Repeated Exposure to "meaningless" Pseudowords Modulates LPC, but Not N(FN)400.

Training readers to recognize pseudowords could decrease the processing differences between them and real words while clarifying the lexical acquisition processes. We analyze the effect of pseudoword repetition through the recording of EEG during a lexical decision task. Results showed a functional dissociation between two well-known ERP components: FN400 (Frontal N400, traditionally related to semantic processes) and LPC (Late Positive Complex, related to memory processes). On the one hand, FN400 was unaffected by pseudoword repetition and showed the typical lexicality effect. On the other hand, topographic and neural source analyses showed that LPC amplitude increased across repetitions, causing the lexicality effect to disappear, with the left inferior frontal, left superior temporal and right superior frontal gyri identified as the most likely neural sources. The lack of repetition effect on FN400 suggests that this component is unrelated to familiarity processes and is only influenced by semantic differences between stimuli. The LPC observations, however, reflect the construction and strengthening of visual memory traces for repeated pseudowords, facilitating their processing over the course of the task.