1. How does perception depend on sensory processing? Transduction of sensory information The visual system as the “prototype” –Rods and cones and visual acuity –The visual cycle –Visual adaptation –Introduction to colour vision

2. Vision Light wavesLight-sensitive cells in retina Sound waves Pressure-sensitive hair cells in cochlea of inner ear Audition Touch Pain Taste Smell 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 Molecules dissolved in fluid on tongue Chemical-sensitive cells on tongue Molecules dissolved in fluid on mucous membranes in nose Sensitive ends of olfactory neurons in mucous membrane SenseStimulusReceptors

3. Prism white light Gamma Rays X-raysUltra- Violet rays Infrared rays RadarBroadcast bands AC circuits Wavelength in nanometers (billionths of a meter) 10 -5 10 17 10 5

4. Shorter wavelength (or higher frequency): Longer wavelength (or lower frequency):

5. Greater amplitude (brighter colours): Smaller amplitude (duller colours):

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

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

8. Scotopic vision: rods –120,000,000 rods Photopic vision: cones –7,000,000 cones Purkinje “shift” Rhodopsin and 3 kinds of iodopsin Stabilized image

9. Geographical Distribution of Retinal Cells Rods vs. Cones

10. Threshold to light at different wave lengths (Compare with Gleitman, p. 186, where the Y axis is measuring “sensitivity” rather than “energy”) 400 450 500 550 600 650 700 Minimum log energy to generate a response Wavelength in nanometers 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 Cones Rods

11. Dark-adaptation curves 10 9 8 7 6 5 4 3 2 1 0 0 5 10 15 20 25 30 Minutes in the dark Minimum detectable light intensity (log units) Cone adaptation Rod adaptation

12. The nature of color vision: Gleitman pp. 192-196 Trichromatic Theory (at the level of the retina) Opponent-process Theory (further up the system) The Negative Afterimage Phenomenon (Opponent-process theory in action)