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Christopher Fortenbach, Marie E Burns; Distinct bipolar cell subtypes carry parallel streams of temporal information under scotopic conditions. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1762.
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© ARVO (1962-2015); The Authors (2016-present)
Visual signal processing begins at the bipolar cell within the retina. Rods, which are responsible for vision in scotopic conditions, form direct chemical synapses with rod bipolar cells and signal indirectly to a dozen subtypes of cone bipolar cells. Cone bipolar cells display distinct temporal properties when stimulated directly by cones. Given that the photoresponses of rods are significantly slower than cones and that this limits the ability of rods to convey high frequency visual information to second-order retinal neurons, it remains unknown whether rod-driven visual signal separates into parallel channels carrying distinct temporal information at the level of the bipolar cell.
Whole-cell recordings of rods, rod bipolar cells, cone bipolar cells, and AII amacrine cells were performed in dark-adapted mouse retina slices. Voltage-responses were elicited by calibrated flashes and sinusoidal flickering stimuli. Light-evoked flicker responses were then subjected to Fourier analysis to extract both the magnitude and phase of the cellular response at the stimulus frequency. Following recording, slices were subject to immunohistochemical analysis to determine bipolar cell subtype.
At the scotopic intensities investigated, each class of cell displayed low-pass frequency tuning with different bipolar cell subtypes displaying different characteristic cutoff frequencies and phase shifts. Some bipolar classes showed improved temporal performance as background intensities increased. The temporal performance of individual bipolar cell subtypes was further impacted by the addition of strychnine, which blocks glycinergic signaling in the retina. In the presence of DNQX, which blocks synaptic output from rod bipolar cells, rod bipolar cells displayed smaller flicker magnitudes and a reduced ability to convey high-frequency information.
Rod-driven responses within the retina separate into parallel channels with distinct temporal properties at the level of the bipolar cell. Visual information conveyed by these channels is influenced by feedback within the inner retina in a subtype-dependent manner, which can further shape their temporal performance.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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