The effect of luminance decrements upon the detection of sinusoidal gratings

Abstract

Observers detected 20-msec sinusoidal gratings presented at various asynchronies relative to a decrement in the mean luminance of a uniform field. Brief luminance decrements have no effect upon contrast thresholds determined with high-spatial-frequency gratings. With low-spatial-frequency gratings, transient threshold elevations were found at decrement onset and offset. For longer decrements, threshold changes were found for both high- and low-spatial-frequency gratings. However, the time courses of these changes differed. With high-spatial-frequency gratings, thresholds changed more gradually, whereas with low-spatial-frequency gratings, the time courses contained marked transients at the onset and offset of the decrement. These results are discussed in terms of contribution of multiple spatial-frequency channels to temporal resolution. © 1984 Psychonomic Society, Inc.