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First Hour - How does perception depend on sensory processing?

Sensory Processes. First Hour - How does perception depend on sensory processing?. Transduction of sensory information The visual system as the “prototype” The duplex theory of vision – Rods and cones and visual acuity The visual cycle The stabilized image procedure

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First Hour - How does perception depend on sensory processing?

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  1. Sensory Processes First Hour - How does perception depend on sensory processing? • Transduction of sensory information • The visual system as the “prototype” • The duplex theory of vision • – Rods and cones and visual acuity • The visual cycle • The stabilized image procedure • Dark adaptation • An exploration of the 6th sense – A test for ESP

  2. Light-sensitive cells (rods and cones) in retina Light waves Audition Sound waves Pressure-sensitive hair cells in cochlea of inner ear Touch Pressure on skin Sensitive ends of “touch” neurons in skin Variety of potentially or actually harmful stimuli Sensitive ends of “pain” neurons in skin and other tissue Pain Molecules dissolved in fluid on tongue Chemical-sensitive cells on tongue Taste Smell Molecules dissolved in fluid on mucous membranes in nose Sensitive ends of olfactory neurons in mucous membrane Sense Stimulus Receptors Vision

  3. Duplex Theory of Vision: Two types of receptors • Scotopic vision: rods • Not very accurate • Highly sensitive • Monochromatic vision • 120,000,000 rods • Photopic vision: cones • Responsible for visual acuity • Not as sensitive as rods • Colour vision • 7,000,000 cones

  4. Bipolar cell Ganglion cell Light entering Amacrine cell Horizontal cell Retina (p 185 Gleitman) Photoreceptor layer To brain via optic nerve Rod Cone

  5. 40º 30º 20º 10º fovea light 10º 20º 30º 40º (See Gleitman p. 185) blind spot

  6. Blind spot Fovea Geographical Distribution of Retinal CellsRodsvs.Cones 180000 Rods 160000 Cones 140000 120000 100000 Number of cells / sq. mm. 80000 60000 40000 20000 0 -60 -40 -20 0 20 40 60 periphery Distance from fovea (degrees) (rods) fovea (cones) light blind spot periphery (rods)

  7. By daylight, only the central fovea sees clearly and in colour. On a dark night, only the periphery sees, but only in black and white and with poor resolution. The fovea is “blind.” What the eye sees:

  8. The Visual Cycle • Iodopsin • Rhodopsin • The stabilized image procedure

  9. Cone adaptation Rod adaptation “Rod-cone break” at about 7 minutes Dark-adaptation curves 10 9 8 7 6 5 4 3 2 1 0 More Minimum intensity of light required to see Less 0 5 10 15 20 25 30 Minutes in the dark

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