PSY 368 Lecture Notes - Lecture 5: Test Light, Absolute Threshold, Rhodopsin
28 Feb 2019
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Rhodopsin - pigment coating rod outer segments. When a photon of light hits rhodopsin, the retinal and scotopsin binding changes, causing rhodopsin to change its shape (isomerization) This causes receptor sites to open, resulting in cell hyperpolarization. This is the moment of visual sensory transduction (light energy neural energy) In the absence of light, retinal and scotopsin return to their original. Brightness is the perceptual correlate of luminance; luminance is in the world, brightness is in your head. Light (or dark) adaptation refers to a change in brightness sensitivity to accommodate the current level of illumination. Going from bright sun to a dimly lit room will initially leave you nearly blind, but partial vision will return after remaining in the dark for a few minutes (dark adaptation) In a da study, a test light is shown in the periphery, and the subject has to adjust the light intensity until it is just barely perceptible.
