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Summary - Class notes - Consciousness & Control
1573513200 Lecture 1: Attention
Wat zegt Victor vaak?What have you?
What is overt orienting & attending?Moving towards a relevant stimulus (Superior Colliculus)
What is Covert Attention?Shifting attention without external signs (Ooghoeken)
What does the dichotic listening experiment show?Can't reproduce the not attended audio stream --> Limited capacity
What does the Posner cuing task show?- Attention --> Faster reation times
- Larger amplitude action potentials
What is cue capture?A cue captures attention even if the cue is mostly invalid
What is inhibition of return in an attentional capture task?Time between prime & Target > 300ms -->
Valid trials longer RT
Invalid trials shorter RT
Attentional capture & Inhibition of return are expressed at the neural level as:- Attentional capture: Increase in sensory responses
- Inhibition of return: Decrease in sensory responses
These have the same spatial distribution as voluntary attention effects.
Object based attention is:Reaction times are faster if a cue is on the same object as the target (even if there is overlap)
What do random dot patterns show in object based attention?Object based attention only occurs when the random dot pattern 'makes' the 2 white bars objects
Feature based attention is:- Attend to a feature of an object (only green objects) makes reaction times quicker
- Enhances responses to that feature all over the visual field
What are some effects of attention?- Increased response times in feature & object based attention
- Biased competition: Better discrimination
- Binding & enhanced neural synchrony
- Faster Responding
- Increases responses in spatial attention (P1, N2pc, Monkey V4)
Research with a house overlapping a face: One of them in motion; What happens when you attend the face or when you attend the house?- Attend to face: Greater activity in FFA
- Attend to house: Greater activity in PPA
What is the difference between feature search & conjuction search?- Feature search: Look for 1 different feature, Pop-out & No search slope
- Conjunction search: More than 1 feature, serial search & non-zero search slope
Why is Conjunction Search slower than feature search?When using Black T's & Red X's --> Find Red T
-Target is defined by shape & color
- Requires binding of features --> Can only be done for one (or a few) at a time & requires top-down attention
What is the feature integration theory?- Features are detected in parallel
- Features are bound into objects by attention (Serial & Attentive)
- The capacity to bind features is limited
What are the labels for Integration theory/ Assembly coding?- Amplitude
- Synchrony: Same object --> Synchrony in neuronal firing
What happens in monkey V4 when a stimulus is attended?Attention increases synchrony between neurons that process attended stimulus.
What is the Horse Race model of attention?- Enhanced sensory activity leads to faster responses because a threshold has to be met to initiate saccade
- Stronger responses (attended responses) reach this threshold faster
What is crowding in attention?Inability to identify objects when surrounded by other objects in peripheral vision.
- Small RF (Fovea): Can resolve the target
- Larger RF (Perihperal): Cannot resolve target --> Crowding
What is a role for attention when alot of information is presented?- Filtering away unwanted information
- Attended information can be properly processed/detected/recognized
When a poor stimulus' contrast is increased, what happens to the firing rate of a V4 cell (when the same preferred stimulus is also in the scene)?Firing rate decreases
What is the Biased Competition Model of attentional selection?- High level neurons have large RF's
- Multiple stimuli in RF --> Response is average for all stimuli (FFA responds less if house & face are present) --> Face detection hampered by the house
- Attention can bias this competition (Attend the face) --> response will be what is would have been if stimulus was presented alone
- Attention resolves the competition: Allows for optimal processing/detection/reaction
Where does simultaneous presentation of stimuli cause competition?- Only in higher visual area's (RF here is large)
- Not in V1: Stimuli not in the same RF (RF's are small here.
How can we measure competition?- Showing stimuli simultaneously or sequentially
- If the response is not the same (adding the sequentials) in the cell --> Competition imulu(Higher visual Area's without attention)
- If response is the same for added sequentials & simultaneous --> No competition (V1) or competition resolved (attention)
What level of visual processing does attention act?V1
When do attention effects arise (in v4)?- As soon as the (visually evoked) response starts
- Preceded by increase in baseline activity
Does attention work the ventral or dorsal stream?- Both
- Ventral stream sensory area's: V4
- Dorsal stream area's: MT
When participants are confronted with a surprise recognition task, unattended words:- Are not remembered (same as fake)
- Are not distinguished from non-words --> Early selection
What is the Attentional Blink?Detection of a first target impairs detection of second target if in close temporal proximity
What happens in the PPA when a house is missed due to attentional blink?- Still evokes some activation (less than seen, more than no house)
What happens to the PPA, when faces are shown and, when houses are shown in the background with or without repetition of the houses in an 1-back task? And in a 2-back task? And if the faces are blurred?- 1-Back task: Respond stronger to new scenes than repeated (Repetition priming) even when faces (foreground) is attended.
- 2-Back task (Working memory load increase): Still selective PPA processing.
- Blurred faces: (Perceptual load increased): No longer processing the scenes
What controls attention? (Coritcal structures & other influences)- Subcortical structures: Superior Colliculus (SC) & Pulvinar (Pv)
- Frontoparietal network
- Outside world: capture
- Electrical stimulation of FEF
What area has executive control of attention and how?- Frontal & Parietal cortex affect perceptual area's through: Cortico-cortico feedback & Recruiting subcortical structures (SC & Pv) to enhance processing in these area's
What does the Superior Colliculus do?- Visual stimulus in RF evokes responce --> This response is enhanced between reciporcal interactions in SC (motor & visual layers)
- This is not the case when eye movement isn't evoked by the stimulus or when the stimulus is covertly attended
Superior Colliculus: Responding to stimuli: Overt attention
What neurons are involved in covert attention?Parietal neurons are involved in saccade generation & covert attention
Where does the Pulvinar Nucleus connect to?Superior Colliculus
Sensory Cortex (Mostly visual)
What is the function of the Pulvinar?Switching attention
What happens when the Pulvinar get inactivated? And when it get stimulated?Inactivation: Less efficient attention shifting.
Stimulation: More rapid disengagement & redirection of attention
What is the role of the Parietal & Frontal cortex in attention?- Mediating shifts of attention
- Mediating overt shift of attention --> Overlap in neural structures involved in overt & covert attention
What is the Premotor Theory of Attention?Attention is the preparation for an overt shift (eye movement or action)
What happens when electrically stimulating the frontal eye fields (FEF)?1. Mimicks covert attention: Lower contrast is needed to detect stimulus change among distractors.
2. Causes V4 cells to respond stronger to stimuli presented in region corresponding to movement field of FEF cells
Both have to have a corresponding movement field of the FEF to the target location or the region in V4
Does capture work when subjects know it's invalid?Yes; Competition between top-down control & bottom-up capture
In the end who is in control of attention?Not one structure.
It's Top-Down (cognitive/complex) vs Capture (direct/stimulus driven)
What lesions cause selective attentional deficits?Occipito-Parietal junction
Inferior Parietal Cortex
- Most often right hemisphere
- No lesions of primary sensory or motor regions
What is Neglect?- No conscious percept of contralateral stimuli (not caused by sensory deficit or motor deficit)
- Ignoring/Slower reaction contralateral stimuli
- Ignoring contralateral half of objects
- Less exploratory movement to contralateral side
- Allesthesia: Stimuli perceived at incorrect locations
What is Hemianopsia?A primary sensory deficit
What is hemiparesis?A motor deficit
What is Allesthesia?Stimuli are perceived at incorrect locations
What is Extinction?- Endstage / milder version of neglect
- Both ipsi & contralateral stimuli present --> Contralateral not seen.
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What are the main findings in split-brain patients?
Can still do much
- Drawing -Selecting, Pointing -Matching objects to words -Other simple semantics -Recognizing family -Recognizing famous people -Emotional responses
What is the difference between partial split brain patients vs complete split brain?
Split: can report that they saw something, but not what, can sort of explain it
Complete: report they saw nothing (still v1 active tho)
What types of activity seems to correlate with NCC
- conscious = stronger activation that can pass a threshold
- synchrony and oscillations
- feedforward vs recurrent processing
What were the basic findings of the dichoptic fusion experiment using textured faces:
similar activation of FFA for both visibleand invisible faces, yet stronger delayed activity,
-more synchronous oscillations,
AND: stronger recurrent interactions between visual areas and FFA for visible vs invisible faces.
conclusion: only as soon as you get recurrent interactions, you have a conscious percept of that face.
What does the dischoptic masking experiment show?
Both oppiste stimulation (different colors) and same stimulation (same colors) reach the ppa, (even tho different is not perceived)
BUT: same stimulation has biggers strength in activating V4 (ffa, ppa)
SO: strength of activation --> conscious NCC?
What does the electrical stimulation experiment from libet show?
It takes 500 ms for consciousness to develop from the start of cortical activation
Implication --> Consciousness plays no role in most of our daily reactions on sensory events (epiphenomenalsim)
Why are these phenomena(Binocular Rivalry(BR), Motion Induced Blindness(MIB), or Rotating Sphere(RS))attractive in the search for NCC?
What does binocular rivalry show
The dominant image gets more strongly processed (NCC?)
This indicates that in this experiment the early visual areas do show modulation between seeing hte one or the other percept.
What are bistable stimuli?
Stimuli that can be interpeted in different ways
when do we consider a piece of the brain part of the NCC, and when not?
When the neural activity correlates with awareness (?)