limulus model

limulus model - Cell-Based Model of the Limulus Lateral Eye...

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Cell-Based Model of the Limulus Lateral Eye CHRISTOPHER L. PASSAGLIA, FREDERICK A. DODGE, AND ROBERT B. BARLOW Departments of Ophthalmology and Physiology, Center for Vision Research, State University of New York Health Science Center, Syracuse, New York 13210; and Marine Biological Laboratory, Woods Hole, Massachusetts 02543 Passaglia, Christopher L., Frederick A. Dodge, and Robert B. recently been used to study patterns of activity generated by Barlow. Cell-based model of the Limulus lateral eye. J. Neurophys- ensembles of retinal neurons, but neither technique has yet iol. 80: 1800–1815, 1998. We present a cell-based model of the proven practical for use with behaving animals. An alterna- Limulus lateral eye that computes the eye’s input to the brain in tive approach is to construct a realistic computational model response to any specified scene. Based on the results of extensive of the eye from anatomic and physiological data. Because physiological studies, the model simulates the optical sampling of of their relative simplicity, the eyes of lower vertebrates and visual space by the array of retinal receptors (ommatidia), the invertebrates appear to offer the best opportunities (Teeters transduction of light into receptor potentials, the integration of et al. 1997; Werblin 1991). The lateral eye of the horseshoe excitatory and inhibitory signals into generator potentials, and the crab, Limulus polyphemus, is a particularly attractive model conversion of generator potentials into trains of optic nerve im- pulses. By simulating these processes at the cellular level, model system because it processes visual information with rela- ommatidia can reproduce response variability resulting from noise tively few retinal receptors using integrative mechanisms inherent in the stimulus and the eye itself, and they can adapt to shared by many higher animals (Barlow 1969; Ratliff 1974), changes in light intensity over a wide operating range. Programmed and it extracts sufficient information from underwater scenes with these realistic properties, the model eye computes the simulta- to enable horseshoe crabs to find mates (Barlow et al. 1982). neous activity of its ensemble of optic nerve fibers, allowing us to Precise measurements of the animal’s visual performance explore the retinal code that mediates the visually guided behavior (Herzog et al. 1996; Powers et al. 1991) guide our studies of the animal in its natural habitat. We assess the accuracy of and provide important tests of model predictions. model predictions by comparing the response recorded from a Quantitative analyses of the Limulus eye began with the single optic nerve fiber to that computed by the model for the pioneering studies of Hartline and Ratliff (1957, 1958). corresponding receptor. Correlation coefficients between recorded and computed responses were typically ú 95% under laboratory Building on the discovery of lateral inhibition in this eye conditions. Parametric analyses of the model together with optic (Hartline 1949), they formulated a linear model of the eye’s
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limulus model - Cell-Based Model of the Limulus Lateral Eye...

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