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Functions of the retina
Retina performs five important jobs:
1. transduction2. wavelength encoding3. light/dark adaptation & chromatic adaptation4. spatial filtering 5. data compression
Pigmented cell
Rod
Cone
Horizontal cellAmacrine cell
Bipolar cell
Ganglion cell
Neural circuitry in the retina
Neural circuits:rod pathway
Rod bipolar
AII amacrines
Neural circuits in the retina(monkey rod pathway)
Parallel pathways (processing streams)
1. Anatomically distinct2. Physiologically/functionally distinct3. Complete coverage4. Recombine
Example: rods and cones
parasol
midget smallbistratified
Some retinal ganglion cell types
Parallel pathways: ganglion cells
Parasol ganglion cell:1. Inputs from many
photoreceptors2. Fast/transient
responses3. Poor spatial resolution4. Combine all cones
(“color blind”)
Midget ganglion cell:1. Inputs from few (or
one) photoreceptors2. Slow/sustained
responses3. High spatial resolution
Field et al., Nature (2010)
Ganglion cell receptive fields & inputs from cone lattice
Field et al., Nature (2010)
Ganglion cell mosaics
Retinal ganglion cell responses
stimulus: on off stimulus: on off
on-center RGC off-center RGC
Retinal ganglion cell measurements(Kuffler 1950s)
Receptive fields: center-surround organization
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On-center, Off-surround Off-center, On-surround
Receptive Fields
Center-surround circuitry in the retina
On-off layer segregation
Linearity of RGC responses
Linearity of RGC responses
+--
Ganglion cell
Bipolarcells
Photoreceptors
Linear receptive field model
Linear receptive field model
Neural image
Input image(cornea)
“Neural image”(retinal ganglion cells)
Center-surround receptive fields: emphasize edges.
Neural image
‘On’ and “off” responses
Stimulusx
t
Receptive field
Functions of the retina
Retina performs five important jobs:
1. transduction2. wavelength encoding3. light/dark adaptation & chromatic adaptation4. spatial filtering 5. data compression
Simulations of the high spatial resolution in central vision coupled with the blurry low spatial resolution in the periphery.
Retinal inhomogeneity
Distribution of rods and cones
Foveal cone mosaic
rods
cones
Near periphery photoreceptor mosaic
Smallbistratified
Parasol
MidgetDen
drit
ic f
ield
dia
met
er (m
icro
ns)
Retinal eccentricity (mm)
Dendritic fields increase with eccentricity
(Dacey, 1993; human)
Diseases of the retina
macular degeneration
retinitis pigmentosa
Retinal implants