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

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**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

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Presented with a green ‘#’

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**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

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**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

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**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.

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**NOTES**

**Objects**
& Categories

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

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

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What about spatial attention *within* objects?

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Object-based orienting

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

ß
controlled for distance from cue and target

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%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

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

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Spatial neglect: IPL, TPJàexogenous

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Object based neglect: even more ventral regions
(STG)

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**Balint’s**
Syndrome

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Object-based attention deficit

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Following damage to **both** parietal lobes

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

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‘Attentional tunnel vision’

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Typically temporary

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

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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

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**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.

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Category-based effects

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When told to attend to motion and…

o
…Face movesàFFA
more active

o
…Place movesàPPA
more active

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**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

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STG: early audition

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hMT+motion

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V1—V4: early vision

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Fusiform gyrus & parahippocampal gyrus:
faces/houses

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Some **sources**
**of attentional control: Dorsalish**

§

§
Supports dual network theory

**Time:**
temporal attention

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

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

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

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Time expansion for oddballs

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

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See first but not 2nd because of lag

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Stage 1: ALL STIM

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Stim activate conceptual representation
(number/letter)

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Fast, capacity unlimited

·
Conceptual representations fleeting &
overwritten rapidly

§
Stage 2: TARGET STIM: **bottleneck**

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

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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**

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Correct identification of T2, missing T2, or
Correct rejection

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

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

§

o
Change blindness:

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More likely to notice if they change groups

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Change depends on what you ‘attend’ to

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Same social group effect

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