The dorsal premotor cortex orchestrates concurrent speech and fingertapping movements

Human speech and hand use both involve highly specialized complex movement patterns. Whereas previous studies in detail characterized the cortical motor systems mediating speech and finger movements, the network that provides coordination of concurrent speech and hand movements so far is unknown. Using functional magnetic resonance imaging (fMRI), the present study investigated differential cortical networks devoted to speech or fingertapping, and regions mediating integration of these complex movement patterns involving different effectors. The conjunction contrasts revealing regions activated both during sole fingertapping and sole repetitive articulation or reading aloud showed contralateral regions at the border of ventral and dorsal motor cortex. In contrast, the analyses revealing regions showing a higher level of fMRI activation for concurrent movements of both effectors compared with sole hand movements or repetitive articulation or reading aloud showed distinct premotor activations, which were situated dorsal and caudal to the areas activated across speech and fingertapping tasks. These results indicate that the premotor cortex (PMC) subserves coordination of concurrent speech with hand movements. This integrative motor region is not identical with the area that shows overlapping activations for speech and fingertapping. Thus, concurrent performance of these complex movement patterns involving different effectors requires, in addition to somatotopic motor cortex activation, orchestration subserved by a distinct PMC area.