Masked word repetition results in increased fMRI signal: a framework for understanding signal changes in priming.

Evidence from multiple paradigms has converged on the finding that stimulus repetition most often results in decreases in neural activity. The mechanisms of these decreases, however, are not yet well understood. The current study attempted to determine, through the use of masked word repetition priming, whether decreases in activity levels occur in response to pre- or post-prime identification processes. fMRI was performed while participants engaged in a lexical decision task where words were primed with a briefly presented and masked word. Masked word priming resulted in increased fMRI signal in regions of cortex associated with the perceptual identification of the target words. This finding provides evidence suggesting that the impact of repetition priming on the fMRI signal may depend upon whether or not the prime is identified.