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17 Cards in this Set

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  • Back
Where is the area of highest visual acuity on the retina? What is the primary type of photoreceptor cell in this area?
*fovea
*cones
What is the cause of retinitis pigmentosa?
*a mutation in rhodopsin causes misfolding and a new tertiary structure
*the photoreceptor is no longer able to transduce light
What symptoms are seen in retinitis pigmentosa?
*deposits of pigment on retina
*general degeneration of retinal tissue
*disruption of vision, especially in the periphery
How many types of cone cells are there? How are they different?
*3
*based on peak wavelength sensitivity (blue, green, yellow)
What type of photoreceptor provides most of the vision at very low light?
Rods
What happens to the photoreceptor cell when it is hit by light?
It is hyperpolarized and stops releasing neurotransmitter.
What happens to the bipolar cells when light hits the photoreceptor cell?
*this varies by cell
*some bipolar cells are activated by the cessation of neurotransmitter
*some are inhibited
What is the spatial receptive field of an RGC?
The region of the visual field where light can elicit action potential activity from that RGC.
Is the size of the spatial receptive field constant for all RGC's? Why or why not?
*no, it varies by retinal position
*each RGC acquires information from a varying number of photoreceptors
*the more photoreceptors that feed into a single RGC, the larger the spatial receptive field
What is luminance? How can it be quantified?
*the amount of light hitting a surface
*the number of photons
What is contrast? How can it be quantified? What can improve perception of contrast?
*a perceived difference in brightness
*can't be quantified - no absolute fidelity with number of photons
*perceived in a relative context
*addition of color
How do cells in the center vs. the surround of the receptive field differ?
*their response to light - i.e. inhibitory or excitatory for RGC when hit with light
*the color to which they are most sensitive
What type of vision do P cells provide? Describe the size of their receptive fields. What are their responses like?
*form and shape, color and acuity
*small receptive fields
*brisk and sustained responses
What kind of vision do M cells provide? Describe the size of their receptive fields. What kind of responses do they generate?
*perception of movement
*large receptive fields - extensive dendrite array contacts many photoreceptors
*fast and transient responses
What layers of the LGN receive input from the P cells? What are these layers called?
*6,5,4,3
*parvocellular
What layers of the LGN receive input from the M cells? What are these layers called?
*1,2
*magnocellular
The right LGN receives input from the right eye at which layers? Input from the left eye?
*right eye: 5,3,2 (ipsilateral)
*left eye: 6,4,1 (contralateral)