Across‐frequency impairment in seeing a temporal gap

Purpose To assess the effects of employing separate spatial frequencies for leading and trailing markers on detection of a temporal gap between the two markers. Methods Twelve normal observers were tested to measure gap detection thresholds. Gaussian‐windowed sinusoidal gratings were used for markers bounding a gap and thresholds were determined using an adaptive tracking procedure. Spatial frequencies of the leading and the trailing markers were orthogonally manipulated to be either 2 or 4 cpd. The trailing markers were tilted slightly clockwise from the vertical leading markers in order to isolate the effects of frequency change from those of pattern change. In separate blocks of trials, four combinations of the leading and trailing frequencies were tested. Results With markers of identical frequency, gap thresholds were higher for 4 cpd than for 2 cpd markers, replicating well‐established findings of impaired temporal resolution with increasing spatial frequency. Gap thresholds for markers of different frequencies were even higher than the 4‐cpd within‐frequency thresholds. Conclusions Seeing a temporal gap becomes difficult when spatial frequency change is introduced between gap markers. We propose that temporal processing across different spatial frequency channels leads to impaired gap detection.