Event-related potential indices of masked repetition priming

Two experiments sought to identify event-related potential (ERP) correlates of masked repetition priming of words in lists and to verify that such effects are not due to brief prime durations. In Experiment 1, prime stimuli were masked and their durations were individually titrated for each participant. Targets that were immediate or delayed repetitions of masked primes resulted in attenuation of the N400, with little or no enhancement of a late positive component (LPC). Delayed, in-the-clear repetitions of unmasked targets led to attenuation of the N400 and enhancement of the LPC. Experiment 2 used similar stimulus timing parameters, but primes were unmasked. More typical unmasked repetition effects were observed for immediate repetitions including a larger attenuation of the N400 and enhancement of the LPC. These findings are discussed within current notions of the functional significance of the N400 and LPC.