Brain & Cognition 2 🧠Flashcards
the perception-action cycle
high level sensory cortex (hierarchical processing) -> meaningful features from the environment. -> motor outputs in reverse hierarchy,
overt orienting and attending
Moving your eyes, body, ears, nose, etc in the direction of a relevant stimulus (what the superior colliculus does).// •Eye & orienting movements
•Colliculus Superior: saccadic eye movements, orienting
•Pulvinar: attention shifts
•Frontal Eye Fields
covert attention
Shifting your attention towards something, without any external, overt signs, i.e. while maintaining fixation. This mechanism has evolved particularly in social animals, in which direction of gaze often has strong meaning (threat, aggression, sexual attraction)// •Pulvinar, FEF •Ventral Frontal cortex •Dorsolateral PreFrontalcortex •Superior Parietal Lobe (SPL) •Temporo-Parietal Junction (TPJ)
cocktail party effect
One may pretend to listen to someone in front of you, while actually focusing on what is said in another conversation.
attentional capture
while listening to the person in front of you, your attention may be suddenly captured by someone saying your name in another conversation:
top down attention
when subjects are instructedto focus their attention on some locationof the visual field (such as in the Posner cueing task). The behavioral effect typically is that reaction times to presented targets are faster at the attended location.10
bottom-up attention
a suddenly appearing stimulus will automatically ‘capture’ attention. Shorter reaction time to primed location. This happens even when subjects know the cue (prime) is mostly invalid (which shows captureis ‘automatic’ and not top down).
inhibition of return
when the temporal interval between prime and target > 300 ms.Now, reaction time is longerfor the cued location. The subject starts to actively suppress attention to the location of the (mostly invalid) cue.
object based attention
Instead of focusing on a particular location, attention can also focus on a particular object/ Attention can be directed towards objects that overlap in space.
feature based attention
shorter reaction times to objects with features
a potential label for assembly coding
Neurons of each assembly fire action potentials in synchrony. Assembly A and B code for different objects. The brain ‘knows’ which parts belong together because those that belong to an assembly fire action potentials in synchronyCross-correlation function reveals synchrony
feature integration theory
Features (like orientation or color) are detected in parallel across the visual field•Yet only at the location where attention is focused, these features are integrated•Can only occur for one or a few items at a time because of capacity limit of attention
crowding
inability to identify objects when surrounded by other objects (in peripheral vision)
biased competition model of attentional selectiong
- High level neurons have large receptive fields
- Multiple stimuli withinthe RF causes the response to be the average of the responses to poor (house) and optimal (face) stimuli that are obtained when these are presented in isolation: face detection (in this case) is hampered by the competing house stimulus
- Attention can biasthe competition, so that the response (here between 150-300ms) is what it would have been when the stimulus was presented alone.
- This resolves the competition, and allows for optimal subsequent processing, detection, reaction etc
things that cause attention
•Increase in fire rate and synchrony of attended locations, features and objects•(therefore) Feature binding and faster responses•A resolving of competition between responses falling with the same receptive field, hence better discrimination, less crowding
change blindness
the inability to notice changes that would be perfectly obvious once attention is directed to them
early vs late selection
1.At what moment during processing?2.At what level of processing in the visual hierarchy (V1, V4, higher?)3.In what pathways does selection occur (dorsal vs ventral)?
inattentional blindness
the inability to memorize and report salient stimuli (such as gorillas) when attention is diverted to some other task-relevant stimulus
early selection
Unattended words are not distinguished from non-words >
attentional blink
the inability to memorize and report a stimulus (T2) that is presented briefly after (up to ~500 ms) a stimulus (T1) that has tobe reported or memorized
late selection
Missed (unseen) T2 houses nevertheless evoke selective activation of the PPA (difference between red and blue). This activation is only amplified (green) when the target is seen
neglect
- No (conscious) percept of contralateral stimuli, that is not caused by a primary sensory deficit (hemianopsia) or a motor deficit (hemiparesis)
- Ignoring of contralateral stimuli•Slower reaction to contralateral stimuli
- Ignoring the ‘contralateral’ half of objects
- Much less eye, head or arm movements (exploration) towards contralateral side
allesthesia
stimuli are perceived at incorrect locations
extinction
- Typically end stage of neglect/ milder versionof neglect
•when both ipsi-and contralateralstimuli are present, only the ipsilateral stimuli are perceived
object based neglect
patients not so much ignore the left side of their visual space, but the left side of objects, regardless of their position in space. Only recognize and copy right sides.
balint syndrome
Very few eye movements: ‘gaze paralysis’. Note how the patient cannot follow the object the doctor is waving in front of her
simultanagnosia
inability to see more than one (part of) object at a time. Note how patient is focused on corner of bed.// inability to understand the spatial relationship between objects, and to see more than one object at a time, not seeing the big picture
unconscious priming
faster categorization of words when preceded by an unseen (extinguished) object of the same category. Yet unable to pick the unseen stimulus
3 guises of consciousness
state, device, sensation
polysomnography
simultaneous recording of EEG (brain) , EMG (muscle tone) and EOG (eye movements)
awake
Low amplitude, high frequency EEG•Saccadic eye movements•Muscle tone (high EMG)
asleep
•High amplitude, low frequency EEG•No saccadic eye movements (drifts)•Low muscle tone (low EMG), paralysis
rem sleep
Low amplitude, high frequency EEG•Saccadic eye movements•Low muscle tone (low EMG), paralysis
sleep paralysis
muscle tone stays flat because of muscle paralysis, yet person awake EEG and EOG like awake
narcolepsy
sudden rem sleep onset
sleep violence
rem sleep without muscle paralysis: violent movements acting out dreams
brain stem reticular system activating system & medial reticular formation
•Set of nuclei in the brain stem•Send fibersto the cortex with modulatory neurotransmitters
reticular activating system
is critical for maintaining the conscious state
brainstem reticular formation
critical for maintaining the conscious state//
projects to the cortex, either directly, or via the intralaminar nuclei of the thalamus
Effects of electrical stimulation of Medial Reticular Formation (MRF) in anesthetized cats
- More high frequency EEG (gamma) relative to low frequency EEG (delta)2.Firing rates variable3.Oscillations go up, more high frequency oscillations4.Synchrony goes up
- cat wakes up
thalamus
gates the info from the senses to the cortex
brain stem mrf
modulates the thalamic gating from arousal to sleep, allows or shuts down the inputs from the senses
utilization behaviour
The tendency to grasp common objects when presented, and perform the function commonly associated with the object.
imitation behaviour/mimicry
The tendency to imitate the gestures, actions, sentences of the person in front of you.
cortical
parietal, temporal, occipital lobe
subcortical
thalamus, basal ganglia, cerebellum, amygdala, hippocampus, brainstem nuclei
frontal
pre-motor, motor cortex
contra-lateral frontal lobe
pre-frontal, pre-motor, motor cortex
how does the pfc enable flexibility of reponses
- Workingmemory, so that longer stimulus response contingencies are possible, delayed responses
- inhibting direct response
- adding value to choice options, and updating these values on the basis of experience
different PFC neurons may encode object identity or location
Different strength of delay activity depending on identity (‘what’) of object (left neuron), Different strength of delay activity depending on location (‘where’) of object (right neuron)
internal value
generalized and automatic VALUE system It assigns value to items we are confronted with, dictates our choices., The PCC (posterior cingulate cortex), Hippocampus, VS (ventralStriatum/ nucleus Accumbens), ventromedialPFC
reward pathway in the brain
vmPFC, signals value for broad range of choices, including moral value, nucleus accumbent, signals value and motivation, dopamine releasing neurons in VTA signal reward or reward prediction
what would be needed for the PFC to perform a function of picking up the phone
reciprocal connections with sensory and motor cortex, neurons encoding rules between input and output, inputs from reward systems (dopamine), rapid learning of such rules, neurons encoding abstract concepts like ‘being at home’ , keeping info ‘on line (WM) because stimulus-response contingencies may span time
choices are determined by
a combination of low-and high-level versions of ‘greed’, ‘fear’, and ‘herd’ behavior•There is not one system that is ‘boss’, or in control. You are the combination of all these ‘drives
readiness potential
The actual movement is preceded by the subjective intent to actwith ~250 ms, But this subjective intent to act is itself precededby ~500 –1000 msof neural activity of the motor cortex (Cz): Our conscious intent to act is in fact the result of an unconscious process. Free will is an illusion
choice blindness
motivations do not lead our choices
post hoc rationalization
Subjects give motivations for ‘their’ choice(which was not their original choice) that vary from confabulation to motivations that pertain to the forced choice instead of the original one
Gazzaniga’s split brain experiments : the brain interpreter
The left hemisphere puts all information together into a final narrative, a story about the motivations and goals of our actions and thoughts
whole body rubber hand illusion
•Subjects (PS) sees himself (VF) in VR goggles•He is stroked on the back in sync with the dummy that is filmed (PF)•After a while, het feels an ‘out of body experience’ towards the VF copy•This does not happen when stroking is out of sync, or with non-corporeal objects
corpus callosum
connects two hemispheres to work together and connects the cortex to the two hemispheres. Connections between homotopicareas, also some between heterotopic areas•Together with Anterior Commisure(not always cut in surgery)•Posterior Commisureconnects subcortical nuclei
the WADA test
each hemisphere is temporarily anesthetized using amobarbital (or sodium amytal, etc).In most people, anesthesia of the left hemisphere results in aphasia, the inability to speak or comprehend languageBut some people have right hemisphere dominance for language, others bilateral language capabilities
split brain patients
The left hemisphere is dominant / necessary for language and speech
Stimuli that are only represented in the right hemisphere cannot be verbally reported
When the posterior part of the callosum is sectioned, higher order, abstract information about the stimulus can be reported, not the stimulus itself (middle panel)
right hemisphere better at
recognizing faces , In order to find this difference, it is required that no ‘verbal’ descriptions of faces can be made (e.g. blonde vs brunette), FFA also more prominent
- sees the big picture (the whole)
left hemisphere
doing semantic categorisation/analysi, seeks patterns and sequences in events
hemianopsia
patients with unilateral lesions to V1. lesions to striate cortex (V1) result in cortical blindness. patients insist they see nothing, have no visual sensation whatsoever, are not aware of anything happening on that side.
blindsight
most likely mediated via the projections of the optic tract to the superior colliculus, which projects to the dorsal stream areas, like MT and parietal cortex.// fairly low visual acuity and lower precision. some have argued that they are mediated by Y type mango cellular LGN pathways conveying only low spatial frequency information. color task present themes challenges to blindsight patients while they are best at localisation, motion and other properties carried by the dorsal pathways
signal detection theory
stimulus A versus B (or absent vs present) generate different internal representations, that are noisy, and distributed as Gaussians. The observer sets an internal criterion. If the signal exceeds the criterion, the observers says A, if it is below, he says B (or Y/N). HIT = saying A when there is A, MISS= saying B when there is A. CR = saying B when B, FA = saying A when B. By manipulating criterion, Hits and FA’s will change. Plotting FA’s vs Hits gives a RecieverOperaterCurve. The d’ is the discriminability of the two stimuli
continuous flash suppression
the stimulus in one eye is strongly masked by a high contrast, colorful, rapidly changing (moving) image in the other eye. This renders the stimulus invisible.
subjective invisibility
report of complete unawareness (1 on Perceptual Awareness Scale) , generally more ‘lenient’. There is often still above chance discrimination on subjectively invisible trials
objective invisibility
chance level performance on YN task: d’ = 0, suffers from the problem ‘what to ask’.
bistable stimuli
Stimulus remains constant, yet conscious percept switches spontaneously
characteristics of binocular rivalry
Presenting two different stimuli to the two eyes (stationary for minutes) results in spontaneous switches of perceiving the one (say left eye) stimulus, then the other (right eye), then the first again, etc. Dominance lasts several seconds, but may vary in length from switch to switch. Dominance length has a characteristic frequency distribution, that is the same in man(green) and monkey
bistable stimulus, rotating random dot sphere
This spontaneously alternates between seeing clockwise (CW) or counter clockwise (CCW) movement. What is seen by the subject can be decoded from motion sensitive and parietal areas involved in 3D perception
global neuronal workspace theory
GNWT distinguishes three modes of processing a stimulus may undergo
- Subliminal, evoking only a weak and not very ‘deep’ activation of cortex
- Preconscious, higher strength and deeper activation, yet because of the absence of attention, it does not reach the ‘Global Workspace’
- Conscious, because attended, signals reach the Global Workspace, and hence can be broadcast to other modules of the brain, enabling ‘access’
attentional blink paradigm
GNWT is supported by paradigms that contrast neural signals for stimuli that are reportedas ‘seen’ versus stimuli that are reported as ‘not seen’.
higher order thought theory
HOTT distinguishes first order(FO) representations from higher order (HO) representationsThe FO representations reside in sensory cortex, memory regions, arousal circuits, reward circuits, proprioception, etc. These FO representations need to be re-represented by higher order regions in frontalcortex. These re-representation are ‘thoughts’ aboutthe FO representation.Many varieties of these ‘thoughts’ and their functions (and many varieties of HOTT)
measuring metacognition
How sure are you that the answer you gave at the detection task is right? The (often speeded) detection / discrimination task is followed by a question where subjects rate their confidenceof the answer. This can be either high /low or 1/2/3/4 etc. Or a post decision wagering (how much do you bet on being right).
integrated information theory
The main tenets of IITcan be presented as a set of phenomenological axioms, ontological postulates, and identities…// integrated information required info being exclusive (differentiated, specialized, selective, specific ) yet also being integrated (the sum being more than the parts)
axioms
self-evident truths about consciousness –the only truths that, with Descartes, cannot be doubted and do not need proof (experience exists, it is irreducible etc.)…
central axioms
intrinsic existence, , information, composition, exclusion
intrinsic existence
each experience is real, and it exist from its own intrinsic perpectic independent of external observers
information
each experience is the particular way it is (composed of a specific set of specific phenomoonenlogical distinctions ) thereby differing from other possible experiences (differentiation)
composition
structured, each experience is composed of phenomenological distinctions, elementary or higher order with exists within it
exclusion
consciousness is definite, in content of spatiotemporal grain, each experience has the set of phenomenal distinctions it has, not less or more, and flows at the speed it does not faster or slower
recurrent processing theory
RPT takes the distinction between feedforwardand recurrent (re-entrant) processing as fundamental to understanding consciousness. It is the neural definitionof consciousness. In doing so, it makes a distinction between attention and consciousness, and between phenomenal and access consciousness.
unconscious inhibition
they had to withold their response when the annulus was preceded by a NO-GO cue (square). The cues were either visible or masked so that they were invisible (chance performance on detection, a). InvisibleNO-GO cues slowed down responses to the annulus (b,c)
orientation
v1, v2, v3, v4
direction of motion
v1, v3, MT, MST
depth
v1, v3, MT
color
v1, v2, v4
more complex shapes
TE(faces), Ent (identities), temporal lobe (houses)
perceptual interference
information/cues that are no longer independent of each other; perceived brightness, perceived color, color constant, many other illusions
perceptual inference
Information that is inferred from the visual input, going beyond what is ‘physically’ there •Illusory contours
•Ambiguous stimuli
•Many other illusions
incremental gestalt grouping
The binding / grouping of distant features and elementsfor which no specific and dedicated systems exist, requiring short or long distance (horizontal) interactions between similar neuronsGestalt rules of perceptual organization
perceptual organiztion
The combination of high and low level features, and from distant locations in the visual field into organized surfaces, objects, scenes
visibility manipulations
Anesthesia Blindsight Masking, Dichoptic masking CFS, Rivalry Objective vs Subjective thresholds
attentional manipulations
Neglect
Attentional Blink
Change Blindness
Inattentional Blindness
functionalist conclusion
Conscious visual experience arises with perceptual organization / binding / grouping / integration
physicalist conclusion
Conscious visual experience arises with the transition from feedforward to recurrent visual processing
attention invokes capacity limit
you can only attend to one or a few items at a time. Yet you seem to seemany more. Somewhere, there is a bottleneck for attention (early or late)
overflow argument
you see more than you can attend, cognitively access, or report
functionalist theories
They associate consciousness with particular functions:
•GNWT: access, attention, working memory, report
•HOTT: higher order thoughts, metacognition
•RPT: perceptual organization, binding
structuralist theories
they associate consciousness with architecture
dualism
mind and body are different entities, different substances, with different rpoperties
interactionism
mental and interact, e.g. via the pineal gland according to Descartes
epiphenomenalism
Physical events cause mental events, but mental events have no effect on physical (brain) events
•E.g. Libetexperiments
monism
Mind and body are the same entities, you can ‘translate’ one into the other
idealism, solipsism
There is only the mental, the physical is a mental imagination (as in the Matrix)
physicalism, materialism
There is only the physical
•View most neuroscientists have
reductive materialism
all mental phenomena can be reduced to physical (e.g. brain) processes
eliminative materialism
Our notion of mental phenomena is flawed, they do not exist
behaviourism
Disregard all the mental, only look at behavior
functionalism
mental phenomena can be realized in different physical structures (brains, computers, aliens), as long as they are analogously related to each other, to the external world, and to behavior
Chalmers easy prol=blems
Still very difficult (maybe requiring decades of science) but we can sort of see the solution lying ahead
ex: •The integration of information by a cognitive system
•The ability of a system to access its own internal states
the hard problem; qualia
The way things look, feel, sound etc.The private, intrinsic, ineffable, and directly apprehensible phenomena of consciousness. For example ‘yellow’ or ‘pain’:
explanatory gap
explaining the function does not explain the experience
philosophical zombies
These are functionally identical to normal humans, except they have no Qualia, no experience.
Mary the super color scientist
She has no color experiences (e.g. she lives in a colorless world), yet knows everything there is to knowabout color processing, rods and cones, the brain etc. Now she leaves her seclusion, and suddenly, for the first time, sees, experiencescolor. Will she not have learned something new? > E.G.
inverted spectrum thought experiment
How can we ever know that what I see and report as red, is in someone else’s mind the same color? Maybe they experience my green, where I experience red. We all call these colors ‘red’, and assigns this color to apples, lights, tomatoes etc, but how do we know we experience the same?
dual aspect theory of information
where info automatically is accompanied by experience (like matter is also energy)
biological chauvinism
is there a missing piece in AI systems that would make them conscious?? does it need to be implemented biologically?
the plant nervous system
Cells of the root apex transmit signals via action potentials. These occur in synchronous bursts, where activity spreads over the root with speeds of ~100 –200 mm/s. Spread of activity depends on Ca+, and Ca+ channels (blocked by Gd3-) Glutamate increases activity, Glu-receptor antagonist DNQX blocked
panpsychism
the idea that everything that processes information (humans, animals, plants, bacteria, robots, thermostats), or even anyhting at all (rocksandair) has some sort of mental ‘life’. Or even is conscious.
p consciousness
raw experience (seeing hearing)
a consciousness
about reflecting on the experience (knowing, reporting, cognition)
granger causality
an analysis of the direction of neural signal flow
premotor theory of attention
attention is just the preparation for an overt shift (eye movement or action)
amodal completion of bilateral stimuli
changes to left hemifield circles (which are in the extinguished visual field) are not detected when indecente (red circle) yet are detected (green circle) when part of an illusory figure (= inner displays)
behaviourally extinction and neglect
seem to cause a deficit in selection at relatively late levels, because we see unconscious recognition of objects, semantic priming, and modaal completion. neural signals on the other hand seem not to survive far beyond V1, suggesting early selection. Still unclear therefor what the level of processing is of neglected stimuli
eeg consists of very selective signals
they are coming from synchronous synaptic currents on the apical dendrites of cortical pyramidal neurons. action potentials or activity from other neurons or from deep structures and nuclei is not visible in the eeg
thalamic gating by the mrf
sensory information (eye, ear) is transferred to sensory cortex PC via thalamic relay cells (th relay). reticular nucleus of the thalamus (ThR/nRt) inhibits this transfer (decrease of sensation). MRF inhibits this inhibition, it causes stronger input from senses to cortex
thalamo cortical oscillations
cortex, thalamus and RNT form a reverberatory circuit that generates different rhythms. slow rhythms prevent sensory inputs from periphery to reach cortex. these slow oscillations are disrupter by MRF stimulation (so that the activity goes back to high freqs and signals can get through)
brain death : somatosensory evoked potential
record response of spinal cord, Brian stem, and cortex to electrical stimulation of the wrist. absence of response beyond p13/n13 is sign of brain death (but make sure noise level is not making N20 invisible). presence of N20 is indicating cortical response and ‘good’ prognosis.
burst suppression EEG
flat EEG interspersed with high voltage bursts of EEG activity
locked in syndrome
trauma or occlusion of basilar artery at the level of the pons, which leaves cranial nerves below nV and the corticospinal and bulbar tracts damaged. : no movements upper face eyes or eyelids. smell, vision hearing and sensations remain present
persistent vegetative state
anoxic or traumatic brain injury. often following coma (if not death) also called unresponsive wakefulness syndrome
inhibition netwrok
ability to rapidly abort planned or already ongoing acctions. right lateralised fronoparietal most porimently the right inferior frontal cortex/gyrus
valuation system
posterior cingulate cortex
hippocampus
ventral striatum/nucleus accumbus
ventromedial PFC
where do valuation systems get the values from?
reward pathway in the brain
ventral tegmental area nucleus accumens (ventral striatum) ventro-medial prefrontal cortex dopaime reward pathway in the brain
reward prediction error hypothesis
via associative learning the reward/dopamine signal can shift from the reward itself to the associated stimulus. the dopamine signal is not about the reward itself, but about the difference between the expected reward and the actual reward
vmPFC ventromedial prefrontal cortex
signals value for broad range of choices, including moral value// allows for more flexibility of responses by adding the possibility to delay responses (WM), inhibit responses or add value to the response options. these values are obtained via associative learning or conditioning. finally, the learned responses are incorporated into lower levels and become ‘routine’
nucleus accumbens (ventral striatum)
signals value and emotion
VTA ventral tegmental area
dopamine releasing neurons as signal reward or reward prediction
inferior temporal cortex
show category selectivity. yet these neurons are overall much less categorical than neurons in PFC
brain regions positively correlated with behaviour change
mPFC and precuneus
spatial summation across midline
faster reaction to two stimuli in blind and intact hemifield than to one stimulus in intact hemifield
metacontrast masking
controls of target and mask overlap.
global ignition
manifests itself typically at a latency of 300-400 ms after stimulus onset
seen vs unseen dichotomy
only N3, P3a, P3b frontal correlates with this. frontal activity is the neural correlate of what subjects report seeing.
attention in recurring processing theory
attention is fully dependent of the feedforward/recurrent dimension. it equals depth of processing. some stimuli may penetrate deeper into the visual hierarchy than others, for ex depending on their relative strength (neural state) or on reactivation hofneurons and pathways (biased state). this selection may influence both feedforward nd recurrent processing
horse race model
cortical activity has to rise to a certain threshold to initiate a saccade. stronger responses reach threshold faster
role of attention
filtering unwanted information so that the attended info can be properly processed and detected or recognised
increase resolution of v4 cells.
attention causes
increase in fire rate and synchrony of attended locations, features and objects
therefore feature binding and faster responses
a resolving of competition between responses falling with the same receptive field, hence better discrimination, less crowding
