perceived.
when visible words were preceded by masked presentation the same words, behavioural responses were significantly accelerated. -> Brian activity was reduced in extra striate fusiform and precentral regions this shows that the repetition suppression phenomenon can be replicated with unseen masked primes.
continuous flash suppression
one eye high contrast other eye face stimulus, you won’t become aware of the face stimulus for a long time. advantage: subliminal info can be presented for a very long time
pattern masking
ccurs when the target and mask locations overlap, won’t see the letter through masking preceded and after
sensitivity
ability of the test to identify those with consciousness, if sensitivity is good the test does not miss any conscious patients
specificity
the ability of the test to identify those patients without consciousness. if specificity is good the test does not ‘miss’ any unconscious patients
contextual modulation
refers to the change in a neuron’s responsivity caused by image structure placed outside of its classical receptive field and to the effect of surround image structure on the perceptual properties of target regions contained within.
pci
perturbational complexity index. calculated by perturbing the cortex with TMS to engage distributed interactions in the brain (integration) and compressing the spatiotemporal pattern of those electrocortical responses to measure the algorithmic complexity (information)
integration of info
recurrent loops via ampa en ndma
bistable perception
things seem to move different ways, binocular rivalry
mvpa
multivariate voxel pattern analysis, looking at pattern of activity
