A mid-central N450 component of the ERP distinguishes trial-by-trial effects of target familiarity and context strength

N400-like components in the ERP are commonly understood as being inversely related to the degree at which contextual factors have prepared the brain for the processing of meaningful stimuli. Here we show independent and systematic effects of familiarity and context on mid-central N450 in a simple visual priming task. Participants selected a target digit defined by color while ignoring a distractor digit. Pairs of two subsequent displays (prime, probe) were considered. Probe target familiarity could be high (prime–probe target repetition), low (novel probe target), or very low (probe target = prime distractor). Context strength depended on history of the probe distractor and could be high (prime–probe distractor repetition), low (novel probe distractor), or very low (probe distractor = prime target). The seven priming conditions showed exactly the predicted order of N450 amplitude, with largest N450 for strong context/low target familiarity and smallest N450 for weak context/high target familiarity. Results significantly broaden the view of N400, as a universal marker of stimulus familiarity and context strength also in basic, non-linguistic settings.

► May substantially broaden our perspective on the N400 family of ERP components.
► Mid-central N450 effects from very simple visual stimuli (digits) in a priming task.
► Reports a complex but systematic pattern of priming effects on N450 amplitude.
► Puts forward a novel two-factor model of N400-like effects.
► Two basic factors identified; target familiarity and context strength.