1 / 18

Retinal Circuit and Processing March 23, 2007 Mu-ming Poo

Retinal Circuit and Processing March 23, 2007 Mu-ming Poo. Overview of the retinal circuit Receptive field (RF) of retinal ganglion cells (RGC) Neural circuitry underlying the RGC receptive field. Lens defects:

rmontero
Download Presentation

Retinal Circuit and Processing March 23, 2007 Mu-ming Poo

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Retinal Circuit and ProcessingMarch 23, 2007 Mu-ming Poo • Overview of the retinal circuit • Receptive field (RF) of retinal ganglion cells (RGC) • Neural circuitry underlying the RGC receptive field

  2. Lens defects: Myopia (nearsightedness) – focusing in front of retina, corrected by concave lens Hyperopia (farsightedness) - focusing behind the retina, corrected by convex lens Prespbyopia – hardening of the lens due to aging (reduced accommodation), cannot have near vision, corrected by convex len. Astigmatism:- nonuniform curvature (in one axis), image blurred, corrected by cylindrical lens

  3. light (Cell bodies) (dendrites) Fovea: high spatial resolution Periphery: low spatial resolution

  4. Different cells in the retina The Basic Retinal Circuit Back of eye 6. Pigment cells 1. Receptor Cells (Graded potential) (input) 2. Bipolar Cells (Graded potential) 3. Ganglion Cells (action potential) (Output) 100 x 106 4. Horozontal Cells (Graded potential) 5. Amacrine Cells (Graded/action potential) 106 Convergence and divergence of connections Structure of the eye Front of eye 2

  5. Receptive field of RGC Microelectrode Stephen Kuffler

  6. Receptive field of RGC c a b

  7. Features of RGC center-surround interactions • There are two types of RFs: ON center/OFF surround, OFF center/ON surround. • Surround stimulation actively inhibits response to center stimulation; maximal response can be evoked only with an optimally sized spot.

  8. Receptive field • Definition: the area of the retina (or visual field) in which light signals evoke responses • It depends largely on the synaptic inputs to the cell, which in turn depends on dendritic field of the cell • Fovea: small RF (~0. 1o), high resolution; Periphery: large RF (3-5o), low resolution • (1o = 0.25 mm on the retina) • Ganglion Cell types: • M cells: large RF, fast response, color blind; • P cells: small RF, slower response, color sensitive.

  9. Center/surround RF explains some visual illusions Mach band

  10. More illusions… Hermann’s grid

  11. Center/surround RF also explains spatial frequency tuning

  12. M and P RGC cells have different spatial frequency selectivity

  13. Direct pathway: Photo receptor  Bipolar  RGC glutamate glutamate +: excitatory synapse, preserve response direction -: inhibitory synapse, flip response direction Direct pathway is responsible to the RF center

  14. How does glutamate activate or inhibit bipolar cells? • Off center bipolar cell – glutamate is excitatory, opens glutamate receptor-channel similar to the excitatory synapse. • On center biopolar cell – glutamate is inhibitory, opens K+ channel or closes cGMP-gated channel, by reducing cGMP through a metabotropic glutamate receptor (G-protein coupled receptor) that activate cGMP phosphodiesterase.

  15. Indirect pathway glutamate GABA Indirect pathway mediated by horizontal is responsible to the antagonistic RF surround There are other indirect pathway mediated by amacrine cells (use dopamine, ACh, indolamine)

  16. Summary of retinal circuit Direct pathway Indirect pathway + - Bipolar cell → amacrine cell →ganglion cell

More Related