P600

P600 is an event-related potential (ERP) component observed in electroencephalography (EEG) studies of language processing. It is a late positive deflection that typically peaks around 600 milliseconds after stimulus onset and is most prominent over centro-parietal scalp regions. The P600 is commonly elicited by syntactic processing demands and is particularly robust in response to syntactic violations or garden-path sentences that require reanalysis or repair of sentence structure.

The elicitation of the P600 often accompanies difficult or unexpected syntactic configurations, such as violations of grammar rules or structural ambiguities that force listeners or readers to revise initial interpretations. It can also appear in response to certain complex or inconsistent sentence structures and, under some conditions, to semantic anomalies. In the literature, the P600 is frequently contrasted with the N400, an earlier component more closely linked to semantic processing.

Interpretations of the P600 vary. Many accounts associate it with syntactic reanalysis or repair processes, integration of syntactic information into working memory, or general processing costs related to structural processing. Alternative views emphasize attentional or memory-related contributions, and some studies report P600-like effects in nonlinguistic domains, suggesting broader applicability to structured sequence processing. The precise interpretation can depend on experimental design and language.

Topographically, the P600 is usually observed as a posteriorly distributed effect, though its exact scalp distribution and latency can differ with modality (reading vs. listening), task demands, and individual differences. It has been documented across multiple languages and paradigms, making it a common tool for exploring how the brain processes syntax, linguistic complexity, and related cognitive functions.