Flashcards in Lecture 17 Deck (44):
The peripheral retina is specialized for __, whereas the fovea is specialized for __.
high sensitivity; high resolution
Explain the regional differences in retinal structure and function
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
where is there higher cone density?
ONLY the fovea (center)
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)
in the periphery, convergence of signals from __ increases __; in the fovea, non-convergence of signals from __ increases __
rods; sensitivity; cones; resolution
ratio of photoreceptors to bipolar cells and then to ganglion cells in periphery vs fovea
fovea = 1:1, periphery is more
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
bipolar cells have __ receptive fields
2 classes of bipolar cells (__ and __) based on response to light have different type of __ receptors.
OFF-center and ON-center; glutamate
OFF-center bipolar cells are __, whereas ON-center bipolar cells are __
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?
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
in light, photoreceptors __ and __
hyperpolarize and stop releasing glutamate
what type of glutamate receptors do OFF-center bipolar cells have? what about ON-center bipolar cells?
OFF = Ionotropic channels
ON = mGluR
which is closest to the source of light? photoreceptors, horizontal cells, bipolar cells, amacrine cells, or retinal ganglion cells?
retinal ganglion cells!
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
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
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
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:
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 (__)
left visual field goes through the __ (right/left) optic tract
right visual field info goes through the __ (right/left) optic tract
optic tracts occur __ (before/after) the optic chiasm
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 __
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?
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