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 Search  Object pops out  Search time independent of number of distracters

Visual Search

 Serial Search  Less efficient  Search 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 blindness  Difficulty 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 test  Symbol digit modality  Test 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-inattention  Lack of awareness of one side of space  Hemispatial neglect  Similar term  Can include formal tests of neglect

Visual Neglect

 Allesthesia  Tendency 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

 Extinction  Can see an object when one side is stimulated  Will fail to see the same object when both fields are simultaneously stimulated.

 Can be in more than one sensory modality touch

Visual Neglect

 Anosognosia  Lack of awareness of the difficulties  For 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) space  Do not groom left side  Reaching (peri-personal) space  Difficulty locating objects within arms reach  Far (extra-personal) space  Difficult describing distance objects

Tests for Neglect

 Line Bisection  Shift toward side of the lesion  Patient essentially bisecting a shorter line  Shift of visual space (midline shift)

Tests for neglect

 Copy figures  Will miss details on the left side

Tests of Neglect

 Balloon Test

Tests of Neglect

 Behavioral Inattention Test  6 traditional tests  9 behavioral tests  Norm 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