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ECU PSYC 3312 - Exam 2 Study Guide

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PSYCH 3320 1st Edition Exam # 2 Study Guide Chapter: 3 – 4Chapter 3Be able to define lateral inhibition & what it means. - Lateral inhibition=inhibition that is transmitted across retina & shows how inhibition can cause perceptual effects. It allows us to tell where the edges are. What was the Hartline research involving the Limulus horseshoe crab about & how did it demonstrate lateral inhibition? - They used the Limulus crab b/c its eye made it possible to stimulate neural receptors.- Limulus eye made up of hundreds of tiny structures called ommatidia. Ommatidia has small lenson eye’s surface located over a single receptor.- Hartline recorded from nerve fiber of receptor A found illumination of receptor A caused a large response. - When they added light to receptors in B, the response of the A receptor decreased. - Decrease in the firing of A receptor is caused by lateral inhibition that transmits from B to A across the Limulus’ eye by fibers of lateral plexus. What is the Hermann Grid phenomena? - You have a grid of 9 black boxes on a white piece of paper or on a white background. In betweenthe white spaces, you can see “ghostly” gray boxes at the intersection of the white areas, which decrease or vanish when you look directly at the intersection. Vanishes also if you cover 2 rows of black squares with a white paper. Ghostly gray boxes are not actually there, they’re an illusion. *Be sure you know how to calculate cell’s bipolar outcome for Mach Bands (see the charts we worked on in class! ) What are Mach Bands? (pg. 57 in textbook for picture)- Illusory light & dark bands near a light-dark border. How does lateral inhibition create the Mach Band illusion? - Light moves from receptors A to D (usually left to right) - Each bipolar cell sends inhibition to its neighbors- Can calculate final output of each bipolar cell if you know the output of each receptor & amountof lateral inhibition. *Be sure you know how to do this! Follow the charts from in class examples! What is simultaneous contrast illusion? - When our perception of brightness/color of an area becomes affected by an adjacent/surrounding area. - *The light vs. dark squares examples from the book. Gray squares are actually same color, but we see them as diff. b/c of How is simultaneous contrast created by lateral inhibition? - Receptors stimulated by a pattern like the one in 3.14 in our books.- Receptors under the 2 small squares both receive the same illusion. - Light surrounding the square on left causes receptors under that square to respond rapidly & send large amounts of inhibition to neurons below the center square.- Dark area surrounding the square on the right causes receptors under that square to fire less rapidly, they send less inhibition to neurons under the right square. - Since cells under left square receive more inhibition than the ones on the right, response=decreased more.- Smaller response compared to response of neurons under right square causes the left square toappear much darker. What is White’s Illusion? Why can’t it be explained by lateral inhibition?- Example from in class today (2/4/15) Rectangle/bar grid. Rectangle A that seems to be under the black bars appears much darker than Rectangle B, which is shown on top of the black bars. - Area B receives much more lateral inhibition because more of its border is surrounded by white.Because of this, it’s predicted that B would appear darker than A, but in fact B appears lighter. White’s illusion can’t be explained by lateral inhibition. What are different configurations of receptive fields? - Center-surround organization=area in center of receptive field responds diff. to light than the area in the “surround” of the receptive field. - Excitatory area=a spot of light to the center increases firing- Inhibitory area=stimulation of surround causes a decrease in firing- Excitatory-center, inhibitory-surround receptive field=another term for excitatory center.- Inhibitory-center, excitatory-surround receptive field=receptive field that responds w/inhibition when center is stimulated & excitation when surround is stimulated. *Be sure to know & be able to label the visual pathway from the retina to the cortex (pg. 63). http://academic.udayton.edu/gregelvers/psy323/labels/pathway.asp (I found this link that’s sort of like a game that lets you practice labeling the different pathways! Very helpful!)What is blindsight? - Blindsight=sensory information that surrounds you, like flickers of light, wavelength, movement, & other visual stimuli. People who are blind are able to respond to these types of stimuli that they don’t consciously see. What is the LGN & what is its function? - LGN (lateral geniculate nucleus)=nucleus in the thalamus that receives input fromoptic nerve & communicates w/cortical receiving area for vision. How is an orientation-tuning curve measured? - Determined by measuring responses of simple cortical cells to bars w/diff orientations.- Cell responds w/25 nerve impulses per sec. to a vertically oriented bar & cell’s response decreases as bar is tilted away from the vertical bar & begins stimulating inhibitory area’s of neuron’s receptor fields. - Pg. 65, graph 3.27 D. Graph looks like a general hill graph w/a slope. What is a contrast threshold & how is it measured? - Contrast threshold=minimum intensity diff. btwn 2 adjacent bars that can just be detected. Contrast TH measured by changing intensity diffs btwn light & dark bars until the bars can just barely be seen. Why is the Inferotemporal cortex (IT) important? - IT=area of the brain outside the striate cortex that’s involved in object percep. and facial recognition. What is prosopagnosia? - When people w/temporal lobe damage can’t recognize faces.What is the FFA? - FFA=Fusiform Face Area. Located under temporal lobe. Area is rich in neurons that respond to faces. Chapter 4 What is spatial organization? - Spatial organization= way stimuli at specific locations in environment are represented by activity at specific locations in nervous system. What is a retinotopic map? - Retinotopic map=electronic map of retina on the cortex that show locations on the cortex correspond to locations on retina. - Shows us that 2 points that are close together on an object & on the retina will activate neurons that are close together on the brain. What is cortical


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