TB10 P&C Lecture 3; Gain control and normalisation

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  • Created by: mint75
  • Created on: 24-05-16 12:31
What is gain control?
Lets neurons control their sensitivity e.g luminance, contrast, blur
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Why is gain control needed?
Because neurons have a limited range, and range in the word can vary enormously
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What is a canonical computation?
A simple circuit that can explain every brain on the planet
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What is the correct process?
Retina -> LGN -> cortex
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What is contrast?
The luminance variation in the visual field. Expressed as a decimal or percentage
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What is the currency of the early visual system?
Contrast
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Cells in LGN are tuned for...?
Eye of origin
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What was found by Bonds (1989) using masks?
Neurons maintain ability to code differences by shifting sensitivity to the average
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Who proposed 'THE' model?
Heeger
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What is the function of the gain pool?
Feeds back a divisive signal to each neuron receiving an input. inputs divided by SUM of the local average response
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What indicates a PERFECT function in gain control?
The curve shifting to the right
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The gain pool for early contrast normalisation...?
Does not care about spatial frequency or orientation
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According to gain control...?
Neural activity is moderated by the local activity of the group across time and space
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What is a transducer function (Nachmias and Sansbury, 1974)?
How a neuron converts input to output
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What is the 'dipper' function?
Not everything obeys Webers Law. The dip = visual system MOST sensitive to contrast and steepest part of response curve
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In the dipper function...?
Sensitivity is proportional to the slope of the curve and adding a mask shifts the dipper to the right
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Which disorder(s) is sensitive to HZ flicker?
SZ and epilepsy
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Photosensitive epilepsy can be triggered by...?
High contrast visual flicker
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In typical people...?
You get worse at detecting motion as the disk gets bigger bc of long range gain control
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Are older people better or worse at the disc motion task than younger?
Better
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Which gene, if taken from a human and induced in a fruit fly causes Parkinsons?
LRRK2-G2019S
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What % of patients in Tunis carry the 'Parkinson' gene?
40%
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Other cards in this set

Card 2

Front

Why is gain control needed?

Back

Because neurons have a limited range, and range in the word can vary enormously

Card 3

Front

What is a canonical computation?

Back

Preview of the front of card 3

Card 4

Front

What is the correct process?

Back

Preview of the front of card 4

Card 5

Front

What is contrast?

Back

Preview of the front of card 5
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