Evidence for 40-Hz oscillatory short-term visual memory revealed by human reaction-time measurements

Four experiments show that presentation of a synchronous premask frame with in a 40-Hz, flickering premask matrix primes subsequent detection of a Kani zsa-type square by generation of a 40-Hz prime. Reaction time (RT) priming effects indicated a 150-200-ms prime duration following premask display. RT s were also found to be sensitive to the phase relationship between offset of the premask display relative to the onset time of the target: Priming ef fects were maximal when the target was presented out of phase with premask presentation (i.e., at interstimulus intervals displaced by 180 degrees rel ative to the 40-Hz rhythm of premask-frame presentation). Taken together, t hese results demonstrate the existence of a very short-term visual memory t hat oscillates at 40 Hz. The findings are discussed in the context of compl ementary psychological and neurophysiological findings related to visual-ob ject coding and the role of gamma-band activity in the brain.