June 2013
Volume 54, Issue 15
ARVO Annual Meeting Abstract  |   June 2013
Two Distinct Patterns of Input Exist Among ON Cone Bipolar Cells and Predict Their Spatial Responding
Author Affiliations & Notes
  • Robert Purgert
    Washington University in St. Louis School of Medicine, St. Louis, MO
  • Peter Lukasiewicz
    Washington University in St. Louis School of Medicine, St. Louis, MO
  • Footnotes
    Commercial Relationships Robert Purgert, None; Peter Lukasiewicz, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2013, Vol.54, 6157. doi:
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      Robert Purgert, Peter Lukasiewicz; Two Distinct Patterns of Input Exist Among ON Cone Bipolar Cells and Predict Their Spatial Responding. Invest. Ophthalmol. Vis. Sci. 2013;54(15):6157.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: Extraction of spatial information from visual scenes begins with the cone bipolar cell. They accomplish this via their antagonistic center-surround receptive fields, derived from inputs they receive from cones, horizontal cells, and amacrine cells. However, these inputs have not all been measured within single mammalian cone bipolar cells. In particular, the relative roles of inhibitory horizontal cell and amacrine cell input remain unknown. In this study, we assessed the magnitude of cone, horizontal cell, and amacrine cell current inputs within single ON cone bipolar cells (ON CBCs). Additionally, the physiological roles of the combined inputs were examined by measuring voltage responses.

Methods: Mouse ON CBC light responses were recorded with whole cell current- and voltage-clamp methods. Cone, horizontal cell, and amacrine cell inputs were isolated: clamping at Ecation isolated inhibitory amacrine cell inputs, while clamping at ECl +/- HEPES, a blocker of horizontal cell inhibition, isolated cone and horizontal cell inputs. Visual stimuli were drifting sine wave gratings displayed atop a rod-saturating background. Response data were fit with a difference-of-Gaussians model to derive the magnitudes and spatial extents of inputs.

Results: Inputs were measured from the same ON CBC. All cells had strong cone input, and weak horizontal cell input. However, they segregated based on the magnitude of amacrine cell input: it was strong in “S” cells, and weak in “W” cells. Voltage responses were recorded in a separate experiment to measure cells’ spatial response properties. All cells had robust responses to narrow-field stimuli. However, the suppression by wide-field stimuli differed and separated ON CBCs into two classes: “S” cells exhibited strong suppression (so-called strong spatial tuning), and “W” cells showed weak suppression (so-called weak spatial tuning). Fitting the data with a difference-of-Gaussians model revealed that summation of “S” current input data predicted the “S” voltage responses; “W” input data likewise predicted the “W” response data.

Conclusions: Our findings suggest that there are two classes of ON CBCs that exhibit distinct patterns of visual spatial processing. The differences are attributed to the strengths of amacrine cell input. To the best of our knowledge, this is first evidence of a functional division among ON CBCs in encoding spatial stimuli.

Keywords: 435 bipolar cells • 508 electrophysiology: non-clinical • 673 receptive fields  

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