03_RGCs Questions - MCB 167 Discussion assignment for...

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Unformatted text preview: MCB 167 Discussion assignment for Friday, Feb 19 Direction Selectivity in Mammalian Retina Reading : Yoshida K, Watanabe D, Ishikane H, Tachibana M, Pastan I, Nakanishi S. A key role of starburst amacrine cells in originating retinal directional selectivity and optokinetic eye movement. Neuron. 2001 Jun;30(3):771‐80. Reading guide. Please read the entire paper. You should already be familiar with ON‐OFF direction selective ganglion cells from lecture. If you want more background on the properties of these cells, read Barlow HB & Levick WR, J. Physiol. 178: 477‐504, 1965. An important fact guiding the experiment design is that all retinal ganglion cells that show combined ON‐OFF responses are direction selective. Another important fact is that starburst amacrine cells receive glutamatergic input from bipolar cells, and provide the major source of GABAergic input, and the sole source of cholinergic (ACh) input, to retinal ganglion cells. Please answer the following questions with a paragraph each, and bring your answers to section. Question 1. How do the authors ensure that they only eliminate starburst amacrine cells? Why is this critical for the experiment? Why did they use an immunotoxin, rather than killing or inactivating these cells directly with a transgenically expressed protein under the mGluR2 promoter? Question 2. What was the effect of starburst amacrine cell deletion on direction selectivity of ON‐OFF retinal ganglion cells? What result do you think they would have obtained if they deleted ON bipolar cells or OFF bipolar cells, instead of starburst amacrine cells? Question 3. What is optokinetic nystagmus (aka the optokinetic reflex)? Why do you think starburst amacrine cell deletion disrupted the optokinetic response, but not the pupillary constriction reflex? ...
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This note was uploaded on 04/05/2010 for the course MCB 167 taught by Professor Feldman during the Spring '10 term at University of California, Berkeley.

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