Long - lasting , long - range detection

We examined the time course of threshold reduction in the Gabor lateral masking paradigm (Polat and Sagi 1993). Contrast detection thresholds were measured (2AFC) for a brieey presented (36 msec) foveal Gabor signal (GS), preceded by a presentation (90 msec) of two high-contrast GS anked masks, with Stimulus Onset Asynchrony (SOA) varying from 0 to 16,290 msec. Using target-to-mask separations of 3 and 12 (=0.15 , GS wavelength), the 3 separated GS masks enhanced target threshold by 0.25 log units at SOA=0 and by 0.17 log units at 2,700 msec. At 12 separation, threshold was enhanced by 0.11 log units at SOA=0 and by 0.14 log units at 2,700 msec. Long-range (12) and short-range (3) enhancements persisted for over 16 seconds. Delayed and simultaneous enhancement depended on the stimulus connguration (maximal for collinear target and masks), local parameters (orientation, spatial frequency, and phase), and the presented eye (dichoptic vs. monoptic). The results suggest that spatial lters in early vision retain an input trace far beyond the perceptual integration range. This trace may subserve the consolidation of lter activity into long-term memory.