Perceptual priming enhances the creation of new episodic memories.

In recent years, most studies of human memory systems have placed the emphasis on differences rather than on similarities. The present study sought to assess the impact of perceptual priming on the creation of new episodic memories. It was composed of three distinct experimental phases: (1) an initial study phase, during which the number of repetitions of target words was manipulated; (2) a perceptual priming test phase, involving both target and new control words, which constituted the incidental encoding phase of (3) a subsequent Remember/Know/Guess recognition task. Results showed that the greater the perceptual priming at encoding, the more the episodic memory performance was enhanced, whereas no such relation was found for know judgments or feeling of familiarity. Furthermore, the words that were associated with the creation of new episodic memories had been perceptually primed to a greater extent during the incidental encoding phase than the words that were subsequently judged to be known or forgotten. These results suggest that the perceptual contents of episodic memories are constituted by the very perceptual representations that generate priming effects. Potential mechanisms linking perceptual priming to the creation of episodic memories are discussed.

Visual priming within and across symbolic format using a tachistoscopic picture identification task: a PET study.

The present work was aimed at characterizing picture priming effects from two complementary behavioral and functional neuroimaging (positron emission tomography, PET) studies. In two experiments, we used the same line drawings of common living/nonliving objects in a tachistoscopic identification task to contrast two forms of priming. In the within-format priming condition (picture-picture), subjects were instructed to perform a perceptual encoding task in the study phase, whereas in the cross-format priming condition (word-picture), they were instructed to perform a semantic encoding task. In Experiment 1, we showed significant priming effects in both priming conditions. However, the magnitude of priming effects in the same-format/perceptual encoding condition was higher than that in the different-format/semantic encoding condition, while the recognition performance did not differ between the two conditions. This finding supports the existence of two forms of priming that may be subserved by different systems. Consistent with these behavioral findings, the PET data for Experiment 2 revealed distinct priming-related patterns of regional cerebral blood flow (rCBF) decreases for the two priming conditions when primed items were compared to unprimed items. The same-format priming condition involved reductions in cerebral activity particularly in the right extrastriate cortex and left cerebellum, while the different-format priming condition was associated with rCBF decreases in the left inferior temporo-occipital cortex, left frontal regions, and the right cerebellum. These results suggest that the extrastriate cortex may subserve general aspects of perceptual priming, independent of the kind of stimuli, and that the right part of this cortex could underlie the same-format-specific system for pictures. These data also support the idea that the cross-format/semantic encoding priming for pictures represents a form of lexico-semantic priming subserved by a semantic neural network extending from left temporo-occipital cortex to left frontal regions. These results reinforce the distinction between perceptual and conceptual priming for pictures, indicating that different cerebral processes and systems are implicated in these two forms of picture priming.