Extrastriate Cortex and

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Extrastriate Cortex and Higher Cortical Deficits
Adlers Physiology of the Eye 11th Ed. Chapter 31
- by Boyd Matsubara
http//www.mcgill.ca/mvr/resident/
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Multiple Visual Areas Beyond V1
Monkey Brain
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Extrastriate Cortex
Discrete cortical areas
Hierarchical Organization -lower tier, higher
tier
Parallel Streams - what vs. where -
intra-area (blobs vs interblobs) - retinotopy
Feedforward and Feedback connections
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Extrastriate Cortex
Criteria For a Visual Area
Cyto-, myeloarchitecture
Connectivity
New Way to Gain a Clear View of the Brain New
York Times October 10, 2011
Retinotopy
-complete or partial map of visual space
-represent a point in space only once?
-smoothly varying?
-orthogonal axes?
Specialized Function
Topography
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Monkey Visual Cortex
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Doctrine of the Receptive Field
Retinotopy
V2
V3
V1
Multiple areas V1, V2, V3
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Receptive Fields at V1/V2 Border
V2
V1
1
8
16
8
V2
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Functional Division of Labor?
(motion)
(color)
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What versus Where Pathways
Original concept came from lesion studies in
monkeys (Mishkin Ungerleider, 1982)
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What versus Where Pathways
Cross talk remains, and feedback is prevalent
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Extrastriate Visual Areas
thin- ?col - V4
V2
inter-? ori -V4
thick - ?ori ?dis - MT
V3d and V3A
also magno-like
MT - MST
magno input, V1 4B, thick, ?dir, ?dis, motion,
depth
LIP - 7a
Optic flow input, large RF, multimodal, project
to frontal
V4
Central field input V1, V2, ?col ?ori, form
primitives
IT
input V2, V4, object features, face cells,
project to multimodal Very large RF, object
invariance, color constancy, training effects
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MT
Strongly associated with motion perception
Lesion and microstimulation studies in monkeys
(Newsome and Pare, 1988 Salzman, Britten,
Newsome, 1990)
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Wiring Diagram of Visual Areas
Subway Map From Hell
Van Essen et al., 1991
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Human Visual Cortex
MonkeyVisual Cortex
Adlers, 2011
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Human Lesion-Behavioral Correlations
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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
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Retinotopic Areas
Mapping Visual V1 with Clinical Stimulation
(Dobelle et al, 1979)
Mapping Visual Areas Via Callosal Projections
(Clark Miklossy, 1990)
Mapping Visual V1 via Lesion-Scotoma
Correlations (Horton Hoyt, 1991)
state-of the-art update of Gordon HolmesMaps
(1918)
Human V1, V2, V3, V3A, V6, VP, V4, V8
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Syndromes From Isolated Case Studies
Akinetopsia
Human MT
Zihl et al., 1983
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Syndromes From Isolated Case Studies
Achromotopsia
color constancy
color constancy
Human V4/V8
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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)
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Syndromes From Isolated Case Studies
Prosopagnosia
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Syndromes From Isolated Case Studies
Prosopagnosia
Benton Facial Recognition Test
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Neurons Selective For Faces in Monkey IT
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Human Face Areas
anterior

• fMRI studies with humans
• show increased activity in
• the fusiform face area (FFA).

Inverted faces are hard to recognize.
We are all face experts
inflated brain inferior view
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Spatial Neglect
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Artists rendition of spatial neglect
German artist Anton Raderscheidt showed graduated
recovery over eight-month period.
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Drawings of Patients with Spatial Neglect
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Example Lesions that Produce Neglect
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Modern Analysis of Lesion Overlap
Right Hemisphere