Lecture 4 - Spatial Vision

Question 1

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How are neurone in the Visual Cortex (V1) organised?

Answer 1

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Neurons in the cortex are organised into layers.
These layers receive different inputs from the LGN (lateral geniculate nucleus).

Question 2

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Define retinotopy.

Answer 2

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Retinotopy: Neighbour relationships in retina are retained in the cortical map

Question 3

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Describe what orientation columns of neurons are.

Answer 3

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See green writing on page 1- end of 2 on G doc notes.

Question 4

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Describe what Sinewave/Sinusoidal Gratings are.

Answer 4

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See purple writing on page 3

Question 5

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make a card here about “visual angle” from lecture

Answer 5

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Question 6

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Read:

Every image can be broken down into sinewave components – Fourier analysis

• If you have enough sinewave gratings that have different orientations, spatial frequencies, contrasts and phases, and you add them up, you will get an image. If you have a sinewave grating, you can make up an image. Basically sinewave gratings are the smallest components (sort of like atoms) for which images are composed. We can very precisely specify and compare different images when we know these components.

Our visual system conducts the equivalent of a local Fourier analysis

Answer 6

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Question 7

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What is a Fourier analysis? Describe it with regards to sinewave gratings.

Answer 7

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Fourier analysis is the study of how general functions can be decomposed into trigonometric or exponential functions with definite frequencies.

See page 5-6 orange/red writing on G doc notes.

Question 8

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Describe how our vision (neurone) can adapt to certain stimuli and therefore alter our vision.

Answer 8

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See page 6-7 green writing on G doc notes.

Question 9

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Possible Essay Questions:

• Using the example of the Tilt Aftereffect, discuss what adaptation can tell us about visual information processing.
• Does the primary visual cortex conduct a Fourier analysis? Discuss.

Answer 9

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Question 10

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Lecture outline:

• Organisation of V1
• Fourier analysis
• Channel model of spatial vision
• Adaptation & after effects

Key Concepts:

• Orientation columns and Hypercolumns
• Spatial frequency & Fourier analysis
• Contrast sensitivity function
• Neuronal channels
• Adaptation & After effects

Answer 10

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