Lecture 26--visual thalamus & cortex

Lecture 26--visual thalamus & cortex - Ganglion...

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Ganglion cells code contrast • Contrast – the difference in brightness between the center and the surround
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Small receptive field (fine spatial resolution) Tend to be foveal Color coding Large receptive field (poor spatial resolution) Tend to be peripheral Black/white coding
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R+G+B or Receptive fields of P cells Receptive fields of M cells R + G + B R + G + B
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Receptive field size • Receptive field size increases with eccentricity (distance from the fovea) • Receptive field size depends on: – The size of photoreceptors that provide input to the ganglion cell – The number of photoreceptors that provide input to the ganglion cell (convergence)
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Retina Rods – operate under dim illumination; are color blind Cones – operate under bright illumination – Three cone types; mediate color perception Fovea – high resolution area – Contains high density of cones, no rods Ganglion cells provide the output from the retina Ganglion cells use center surround organization to encode stimulus contrast Two receptive field types: On-center off-surround or Off-center on- surround Receptive field size increases with distance from fovea Two types of ganglion cells: M and P
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Lecture 26--visual thalamus & cortex - Ganglion...

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