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VISUAL PATHWAYS
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Organization of LGN of thalamus
Organization of Visual Cortex
What Stream
How Stream
The Binding Problem
LGN Organization
• Retinotopic maps
• Six Layers
– Three from ipsilateral eye
– Three from contralateral eye
Visual Cortex Organization
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Location columns
Orientation columns
Ocular dominance columns
Hypercolumns
What and How Streams
• What Stream (Ventral Pathway)
– Pattern recognition
– Projects to the temporal lobes
• How Stream (Dorsal Pathway)
– Location and movement
– Projects to the parietal lobes
• Crosstalk between pathways
What Stream
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Input from Parvocellular ganglions
P-cell layers in LGN
Visual Cortex
Inferotemporal Cortex - form
More on the Inferotemporal Cortex
• Some neurons respond best to faces
– Fusiform Face Area
• Damage causes prosopagnosia
• Experience determines what patterns the
neurons respond to
How Stream
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Input from Magnocellular ganglions
M-cell layers in LGN
Visual Cortex
Medial Temporal Cortex (MT) - movement
Parietal Lobes
The Binding Problem
• Information about the same stimulus is
represented in many different brain areas
• How do we combine this information into a
unitary perception?
– Synchronized firing of neurons
– Waves of firing
Sensory Coding
• Sensory Code - pattern of neural responses
that represents perception of the
environment
– Specificity Coding - specialized neurons respond to
particular stimuli
– Distributed Coding - the pattern of response of
many neurons