Visual Attention

How much information can we process?

Can we process everything we see? Increase sensitivity to certain stimuli and

decrease sensitivity to others Attention works in space and time

Can we process everything we see? Attention consists of a variety of selection

mechanisms Orientation Selection Sustaining

Visual Search

Attention in space Example Target and distracter

Visual Search

Parallel SearchObject pops outSearch time independent of number of

distracters

Visual Search

Serial SearchLess efficientSearch times depends on the number of

distracters

Attending it time

Rapid serial visual presentation (RSVP) Attentional blink Difficulting in perceiving a second of two

target stimuli.

Do Video Games Improve Attention? Green and Bevalier (2003) nature Compared video game players and non

video game players on spatial and temporal attention tasks.

Attentional blink

Do Video Games Improve Attention? Green and Bevalier (2003) nature Non video game players One group did a shooter game the other

did tetris. 10 1 hour sessions. The shooter group did better on attention

tasks.

How do we perceive change?

http://www.youtube.com/watch?v=Qb-gT6vDrmU

Perception of Scenes or Pictures

Change blindnessDifficulty perceiving subtle changes to a

scene of pictures over time. If the meaning does not change may be hard

to perceive the change.

Measuring visual attention

Tests of visual attention Trail making testSymbol digit modalityTest of Silent Word Reading

Test of Silent Word Reading Fluency Child separates words that run together

Ofgoliketwobig

Of/go/like/two

Disorders of Visual Attention

Visual field deficit Is a measure of attention in space

Visual neglect Difficulty attending to items in one part of space Typically in left field

Visual Neglect

Hemi-inattentionLack of awareness of one side of space

Hemispatial neglectSimilar termCan include formal tests of neglect

Visual Neglect

AllesthesiaTendency to mis-locate stimuli presented on

the affected to the non-affected side.When touched on the left shoulder report

stimulation of the right arm.

Visual Neglect

ExtinctionCan see an object when one side is

stimulatedWill fail to see the same object when both

fields are simultaneously stimulated.Can be in more than one sensory modality-

touch

Visual Neglect

AnosognosiaLack of awareness of the difficultiesFor example, patient is unaware that they had

a stroke and paralysis of the left side.

Examples

http://wn.com/hemispatial_neglect

Visual Neglect

Body (personal) spaceDo not groom left side

Reaching (peri-personal) spaceDifficulty locating objects within arms reach

Far (extra-personal) spaceDifficult describing distance objects

Tests for Neglect

Line BisectionShift toward side of the lesionPatient essentially bisecting a shorter lineShift of visual space (midline shift)

Tests for neglect

Copy figuresWill miss details on the left side

Tests of Neglect

Balloon Test

Tests of Neglect

Behavioral Inattention Test6 traditional tests9 behavioral testsNorm data for neglect patients

Balint Syndrome

Bilateral lesion of the parietal lobes Poor at spatial localization Fixed gaze See one object at a time – Simultagnosia