Vision

2

Brodmann Original

18

18

19

19Calcarin

e

17

Collateral Sulcus

18

1917

37

Fusiform Gyrus

18

5

Visual System - Medial Structures

Visual system

fMRI of the Visual System

• Functional anatomyV1-V4MT and Dorsal StreamLO, IT, & Ventral Stream

• E.g.’s of Functional characterizationContours in V1-> LOOrganization in LO & IT

Retinotopy: Background

11

12

Tootell - Foveal Magnification

Retinotopy: Stimulus

Retinotopy: Results in V1 Slice

Retinotopy: Unfolded results

©2011 Mark Cohen, all rights reserved www.brainmapping.org 18

Response Latency vs. Stimulus DurationAverage of 10 recordings

100 ms

17 ms

1 sec

-5 0 5 10 15

Stimulus

secData courtesy of Robert Savoy

Cohen

Cohen

Contrast Contrast Response TestResponse Test

From R. Tootell

0 60 120 180 240 300 360

Time (seconds)

1.6% 6.3% 25% 78% 82%

MT

V1

Mendola et al.: Approach

• ID areas w/retinotopy and flattening

• Measure response to different kinds of contours

• .Compare patterns of responses across contours and across areas

EG Corbetta et al

Selective attention to shape, color, motion

Attend Shape

Attend Color

Attend Speed

Color19 near 37

• Achromatopsia

• 19/39 MT V5• akinetopsia

Cohen 09/28/11Calculating Images

0 60 120 180 240 300 360Time (seconds)

1.6% 6.3% 25% 78% 82%

MTMT

V1

0 60 120 180 240 300 360Time (seconds)

Mo

vin

g

Sta

tio

na

ry

Mo

vin

g

Sta

tio

na

ry

From R. Tootell

V1

MTMT

Dissociation of Contrastand Motion

Dissociation of Contrastand Motion

• 39/19

Cohen 09/28/11Calculating Images

EnigmaEnigma

Isia Levant

Cohen 09/28/11Calculating Images

Superior ColliculusSuperior Colliculus

Cohen 09/28/11Calculating Images

Motion After EffectMotion After Effect

Time (s)-24 -12 0 12 24

Culham, et al., J Neurophysiol 81: 388-393, 1999

Cohen 09/28/11Calculating Images

Area ‘LO’Area ‘LO’

Grill-Spector, et al., Human Brain Mapping 6:316–328(1998)

Rafael Malach

Object presentation

• Fusiform- 37

Levy et al.: Intro

Background: Subdivisions of ventral cortexLO, FFA, PPA, Chairs, Tools

Q: Is there any organization to this?A: Look at center/periphery retinotopy

Levy et al.: Methods

Stimuli: Faces, houses; center, periphery

Block design, each type alternated with blankBlocks randomly ordered

Correlation analysis

ObjectsObjects

PlacesPlaces

WithincategoryWithincategory

Spatial Frequency and Laterality

Disorders of visual perception

1. Scotoma- loss in retinotopic representation V1-2

2. Achromatopsia V4 lesion

3. Akinetopsia V5 lesion

4. Agnosia

5. Object agnosia

6. Prosopanosia

7. Letter agnosia/pure alexia

8. Anomia vs agnosia?

Agnosia: a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss.

Apperceptive agnosia: -unable to distinguish visual shapes and - have trouble recognizing, copying, or discriminating between different visual stimuli. - unable to copy images

Associative agnosia: -Inability to recognize objects; -retain semantic knowledge; -can describe visual info, can copy

Prosopagnosia:Inability to recognize or discriminate facesFound in RH or bilateral lesionsLateral Fusiform: FFA lesions

Integrative agnosia or Simultanagnosia: can recognize 1 element at a time, cannotProcess more than 1 element or integrate elements into awhole percept (Hooper)

-bilateral P-O junction (blind to objects outside of central focus)-left ventral T-O junction (sequential recognition)

Higher level vision- “what” system

• V2 secondary vision; stereopsis

• V3 form

• V4 color, color/shape

• V5 motion- towards the where; shape from motion

Higher level vision: what vs where

The transition to spatial vision: parietal lobe

Parietal lobe disordersNeglect syndromes: body and spaceWorking memory: sustained “where”

processingApraxic disorders

constructional apraxiasideational (pretend you have a hammer in your hand- show me how you use it)

Sequencing deficits

Cohen 09/28/11Calculating Images

States TaskStates Task

ArizonaArizona

CaliforniaCalifornia

OregonOregon

WashingtonWashington

IdahoIdahoMontanaMontanaN. DakotaN. Dakota

MinnesotaMinnesota

(with Richard DuBois)

Cohen 09/28/11

UCLA BrainMapping CenterCalculating Images

Group Result - Geographic ImageryGroup Result - Geographic ImageryL R

BA 18/19, V1+BA 18/19, V1+

BA19 BA19

BA 19 (+39?) MTBA 19 (+39?) MTBA 19 (+39?)

MTBA 19 (+39?)

MT

BA18 (V2)BA18 (V2)

BA18 (V2)BA18 (V2)

z ≥ 4z ≤ 2.5(with Richard DuBois)

Field cut vs. neglect?

Laterality and visual deficits

• Spatial frequency

• Gestalt vs detail processing

• Tests that emphasize lateralized visual differences– Block design-qualitative analysis

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397

IPS

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397