Attention and short-term memory in contrast detection

Low-contrast visual stimuli have been found to produce a memory trace, enhancing subsequent target detection for as much as 16 s. Here we show that the memory trace depends on dynamic interactions between low-level stimulus properties and a higher-level gating process. Detection of vertical targets (Gabor signals) was enhanced by preceding vertical Gabor primes, but suppressed by preceding tilted primes--pointing to a competitive process of dynamic resource allocation. The priming effect was also dependent on a temporal cue, activating a sensory gating process with maximal effect at 300-500 ms delay. The results suggest a two-step process in which attention affects transition between perception and memory: a non-selective gating process followed by competition between overlapping representations.