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

-

+ ++ +

- --

-

-

--

-

-

- -

-

- -

-

+

- -- -

+ ++

+

+

++

+

+

+ +

+

++

+

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