Extrastriate Cortex and Higher Cortical Deficits Adler’s Physiology of the Eye 11th Ed. Chapter 31 - by Boyd & Matsubara

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 Brain New York Times October 10, 2011 Extrastriate Cortex

Monkey Visual Cortex

Retinotopy V1 V2 V3 Multiple “areas” V1, V2, V3 Doctrine of the Receptive Field

Receptive Fields at V1/V2 Border V1 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 - V4 inter-  ori -V4 thick -  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 multimodal Very 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 constancycolor 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 Benton Facial Recognition Test

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 brain inferior 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