The neural mechanisms that underlie familiarity memory have been extensively investigated, but a consensus understanding remains elusive. Behavioral evidence suggests that familiarity sometimes shares sources with instances of implicit memory known as priming, in that the same increases in processing fluency that give rise to priming can engender familiarity. One underappreciated implication of this account is that patterns of neural activity that appear to index familiarity in a generic sense may instead reflect fluency-related precursors of recognition. In a novel illustration of this principle, we examined brain potentials during recognition tests for visual words. In two experiments, fluency was selectively enhanced for half of the test cues via masked repetition priming. Replicating previous findings, the proportion of words endorsed as "old" was greater for words immediately preceded by a matching masked word versus an unrelated one. In addition, N400 potentials were more positive for test cues preceded by matching versus unrelated masked words. Similar N400 differences were observed when false alarms were compared to correct rejections for the subset of unstudied words that were preceded by matching masked words. These N400 effects were topographically dissociable from other potentials that correlated with familiarity for studied words. We conclude that experiences of familiarity can have different neural correlates that signal the operation of distinct neurocognitive precursors of recognition judgments. Conceptualizations of the neural basis of recognition memory must account for a plurality of mechanisms that produce familiarity memory.
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