Extrastriate cortex: physiology, anatomy, and neuropsychology

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Extrastriate cortexphysiology, anatomy, and
neuropsychology

• Michael Silver
• VS212B
• November 27, 2006

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VS212B syllabus

• Extrastriate cortex
• Visual attention
• Imaging methods in visual neuroscience
• Development / plasticity

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Mound and crater
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Connections
Example connections in monkey visual cortex
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Human visual areas
Left hemisphere posterior view
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Dorsal stream
Ventral stream
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Spiral Motion Aftereffect
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Visual area MT (middle temporal area)
MT
V3a
V3
V2
V1
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Single neuron recording in area MT
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Locating Human MT
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Locating Human MT
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Electrical stimulation in MT
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Motion coherence and MT neurons
Motion stimulus
no coherence
50 coherence
100 coherence
Responses of MT neurons
Preferred direction
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Microstimulation in MT changes motion perception
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What happens if you have damage to MT?
Motion Blindness
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Visual area STS (superior temporal
sulcus)responds to biological motion
STS
MT
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Optic ataxia - posterior parietal cortex damage
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Ventral stream
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Daylight illuminationexamples
Blue sky
Disk of sun
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Photometric invariance
shading
specularity
cast shadow
attached shadow
reflection
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Cortical area V4

• Contains neurons whose responses reflect
  perceived color, not physical wavelength
• Damage to V4 causes cerebral achromatopsia (loss
  of color perception)

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Face perception
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Face perception
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Identity Aftereffects
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pre-adapt
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adapt
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post-adapt
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pre-adapt
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adapt
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post-adapt
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Prosopagnosia (face agnosia)
http//www.choisser.com/faceblind/ http//www.face
blind.org/
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Invariance of object recognition
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Novel examples need to be recognized
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Recognition when only part of an object is
visible
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Recognition from unusual views
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Response selectivity in human inferotemporal
cortex the Jennifer Aniston cell
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the Halle Berry cell
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Columnar architecture in IT
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Columnar architecture in IT
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Faces (FFA) and Places (PPA)
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Parahippocampal place area
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Fusiform face area
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Faces per se or expertise?
Trained subjects to recognize this novel set of
objects
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Face area responses depend on expertise
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Object agnosia

• Can describe features of visual objects
• Can copy drawings of objects
• However, perception of a collection of features
  as an object is impaired

Rose twig
Fencers Mask
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Object agnosia (see only the faces)
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Reading and letter recognition
Aoccdrnig to rscheearch at Cmabrigde Uinervtisy,
it deosn't mttaer in waht oredr the ltteers in a
wrod are. The olny iprmoetnt tihng is taht the
frist and lsat ltteer be at the rghit pclae. The
rset can be a total mses and you can sitll raed
it wouthit porbelm. Tihs is bcuseae the huamn
mnid deos not raed ervey lteter by istlef, but
the wrod as a wlohe. Amzanig huh?
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Misbinding of color and motion
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Summary of dorsal and ventral streams

• Flow of information through dorsal stream from
  early visual cortex to MT and then to parietal
  cortex (driven mainly by magnocellular neurons).
• Dorsal stream specialized for motion processing,
  spatial relationships, and spatial attention.
• Flow of information through ventral stream from
  early visual cortex to V4 and then to
  inferotemporal cortex (driven mainly by
  parvocellular neurons).
• Ventral stream specialized for color and form
  processing and object and face recognition.