Visual I
Terms
undefined, object
copy deck
- 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)