Wrong or right? Brain potentials reveal hemispheric asymmetries to semantic relations during word-by-word sentence reading as a function of (fictional) knowledge.

How does individual-level variation in experience and knowledge influence neural mechanisms important for real-time language comprehension? We used event-related brain potentials (ERPs) combined with lateralized visual field (VF) presentation of sentence-final words to examine asymmetries in hemispheric processing as individuals who varied in their knowledge of the fictional world of Harry Potter (HP) read sentences about general topics and HP. HP sentence endings were either contextually supported, unrelated anomalies, or semantically related anomalies. Amongst HP experts, we observed contextual support effects with presentation to both left and right VFs, but related anomaly effects only with presentation to the left VF (right hemisphere). Our findings are in line with accounts in which the left hemisphere (LH) activates relatively narrow/specific semantic information and the RH activates a broader range of semantic relations, including those relating to the construction of mental/situation models, as individuals attempt to comprehend sentences, one word at a time. We suggest that RH-biased hemispheric asymmetries in processing related (but linguistically inappropriate) words in written sentences may emerge as a function of each individual's degree of relevant knowledge. We tentatively hypothesize that content experts may optimize hemispheric differences in scope of semantic activation to maximize both precision (in the LH) and flexibility (in the RH) during language comprehension.