exam 3 study - How and What We See What Do We See? What...

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How and What We See What Do We See? What goes in: A 2D pattern of light What we see: A rich world of individual objects that exist and move in 3-Dimensions. Question: How do we create one from the other? Light Enters the Eye Visible light is a small part of an electromagnetic spectrum that includes X-rays and radio-waves. No species can see in the dark (absence of light), but some are capable of seeing when there is little light Light can be thought of as Particles of energy (photons) Waves of electromagnetic radiation Humans see light between 380-760 nanometers Nanometer = 1/billionth of a meter Some important definitions Wavelength – perception of color Intensity – perception of brightness Some important definitions Lens – focuses light on the retina Ciliary muscles alter the shape of the lens as needed Accommodation – the process of adjusting the lens to bring images into focus Eye Position and Binocular Disparity Convergence – eyes must turn slightly inward when objects are close Binocular disparity – difference between the images on the two retinas Both are greater when objects are close – provides brain with a 3-D image and distance information Eye Position and Binocular Disparity The Retina and Translation of Light into Neural Signals Retina - Light sensitive layer located at the back of the eye is “inside-out” Light passes through several cell layers before reaching its receptors The Retina and Translation of Light into Neural Signals Vertical pathway – receptors > bipolar cells > retinal ganglion cells The Retina and Translation of Light into Neural Signals Lateral communication Horizontal cells and Amacrine cells The Retina and Translation of Light into Neural Signals Eye does not transmit a simple representation of the visual world. Organization of the eye allows for a large amount of visual processing to occur long before signals enter the CNS. The Retina Blind spot: no receptors where information (optic nerve) exits the eye The visual system uses information from cells around the blind spot for “completion,” filling in the blind spot Fovea: high acuity area at center of retina Thinning of the ganglion cell layer reduces distortion due to cells between the pupil and the retina Cone and Rod Vision Duplexity theory of vision – cones and rod mediate different kinds of vision Cones – photopic (daytime) vision High-acuity color information in good lighting Concentrated in fovea Rods – scotopic (nighttime) vision High-sensitivity, allowing for low- acuity vision in dim light, but lacks detail and color information Found only outside fovea Cone and Rod Vision (continued) More convergence in rod system, increasing sensitivity while decreasing acuity Only cones are found at the fovea Spectral Sensitivity Lights of the same intensity but different wavelengths may not all look as bright A spectral sensitivity curve shows the relationship between wavelength and brightness There are different spectral sensitivity curves for photopic
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This note was uploaded on 06/10/2008 for the course PSYCH 220 taught by Professor Shervin during the Spring '08 term at Western Washington.

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exam 3 study - How and What We See What Do We See? What...

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