Finding meaning in novel geometric shapes influences electrophysiological correlates of repetition and dissociates perceptual and conceptual priming.

Repeatedly viewing an object can engender fluency-related implicit memory for perceptual and conceptual attributes, as indexed in tests of perceptual and conceptual priming, respectively. Stimuli with minimal pre-experimental meaning allow direct comparisons between these two types of priming and explorations of whether corresponding neural mechanisms differ. We therefore examined electrophysiological correlates of perceptual and conceptual priming for minimalist geometric shapes (squiggles). Response time measures of conceptual priming were evident for squiggles rated by individual subjects as most meaningful, but not for those rated least meaningful. Conceptual-priming magnitude was proportional across individuals to the amplitude of FN400 brain potentials, but only for meaningful squiggles. Perceptual priming was evident for squiggles irrespective of meaningfulness, and perceptual-priming magnitude was proportional to the amplitude of frontal P170 potentials. These findings therefore show that a single exposure to a novel stimulus can lead to neural processing accompanying conceptual priming that is distinct from that accompanying perceptual priming (FN400 potentials vs. P170 potentials, respectively). Overall, this evidence is also relevant to the current debate over the neural correlates of familiarity-based recognition, and runs counter to the prominent supposition that familiarity can be generically indexed by FN400 potentials. Copyright (c) 2009 Elsevier Inc. All rights reserved.