The dynamics of operations in visual memory: a review and new evidence for oscillatory priming

Evidence from neurophysiological studies indicates that the synchronization of distributed neuronal assemblies in the gamma frequency range is responsible for the integration of discrete stimulus components into coherent wholes (e.g., see Singer, 1999 for review). Psychophysical support for this hypothesis has been reported in experiments that demonstrate that the presentation of a synchronous-premask frame within a 40-Hz flickering premask matrix primes the subsequent detection of a target Kanizsa-type square by generation of a 40-Hz prime (Elliott & Müller, 1998). Psychopharmacological and electrophysiological evidence suggests that this priming mechanism is related to activity in interneuronal networks and relies on the combined function of prefrontal and posterior circuits. In addition, psychophysical experiments demonstrate the existence of a prime-specific visual short-term memory that oscillates at 40 Hz and remains functional for up to 300 ms post-stimulus offset. These results are consistent with a view of the prime as a form of oscillatory mechanism, related to the persistence of visual information (Coltheart, 1980) and in the capacity guided by (prefrontal) top-down influences upon visual-cortical function.