Study Guide _2

Study Guide _2 - Perception Study Guide#2 Visual Pathways...

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Perception Study Guide #2 Visual Pathways, Receptive Fields & Feature-Detector Approach - what is a receptive field? how is it measured? Area of retina that affects firing rate of any given neutron in the circuit. Can be measured for ANY cell in the visual pathway. Receptive fields are determined by monitoring single cell responses Stimulus is presented to retina and response of cell is measured by an electrode - what would be the difference in the types of response to a stimulus in the receptive field of a cell? Excitation- stimulation of a particular area causes the cell to INCREASE its response rate Inhibition- stimulation of a particular area causes the cell to DECREASE its response rate - as you reach higher levels of the visual system, how are the shapes of receptive fields different? Excitatory-cent-inhibitory surround Inhibitory-center-excitatory surround Output of center-surround receptive fields changes depending on area stimulated: Highest response when only the excitatory area is stimulated Lowest response when only the inhibitory area is stimulated Intermediate responses when both areas are stimulated - know the differences between the “What” system and the “Where” system What- the pathway that reaches the temporal lobes is responsible for determining an object’s identity Where- the pathway that leads to the parietal lobe is responsible for determining an object’s location - know about lateral inhibition Transmitted by the horizontal and amacrine cells Examples: The Hermann Grid-seeing spots at an intersection Mach Bands-seeing borders more sharply Simultaneous Contrast-seeing areas of different brightness due to adjacent area - know about the Ganzfeld and the importance of edges to vision A visual field that contains no abrupt luminance changes and thus no visible contours Color Vision - know the physiology of color vision Trichromatic theory- Proposed in the 1800s Three kinds of cone receptors in a “normal” eye Each cone has a different photopigment, therefore each has a different spectral sensitivity curve Blue Cone (short wavelength receptor) = cyanolabe or “blue catching” (from the Greek) Green Cone (middle wavelength receptor) = chlorolabe or “green catching” Red Cone (long wavelength receptor) = erythrolabe or “red catching” Physiological Evidence: Researchers measured absorption spectra of visual pigments in receptors They found pigments that responded maximally to: Short wavelengths Medium wavelengths Long wavelengths Opponent-Process Theory People seem to respond more to 6 primary colors (red-green, blue-yellow, black-white),
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This note was uploaded on 03/20/2008 for the course CORE 408 taught by Professor Vance during the Spring '08 term at Meredith.

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Study Guide _2 - Perception Study Guide#2 Visual Pathways...

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