Processing of task-irrelevant words of different frequency values: a visual mismatch negativity study.

This study examined electrophysiological correlates of early and automatic word access. Chinese single-character words of high frequency and low frequency were peripherally presented in an oddball paradigm. Participants were instructed to carry out a centrally presented nonlinguistic colour-tracking task and ignore the lexical stimuli presented on both sides. Early visual mismatch negativity (vMMN) effects at 120-150 and 200-300 ms were elicited only by high-frequency characters, whereas low-frequency characters yielded vMMN only after 300 ms. This contrast of vMMN effects indicating lexical processing in an attention-deprived condition is suggested to result from stronger memory traces for high-frequency characters in comparison with low-frequency characters.