Lecture1027

Lecture1027 - 10.4 Structure of the retina. Retinal...

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10.4 Structure of the retina.
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Retinal ganglion cells fall into two types with slightly different receptive field properties: On-center r.g. .c’s Respond to illumination of the center of the receptive field with an increase in a.p. frequency Off-center r.g. .c’s Respond to illumination of the center of the receptive field with an decrease in a.p. frequency
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10.4 Structure of the retina.
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10.14 The responses of on-center and off-center retinal ganglion cells to stimulation. (Part 1)
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Receptive fields of r.g.c’s Illumination of the “surround” the area surrounding the center of the receptive field has the opposite effect to that of illuminating the center On-center r.g.c’s Respond to illumination of the surround of the receptive field with an decrease in a.p. frequency Off-center r.g.c’s Respond to illumination of the surround of the receptive field with an increase in a.p. frequency
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10.14 The responses of on-center and off-center retinal ganglion cells to stimulation. (Part 2) Equivalent to a light annulus (ring) Covering the surround
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10.14 The responses of on-center and off-center retinal ganglion cells to stimulation. (Part 3) Illumination of the surround therefore antagonizes illumination of the center
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10.16 Rate of discharge of an on-center ganglion cell to a spot of light.
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So r.g.c’s have “circular center-surround” receptive fields. Why? – what benefit is this to vision? It means that r.g.c’s are maximally stimulated by edges and lines , where intensity changes rapidly, and NOT by uniform illumination – they are “edge detectors” “Edge detection” is a form of spatial image filtering – allows more “bandwidth” to be allocated to edges and lines during transmission of information along the optic nerve.
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Enhanced edge-detection by retinal ganglion cells Enhanced difference as edge passes Little or no diferemce In response to uniform Light or dark
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Box E The Perception of Light Intensity
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So that’s why center-surround receptive fields exist but HOW are they created? The role of the lateral
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Lecture1027 - 10.4 Structure of the retina. Retinal...

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