Cognitive Neuroscience Lecture 16: Attention 2

L16: Attention 2

What are the units of attention?

-         '''Features: Feature-based attention'''

o Attention to a visual feature (e.g. color, orientation, texture) resulting in enhanced representation of image components related to this feature throughout visual field

o Pop-out: green scarves among red

§ '''Single deviant features are detected quickly'''

o Hard feature search: bald man at a rock concert is hard

o Conjunction search: where’s waldo requires conjunction of several features: spatial frequency (shirt stripes), colors, orientation

o Visual search response time:

§ Pop out search takes same amount of time regardless of sample size

§ Conjunction search takes more and more time as set size increases

o '''Attention capture'''

§ Report the GREEN letter

§ Presented with a green ‘#’

§ '''Distractor in the same ‘Attentional set’ (green) captures attention: contingent capture '''

o Attend to motion vs. attend to color

§ Subjects pay attention to either motion or color depending on instructions

§ Same stim every trial, but only attend to some

§ '''Attending to motion modulates medial temporal regions/V5'''

·       Lateral occipitotemporal regions

§ '''Attending to color modulates ventral area V4 (posterior fusiform gyrus)'''

§ Same result from fMRI and MEG

§ '''Attention modulates activity in feature-specific visual cortex '''

o Effects of feature-based attention

§ '''Attention modulates brain areas involved with processing attended features'''

·       Inflating and flattening a brain: sulci and gyri mapped onto continuous, smooth surface.

·       NOTES

-         '''Objects & Categories'''

o '''Object-based attention: '''can attention be allocated to objects?

§ Cuing spatial attention to a location in space can improve target detection

§ What about spatial attention within objects?

§ Object-based orienting

§ RT shortest for cued valid, longer for invalid same obj, and longest for invalid diff obj

ß controlled for distance from cue and target

§ %signal change difference (i.e. same-object activation) increases as you look at progressively higher visual areas

§ Attention is a higher-level process

o '''Object-based attention deficit: object-based neglect '''

§ Loss of attention/awareness to left side of ‘object’, not necessarily space

§ Spatial neglect: IPL, TPJàexogenous

§ Object based neglect: even more ventral regions (STG)

§ '''Balint’s Syndrome'''

·       Object-based attention deficit

·       Following damage to both parietal lobes

·       Can only see 1 object at a time (simultaneous agnosia)

·       ‘Attentional tunnel vision’

·       Typically temporary

·       Normal visual acuity, depth perception, motion perception, object recognition, etc

·       Balint’s syndrome patient wouldn’t be able to tell if 2 lines were same length or not (since he can only see 1 line at once)

o However, he would know it’s a trapezoid bc all lines connected à one obj

·       Star of David is a star if all same color; if 2 diff colors, it’s 2 triangles

·       Local vs Global: NOTES

o '''Category-based attention'''

§ What we attend to in real life is often more complex than simple features, e.g. people, buildings, cars, etc.

§ Category-based effects

·       When told to attend to motion and…

o …Face movesàFFA more active

o …Place movesàPPA more active

·       '''Category-based attention enhances response of corresponding category-selective visual regions'''

·

·       Fs>F because attention modulates category selective visual regions (same for Sf and S)

§ Some targets of attentional modulation in vision (areas whose activity is modulated by attention): Ventralish

·       STG: early audition

·       hMT+motion

·       V1—V4: early vision

·       Fusiform gyrus & parahippocampal gyrus: faces/houses

§ Some '''sources '''of attentional control: Dorsalish

§

§ Supports dual network theory

-         '''Time: temporal attention'''

o '''Time perception—time’s subjective expansion'''

§ Does attention to an object increase its perceived duration, i.e. expand time?

o '''Oddball expansion''': different types of oddball events tested

§ Time expansion for oddballs

o '''Attentional blink''': what are the two digits?

§ See first but not 2nd because of lag

§ Stage 1: ALL STIM

·       Stim activate conceptual representation (number/letter)

·       Fast, capacity unlimited

·       Conceptual representations fleeting & overwritten rapidly

§ Stage 2: TARGET STIM: bottleneck

·       When target detected, must be protected so that it isn’t overwritten

·       Triggers encoding/consolidation in working memory

·       Slow, severely capacity limited

·       Other representations have to wait (and risk being overwritten)

o You don’t remember the 2nd digit because stage 1 isn’t as effective when you’re busy with stage 2

o Evidence for 2 stages: dissociation in brain 

§ Correct identification of T2, missing T2, or Correct rejection

§ Stage 2: frontal regions respond only to detected (hit) T2

§ Stage 1: ventral temporal regions respond to detected and undetected T2

§

o Change blindness:

§ More likely to notice if they change groups

§ Change depends on what you ‘attend’ to

§ Same social group effect

§ '''If you only encode type/category, you will fail to recognize an exemplar change '''