Vision
2 Brodmann Original
18 19 Calcarine 17
Collateral Sulcus Fusiform Gyrus 18
5 Visual System - Medial Structures
Visual system
fMRI of the Visual System Functional anatomy V1-V4 MT and Dorsal Stream LO, IT, & Ventral Stream E.g.’s of Functional characterization Contours in V1-> LO Organization 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 reservedwww.brainmapping.org 18 Response Latency vs. Stimulus Duration Average of 10 recordings 100 ms 17 ms 1 sec Stimulus sec Data courtesy of Robert Savoy
Cohen Contrast Response Test From R. Tootell 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
Color 19 near 37 Achromatopsia
19/39 MT V5 akinetopsia
Cohen 09/28/11 Calculating Images Time (seconds) 1.6% 6.3% 25%78% 82% MT V Time (seconds) Moving Stationary Moving Stationary From R. Tootell V1 MT Dissociation of Contrast and Motion
39/19
Cohen 09/28/11 Calculating Images Enigma Isia Levant
Cohen 09/28/11 Calculating Images Superior Colliculus
Cohen 09/28/11 Calculating Images Motion After Effect Time (s) Culham, et al., J Neurophysiol 81: , 1999
Cohen 09/28/11 Calculating Images 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 cortex LO, 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 blank Blocks randomly ordered Correlation analysis
Objects Places Within category Within category
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 faces Found in RH or bilateral lesions Lateral Fusiform: FFA lesions Integrative agnosia or Simultanagnosia: can recognize 1 element at a time, cannot Process more than 1 element or integrate elements into a whole 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 disorders Neglect syndromes: body and space Working memory: sustained “ where ” processing Apraxic disorders constructional apraxias ideational (pretend you have a hammer in your hand- show me how you use it) Sequencing deficits
Cohen 09/28/11 Calculating Images States Task Arizona California Oregon Washington Idaho Montana N. Dakota Minnesota (with Richard DuBois)
Cohen 09/28/11 UCLA Brain Mapping Center Calculating Images Group Result - Geographic Imagery LR BA 18/19, V1+ BA19 BA 19 (+39?) MT 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
IPS