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Separability of stimulus parameter encoding by on-off directionally selective rabbit retinal ganglion cells.

Abstract

The ganglion cell output of the retina constitutes a bottleneck in sensory processing in that ganglion cells must encode multiple stimulus parameters in their responses. Here we investigate encoding strategies of On-Off directionally selective retinal ganglion cells (On-Off DS RGCs) in rabbits, a class of cells dedicated to representing motion. The exquisite axial discrimination of these cells to preferred vs. null direction motion is well documented: it is invariant with respect to speed, contrast, spatial configuration, spatial frequency, and motion extent. However, these cells have broad direction tuning curves and their responses also vary as a function of other parameters such as speed and contrast. In this study, we examined whether the variation in responses across multiple stimulus parameters is systematic, that is the same for all cells, and separable, such that the response to a stimulus is a product of the effects of each stimulus parameter alone. We extracellularly recorded single On-Off DS RGCs in a superfused eyecup preparation while stimulating them with moving bars. We found that spike count responses of these cells scaled as independent functions of direction, speed, and luminance. Moreover, the speed and luminance functions were common across the whole sample of cells. Based on these findings, we developed a model that accurately predicted responses of On-Off DS RGCs as products of separable functions of direction, speed, and luminance (r = 0.98; P < 0.0001). Such a multiplicatively separable encoding strategy may simplify the decoding of these cells' outputs by the higher visual centers.

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    • Authors

    Nowak P, Dobbins AC, Gawne TJ, Grzywacz NM, Amthor FR

    Institution

    Department of Vision Sciences, University of Alabama at Birmingham, Birmingham, AL 35294-1170, USA.

    Source

    Journal of neurophysiology 105:5 2011 May pg 2083-99

    MeSH

    Action Potentials
    Animals
    Female
    Male
    Motion Perception
    Photic Stimulation
    Rabbits
    Retinal Ganglion Cells
    Visual Fields

    Pub Type(s)

    Comparative Study
    Journal Article
    Research Support, N.I.H., Extramural
    Research Support, Non-U.S. Gov't
    Research Support, U.S. Gov't, Non-P.H.S.

    Language

    eng

    PubMed ID

    21325684