PowerPoint-Pr

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Sensation Perception
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7 Introduction to V1
-Impromptu session-
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Two parts

• Discussing the midterm

• Introducing V1

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V1
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Multiple terms for the same thing

• V1 in the monkey
• Area 17 in Cats/People (Brodmann Area)
• Striate cortex (Cytoarchitectonically)
• Primary visual cortex (Functionally)

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The early visual system
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LGN Structure
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V1 - Structure
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LGN vs. V1
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LGN receptive fields
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V1 receptive fields
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Classical model of V1 RF genesis
LGN RFs
V1 RF

• V1 RFs are
• Generally larger than LGN RFs
• Elongated, not circular

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Preserved Retinotopy and Cortical Magnification
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Cortical Magnification
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Back to the Core V1 receptive fields
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Function follows Structure
The better a stimulus aligns with the structure
of the receptive field, the higher the firing
rate of the neuron
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ORIENTATION SELECTIVITY
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(Orientation) Tuning curves
Firing rate in Hz
Orientation in degrees
Tuning width in degrees
Watkins Berkley (1974)
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The Function of V1

• Extraction of FEATURES from the Visual image
• Implementing Selfridges Demons
• A hierarchical model

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Selfridges demons
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Another important feature that V1 is selective to

• Spatial frequency (SF)
• Measured in cycles per degree

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SF examples
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Filtered images
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(No Transcript)
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More features next time

• Color
• Direction selectivity (motion)
• Disparity
• Ocular dominance