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CU-Boulder PSYC 2012 - bio psych study guide 3

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II. Study Guide for Exam IIIA. Lecture 14 Sensory Perception and the Visual System1. Be able to list the five different senses and what type of stimuli (light, mechanical forces, chemical signals) they are responsive to.- Sight/Vision – light energy- Taste/Gustation – chemical signals- Smell/Olfaction – chemical signals- Hearing/Audition – mechanical signals (air pressure waves)- Somatosensory – mechanical signals (touch, pressure, pain)2. Describe the three different kinds of sensory receptors and what senses they are associated with.- Photoreceptors – convert light into sense of vison (associated with rods and cones)- Chemoreceptors – convert chemical energy into senses of smell and taste- Mechanoreceptors – convert mechanical energy into senses of hearing and touch3. Describe the factors influencing receptive field sensitivity and give examples of each.- Distance/size, intensity, sharpness/vivid/quality, proximity4. Understand how sensory stimulus intensity and stimulus quality are coded or represented in the nervous system.- Rate of Discharge – sensory stimulus is encoded when a change in the number of action potentials fired by the sensory receptor per unit time- Stimulus Intensity – greater intensity (bright light or loud noise) is encoded by a greater discharge rate- Stimulus Quality – red vs green light can be coded for by the activity of different receptors or by different levels of discharge in the same receptors- Neural Relays – sensory information is conveyed into the CNS through 3-4 neuron relays- Convergence – convergence occurs at each level of relay and receiving input- Decreases acuity (how precisely we can identify where a signal came from)- Increases sensitivity (how likely we are to detect a signal)5. Know the difference in, and be able to define, sensation vs. perception.- Sensation – the registration of physical stimuli from the environment by sensory receptors- Perception – the subjective experience of sensation- Nature of sensation- Context in which the events take place- Emotional state- Past experiences and memories6. Know the difference between the fovea and the blind spot, and specifically how the distribution of rodsand/or cones is different in them.- Fovea – region containing greatest density of photoreceptors (sharpest vision here) and mostly cones are here- Blind Spot – region containing no photoreceptors (where optic nerve exits)7. Be able to compare and contrast rods and cones in terms of their light sensitivity, size/shape, their functions, and what numbers of photopigments they contain.- Cones – responds to bright light, for color vision, sees fine detail, small, 3 kinds of photopigments- Rods – sensitive in dim light, for night vision, many more than cones, large, 1 kind of photopigment8. Know how light is sensed by photopigments—what happens inside photoreceptor cells when light hits them and how does this affect glutamate release? Are photoreceptors hyper-polarized or depolarized by light?- Light hits RHODOPSIN (pigment molecule) -> activates G-Protein -> indirectly closes Na+ channel-> hyperpolarizes cell decreasing release of glutamate9. Be able to list the different neurons involved in the neural relay for the visual system, starting from the photoreceptor and ending in the striate cortex.- Photoreceptors – rods and cones- Bipolar cells – link photoreceptors to retinal ganglion cells- Retinal Ganglion cells – receive inputs from bipolar and amacrine cells (send info to brain)- Horizontal cells – collect info from several photoreceptors (sends to bipolar cells)- Amacrine cells – collect info from bipolar cells (sends to retinal ganglion cells)- Lateral Geniculate Nucleus – get info from retinal ganglion (in thalamus)- Striate Occipital Cortex/ Primary Visual Cortex – roughly processed to identify color, form, and movement (then sent to occipital lobe)10. Be able to compare and contrast rods vs. cones in terms of their convergence on bipolar as well as retinal ganglion cells and be able to explain how this fits with their specific functions.- Rods – large and cylindrical, more sensitive in dim light, one photo pigment- more rods converge on bipolar neurons -> more rod bipolar neurons converge on ganglion cells- Cones – smaller and tapered at the end, responsive to color and bright light, 3 different photo pigments- less convergence happens for detail orientationB. Lecture 15 The Visual System & Visual Processing1. Be able to describe the ventral and the dorsal stream in terms their function and where they send information to.- Ventral Stream – WHAT pathway – object identification processing – send to temporal cortex- Form or Shape- Retinal Ganglion Cell receptive field (photoreceptors -> bipolar cells -> ganglion cell)- On Center Receptivity of Retinal Ganglion Cells- On-Center Cell – increased firing when the light hits the center of the receptive field (like pixels on a computer screen)- Processing Shape in the Inferior Temporal Cortex- Input from the striate visual cortex is send to the inferior temporal cortex through the ventral system (fires most rapidly when striate neurons are active together)- Creates edges and shapes from lines, further into specific shapes- Laterization – words/ gen. objects = Left … faces/ specific objects = Right- KEY POINT! – each cell in the visual striate cortex gets input from many retinal ganglion cells (many ganglion cells -> combine to single LGN cell -> combine to single V1 cell)- Line detection (input from several ganglion “spot cells” to activate single neuron in temporal cortex -> translated to lines and bars instriate cortex -> different neurons respond to slightly different orientations -> arranged into specific columns in the visual cortex)- Color- 3 types of cones (blue, green and red), convergence of information happens in ganglion cells- Color blindness – dichromacy – inability to see specific colors, lack in one type of cone- Motion- Moving objects activate different retinal ganglion receptive fields, detects patterns of movements (like detecting lines), gathers info about object in relation to speed and direction2. Know and be able to describe the 3 different effects of temporal lobe lesions on visual processing.- Visual Form Agnosia – inability to recognize objects from their shape- Achromatopsia – inability to detect ANY colors (still detects information, cannot process)- Akinetopsia – inability to


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