Transcript Retinotopy: Background

Vision
Brodmann Original
2
19
Calcarine
18
17
18
19
Collateral Sulcus
37
18
19
18
17
Fusiform Gyrus
Visual System - Medial Structures
5
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
Tootell - Foveal Magnification
12
Retinotopy: Stimulus
Retinotopy:
Results in V1 Slice
Retinotopy: Unfolded results
Response Latency vs. Stimulus Duration
Average of 10 recordings
Stimulus
1 sec
100 ms
17 ms
-5
0
5
10
Data courtesy of Robert Savoy
©2011 Mark Cohen, all rights reserved
www.brainmapping.org
15
sec
18
Contrast
Response
Test
1.6%
6.3%
25%
78%
82%
MT
Cohen
V1
0
60
120
180
240
300
Time (seconds)
Cohen
From R. Tootell
360
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
Dissociation of
Contrast
and Motion
1.6%
6.3%
25%
MT
V1
78% 82%
60
120
180
240
300
360
0
Time (seconds)
From R. Tootell
Cohen 09/28/11
Calculating Images
60
120
Stationary
Moving
Moving
V1
0
Stationary
MT
180
240
Time (seconds)
300
360
• 39/19
Enigma
Isia Levant
Cohen 09/28/11
Calculating Images
Superior Colliculus
Cohen 09/28/11
Calculating Images
Motion After Effect
-24
-12
0
12
24
Time (s)
Culham, et al., J Neurophysiol 81: 388-393, 1999
Cohen 09/28/11
Calculating Images
Area ‘LO’
Rafael Malach
Grill-Spector, et al., Human Brain Mapping 6:316–328(1998)
Cohen 09/28/11
Calculating Images
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
Places
Objects
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
States Task
Washington
Montana
N. Dakota
OregonIdaho
Minnesota
California
Arizona
(with Richard DuBois)
Cohen 09/28/11
Calculating Images
Group Result - Geographic Imagery
BA18 (V2)
L
R
BA 18/19, V1+
BA18 (V2)
BA 19 (+39?) MT
BA 19 (+39?)
MT
z ≤ 2.5
(with Richard DuBois)
Cohen 09/28/11
z≥4
Calculating Images
BA19
UCLA Brain
Mapping Center
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
40
7
39
40
7
39