Neuroanatomical organization of perceptual memory: an fMRI study of picture priming.

Neuroanatomical organization of perceptual representation in human memory system is unclear primarily because it has been studied using paradigms that have both, perceptual and conceptual components (e.g., word stem completion and word fragment completion). In the present experiment, functional magnetic resonance imaging (fMRI) technique was used to examine the pattern of cortical activation in a picture identification test in which subjects were asked to identify subliminally presented primed and novel pictures. This test is a modification of the word identification test that is considered a "pure" form of perceptual priming. Results indicate that perceptual priming is associated with reduced activation in the extrastriate cortex and that the memory for subliminally presented stimuli is processed by the same brain areas that process adequate stimuli. The activation pattern observed in picture identification test is different from that reported in the experiments of conceptual priming, suggesting that perceptual and conceptual representation of memory are supported by separate brain mechanisms.