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Convolutions and Correlations. Neurons as Filters. Orientation selective cortical simple cell. Local Circuits in V1:. Retina. stimulus. Selectivity is generated by specific connections. LGN. V1. =. Convolution and cell responses. Image on the retina. horizontal cross section. -. - PowerPoint PPT Presentation
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Convolutions and Correlations
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)()()()()()()( xfxgxgxfduuxgufxh
)()()()()()()( xgxfxfxgduxugufxh
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duuxgufxh )()()(
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Neurons as Filters
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Local Circuits in V1:
Selectivity is generated by specific connections
stimulus
Orientation selectivecortical simple cell
LGN
V1
Retina
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),(),( 2
2
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2
yxGx
yxGy
)cos()()( kxxGxg =
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)()2
)(exp(21)(
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kxtrigxxxg
trig=sin trig=cos
Note:2-dim. Gabor
function are elongated.Thus, cells responses
are orientationselective.Top view: .
trig=cos
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0
),,(),()(),,( tdydxdttyyxxfyxgtvtyxR
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m ore rea lis itic
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duuxgufxh )()()(
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duuxgufxh )()()(
Convolution and cell responsesImage on the retina
horizontal cross section
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-
23Drifting grating stimulus
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A Null-Response is indicative of inhibition
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Detectors are so small close to the fixation point that theirresponses are similar.
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