Ventral premotor cortex lesions disrupt learning of sequential grammatical structures

Abstract

IntroductionRecent functional magnetic resonance imaging (fMRI) evidence shows differential involvement of the inferior frontal gyrus (IFG) and the ventral premotor cortex (PMv) in syntactic processing. Our main goal is to specify the precise role of the PMv in the processing of sequential structures and whether these processes are a necessary prerequisite for the successful acquisition of grammatical structure. MethodsWe tested patients with PMv lesions in an artificial grammar (AG) learning task, including correct sentences and sentences with violations of local (referring to adjacent elements within an AG string) and long-distance dependencies (incorporating recursive structures). In addition to performance measures event-related potentials to these violations were recorded. Results and conclusionsCompared to matched controls, patients displayed impaired acquisition of the AG. This impairment was more pronounced for local than for long-distance dependencies. This effect was paralleled by a selective reduction of the P600 component in response to violations of local dependencies. Most importantly, the P600 elicited by violations of long-distance dependencies was comparable between groups. Together, behavioral and ERP results indicate a PMv involvement in processing local sequential information.