An event-related neuroimaging study distinguishing form and content in sentence processing

Two coordinated experiments using functional Magnetic Resonance Imaging (fM RI) investigated whether the brain represents language form (grammatical st ructure) separately from its meaning content (semantics). While in the scan ner, 14 young, unimpaired adults listened to simple sentences that were eit her nonanomalous or contained a grammatical error (for example, *Trees can grew.), or a semantic anomaly (for example, *Trees can cat.). A same/differ ent tone pitch judgment task provided a baseline that isolated brain activi ty associated with linguistic processing from background activity generated by attention to the task and analysis of the auditory input. Sites selecti vely activated by sentence processing were found in both hemispheres in inf erior frontal, middle, and superior frontal, superior temporal, and temporo -parietal regions. Effects of syntactic and semantic anomalies were differe ntiated by some nonoverlapping areas of activation: Syntactic anomaly trigg ered significantly increased activity in and around Broca's area, whereas s emantic anomaly activated several other sites anteriorly and posteriorly, a mong them Wernicke's area. These dissociations occurred when listeners were not required to attend to the anomaly. The results confirm that linguistic operations in sentence processing can be isolated from nonlinguistic opera tions and support the hypothesis of a specialization for syntactic processi ng.