Chapter 3 Parallel Processing in the Visual System PDF

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Parallel Processing in Perception in relation to the Visual System...

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Parallel Processing in the Visual System a. Area V1 i. The site on the occipital lobe where axons from the lateral geniculate nucleus first reach the cerebral cortex. ii. This site is (for one neural pathway) the location at which information about the visual world first reaches the brain. iii. Provides a detector for every possible stimulus, making certain that no matter what the input is or where it’s located, some cell will respond to it b. Parallel processing A system in which many steps are going on at the same time. Usually i. contrasted with serial processing ii. An advantage of this is speed 1. Brain areas trying to discern the shape of the incoming stimulus don’t need to wait until the motion analysis or the color analysis is complete 2. Possibility of mutual influence among multiple systems 3. All systems work together rather having priority over the other c. Serial processing i. A system in which only one step happens at a time (and so the steps go on in a series). Usually contrasted with parallel processing d. P cells i. Specialized cells within the optic nerve that provide the input for the parvocellular cells in the lateral geniculate nucleus. ii. Often contrasted with M cell iii. Parvocellular cells 1. Cells in the lateral geniculate nucleus that are specialized for the perception of patterns. 2. Often contrasted with magnocellular cells 3. Spatial analysis and the detailed analysis of form e. M cells i. Specialized cells within the optic nerve that provide the input for the magnocellular cells in the lateral geniculate nucleus. ii. Often contrasted with P cells iii. Magnocellular cells 1. Cells in the lateral geniculate nucleus specialized for the perception of motion and depth. 2. Often contrasted with parvocellular cells 3. Specialize in motion and perception of depth f. What system The system of visual circuits and pathways leading from the visual cortex i. to the temporal lobe and especially involved in object recognition. ii. Often contrasted with the where system. g. Where system The system of visual circuits and pathways leading from the visual cortex i.

to the parietal lobe and especially involved in the spatial localization of objects and in the coordination of movements. ii. Often contrasted with the what system. 2. Putting the pieces back together a. Binding problem i. The problem of reuniting the various elements of a scene, given the fact that these elements are initially dealt with by different systems in the brain ii. the task of reuniting the various elements of a scene, elements that are initially addressed by different systems in different parts of the brain iii. What you perceive is not an unordered catalogue of sensory elements. Instead, you perceive a coherent, integrated perceptual world 3. Visual Maps and Firing Synchrony a. Three elements that contribute to visual system i. Spatial position 1. Part of the brain registering something’s shape is separate from all the parts registering color or motion a. They will keep track of where the target is though ii. The brain also uses rhythm to identify which sensory elements belong with which b. Neural synchrony i. If neurons detecting a vertical line are firing in synchrony with those signaling movement ii. A pattern of firing by neurons in which neurons in one brain area fire at the same time as neurons in another area; the brain seems to use this pattern as an indication that the neurons in different areas are firing in response to the same stimulus. c. Conjunction errors i. An error in perception in which a person correctly perceives what features are present but misperceives how the features are joined, so that (for example) a red circle and a green square might be misperceived as a red square and a green circle. 4. Form Perception a. Necker Cube i. One of the classic ambiguous figures; the figure is a two-dimensional drawing that can be perceived as a cube viewed from above or as a cube viewed from below b.

Figure/Ground organization i. The processing step in which the perceiver determines which aspects of the stimulus belong to the central object (or "figure") and which aspects belong to the background (or "ground").

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Neural Circuits a. The more pressure a cell as, the more it’s going to fire b. The more intense a stimulus, the higher the firing rate...