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TA Münch, SI Fried, FS Werblin; Starburst Cells Initiate Directional Selective Responses in Rabbit Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2981.
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Purpose: Our goal was to show that directional selective responses in the retina are mediated by an asymmetry in the response of starburst cells to directions of movement and by an asymmetry in the connections between starburst cells and directional selective (DS) ganglion cells. Methods: Cells were studied in the isolated whole-mount rabbit retina with whole-cell patch clamp. Light responses of starburst cells at the soma were compared as an annular stimulus centered on the cell body expanded or contracted. In double patch experiments, excitation and inhibition were measured in DS cells in response to current injected into neighboring starburst cells. Results: An annular light stimulus caused a stronger depolarization at the soma when it expanded (therefore moving from the soma towards the periphery) than when it contracted (from periphery to soma). In double patch experiments, the polarity of response of DS cells depended on the relative position of the stimulated starburst cell. Stimulating a starburst cell on the NULL side of the DS cell elicited mostly inhibitory currents in the DS cell, while stimulating a starburst cell on the PREF side elicited mostly excitatory currents. Conclusions: Our results suggest (A) that starburst cells release more transmitter when a stimulus moves towards the tips of the processes. Therefore, a stimulus moving across the cell, for example from left to right, would cause more transmitter release from the right processes than from the left processes. In addition, our double patch results suggest (B) that a DS cell with a preferred direction from left to right receives excitation from right processes of starburst cells and inhibition from left processes. Thus, a population of starburst cells spanning the dendritic field of a DS cell (each starburst cell expressing directional asymmetric release as well as left-right-asymmetric connectivity) would endow that DS cell with left-right directional selectivity. This would require that each DS cell selects excitation and inhibition from specific starburst cell processes aligned along its preferred-null-axis. View OriginalDownload SlideView OriginalDownload Slide
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