extrastriate cortex and higher cortical deficits adler’s physiology of the eye 11th ed. chapter 31...
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Extrastriate Cortex andHigher Cortical Deficits
Adler’s Physiology of the Eye 11th Ed.Chapter 31 - by Boyd & Matsubara
http://www.mcgill.ca/mvr/resident/
Multiple Visual Areas Beyond V1
Monkey Brain
• Discrete cortical areas
• Hierarchical Organization-lower tier, higher tier
• Parallel Streams- what vs. where- intra-area (blobs vs interblobs)- retinotopy
Extrastriate Cortex
• Feedforward and Feedback connections
• Cyto-, myeloarchitecture
• Connectivity
• Retinotopy
• Specialized Function
• Topography
-smoothly varying?
-orthogonal axes?
-represent a point in space only once?-complete or partial map of visual space
Criteria For a Visual Area
New Way to Gain a Clear View of the BrainNew York Times October 10, 2011
Extrastriate Cortex
Monkey Visual Cortex
Retinotopy
V1
V2
V3
Multiple “areas” V1, V2, V3
Doctrine of the Receptive Field
18
16
9 10 11 12 13 14 15 16
7 6 5 4 3 2 18
Receptive Fields at V1/V2 Border
V1 V2
V2
Functional Division of Labor?
(color)
(motion)
“What” versus “Where” Pathways
Original concept came from lesion studies in monkeys (Mishkin & Ungerleider, 1982)
“What” versus “Where” Pathways
Cross talk remains, and feedback is prevalent
Extrastriate Visual Areas
• MT - MST
• V3d and V3A
• LIP - 7a
• V4
• IT
thin- col - V4inter- ori -V4thick - ori dis - MT
magno input, V1 4B, thick, dir, dis, motion, depth
also magno-like
Optic flow input, large RF, multimodal, project to frontal
Central field input V1, V2, col ori, form primitives
input V2, V4, object features, face cells, project to multimodalVery large RF, object invariance, color constancy, training effects
MT
* Strongly associated with motion perception
Lesion and microstimulation studies in monkeys (Newsome and Pare, 1988; Salzman, Britten, Newsome, 1990)
“Subway Map From Hell”
Wiring Diagram of Visual Areas
Van Essen et al., 1991
Human Visual Cortex
MonkeyVisual Cortex
Adlers, 2011
Human Lesion-Behavioral Correlations
Localization of Function in Humans
Sources of information
• Focal lesions • Histological Analysis• Hemispherectomy• Commissurotomy• Unilateral sodium amytal injection• Brain stimulation• Spontaneous and evoked electrical potentials• Functional brain imaging
• Mapping Visual V1 via Lesion-Scotoma Correlations (Horton & Hoyt, 1991)
• Mapping Visual V1 with Clinical Stimulation
(Dobelle et al, 1979)
• Mapping Visual Areas Via Callosal Projections (Clark & Miklossy, 1990)
Retinotopic Areas
Human V1, V2, V3, V3A, V6, VP, V4, V8
“state-of the-art” update of Gordon Holmes’Maps (1918)
Akinetopsia
Syndromes From Isolated Case Studies
Zihl et al., 1983
Human MT
Achromotopsia
Syndromes From Isolated Case Studies
Human V4/V8
color constancy
color constancy
Visual Agnosia
Aperceptive Agnosia - thought to be due to a disability in the construction of a stable representation of visual form, which impairs all high order recognition.
Associative Agnosia - thought to reflect a deficit in accessing semantic (associative) knowledge about an object following the derivation of an intact perceptual representation of visual form. “Perception somehow striped of its meaning” (Teuber)
Example: The man who mistook his wife for a hat (Oliver Sacks, 1985)
Prosopagnosia
Syndromes From Isolated Case Studies
Prosopagnosia
Syndromes From Isolated Case Studies
BentonFacialRecognitionTest
Neurons Selective For Faces in Monkey IT
Human Face Areas
• fMRI studies with humans
show increased activity in
the fusiform face area (FFA).
anterior
inflated braininferior view
Inverted faces are hard to recognize.
We are all face “experts”
Spatial Neglect
Artist’s rendition of spatial neglect
German artist Anton Raderscheidt showed graduated recovery over eight-month period.
Drawings of Patients with Spatial Neglect
Example Lesions that Produce Neglect
Modern Analysis of Lesion Overlap
Right Hemisphere