Lecture 17 Flashcards by Julia Boudreau

The peripheral retina is specialized for __, whereas the fovea is specialized for __.

high sensitivity; high resolution

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Explain the regional differences in retinal structure and function

(butterfly shape)
VERY densely packed cones in the center (fovea)
cones quickly decrease as rods quickly increase
rods then gradually decrease as cones stay at constant low density

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where is there higher cone density?

ONLY the fovea (center)

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where is there no cones or rods?

where is there no rods?

optic disk (where the optic nerve exits)
very center of the fovea (all cones)

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in the periphery, convergence of signals from __ increases __; in the fovea, non-convergence of signals from __ increases __

rods; sensitivity; cones; resolution

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ratio of photoreceptors to bipolar cells and then to ganglion cells in periphery vs fovea

fovea = 1:1, periphery is more

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in light, absorption of photons leads to __ (__ channels close)
in dark, Vm ~ __, there is high g__, dark current

hyperpolarization of Vm; Na

-35mV; high gNa

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bipolar cells have __ receptive fields

center-surround

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2 classes of bipolar cells (__ and __) based on response to light have different type of __ receptors.

OFF-center and ON-center; glutamate

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OFF-center bipolar cells are __, whereas ON-center bipolar cells are __

hyperpolarizing; depolarizing

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does the cone response to light spot in center look like the response of an ON-center bipolar cell or an OFF-center bipolar cell?

OFF-center

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ON/OFF bipolar and retinal ganglion cells’ response to light vs dark in center… what changes?

they flip. on-center in light spot looks like off-center in dark spot

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in light, photoreceptors __ and __

hyperpolarize and stop releasing glutamate

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what type of glutamate receptors do OFF-center bipolar cells have? what about ON-center bipolar cells?

OFF = Ionotropic channels
ON = mGluR

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which is closest to the source of light? photoreceptors, horizontal cells, bipolar cells, amacrine cells, or retinal ganglion cells?

retinal ganglion cells!

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ON-center bipolar cells have __ metabotropic __

so when transmitter stop being released, the bipolar cells is __ and goes on to __ the ON-center retinal ganglion cell

inhibitory metabotropic GluRs; depolarized; depolarize

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OFF-center bipolar cells have __ ionotropic __, so when transmitter stops being released the cell is __ and __ OFF-center retinal ganglion cell

excitatory ionotropic GluRs; hyperpolarized; hyperpolarizes

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photoreceptors are inhibitory? releasing glutamate in the absence of light and then stopping in light?

in the dark, photoreceptors are __ and __ (do/do not) release glutamate (vice versa for in light)

depolarized; do release glutamate!

photoreceptors are __ when they are activated/ when they see light

hyperpolarized

glutamate excites __ bipolars via __ and inhibits __ bipolars via __

off-center; ionotropic (GluR) receptors; on-center; metabotropic GluR

how did they find out how ganglion cells code patterns of light falling on the retina?

controlled the different patterns of light shown to the eye and recorded response from electrode in an axon in the optic nerve

ganglion cells have __ center-surround receptive fields

2 classes of ganglion cells:

antagonistic

on-center cells and off-center cells

how the firing of retinal ganglion cells in response to light moving across the receptive field

retinal ganglion cells are sensitive to __ levels of illumination

differences in levels of illumination

horizontal cells are responsible for __

antagonistic effects of "surround"

horizontal cells are __, release __

inhibitory; release GABA

in default state (dark), photreceptors in the surround are depolarized and releasing glutamate which __ horizontal cells which __ in light, photoreceptors are hyperpolarized and glutamate release is __ , horizontal cells are __ and stop __

excites; release GABA | decreased; hyperpolarized; releasing GABA

horizontal cells are __ergic and their response is the __ (same as or opposite of) photoreceptors

GABAergic; opposite of

information from the left and right visual fields is received by __; info from the left visual field is received by the __ portion of the right retina and the __ portion of the left retina (nasal or temporal) vice versa for the right visual field..

both left and right retinas; temporal; nasal

__ (nasal/temporal) portions (and the retinal ganglion cells) of each retina cross the optic chiasm (__) __ (nasal/temporal) portions (and the retinal ganglion cells) of each retina do not cross (__)

nasal; contralateral | temporal; ipsilateral

left visual field goes through the __ (right/left) optic tract right visual field info goes through the __ (right/left) optic tract

right; left

optic tracts occur __ (before/after) the optic chiasm

after

retina -> optic nerves -> optic chiasm -> optic tracts -> __ -> __

LGN (lateral geniculate nucleus of the thalamus) | V1 (primary visual cortex)

each LGN has __ layers, each layer having input from __ (one eye or both eyes)

6; one eye

some LGN layers are necessary from perception of __, some for the perception of __

movement; color

going up the LGN layers, they vary by whether or not the eye is

contralateral or ipsilateral

magnocellular layer = __ fast/slow? transient/sustained?__ sensitive, __ insensitive large/small receptive field? can tell you __

large cells; fast; transient; motion sensitive; color-insensitive; large RF; where and how fast

parvocellular layer = fast/slow? transient/sustained? __ sensitive can tell you __

small cells: slow: sustained; color-sensitive; what/object recognition

konicellular layers = lie __ | project to __

in between the main layers | layer 2/3 in V1

left and right eye inputs from retinal project to which layers?

all types

receptive field of LGN neurons are __ (like unlike) retinal ganglion cell receptive fields LGN neurons have a base level of firing without stimulation

V1 is also known as the __ or __

primary visual cortex or striate cortex

LGN axons terminate most heavily in which layer of V1?