Larger receptive fields revealed using Battenberg stimuli to assess contrast summation with moving patterns

Abstract

This study reevaluated the summation extent formoving stimuli using the Battenberg summation paradigm(Meese, 2010),whichaims tocircumvent internalnoisechangeswith increasing stimulus size by holding display size constant. In the checkerboard stimulus, the size of the checks (luminance-modulated drifting gratings) was varied to measure dependence on signal area. Experiment 1 was a contrast detection task that used either signal checks alternating with uniform, mean luminance, checks (singlemotion) or alternate checks containing gratings moving in opposite directions (opposing-motion). The latter was designed to test whether summation extent changes when segregating regions based on motion direction. Results showed summation over a square summation area with a side length of 3.338,much larger than previous estimates of less than 18 for similar stimuli (Anderson & Burr, 1991). This was found for both motion combinations, providing no evidence that summation extent differs when segregating patternsbasedondirection,at contrastdetectionthreshold. Theseresults arein closeagreementwiththoseobtainedfor static patterns (Meese, 2010) and support the same underlying summationmodel. Experiment 2was a contrast increment detection task conducted to determine whether differencesinsummationextent ariseunder suprathreshold contrast conditions.Therewas nodependence oncheck size for either condition across the range of sizes tested. This supports the suggestion that segmentation mechanisms dominate perception under high-contrast conditions, a potential adaptive strategy employed by the visual system.