Interhemispheric interplay between the left and right premotor cortex during grasping as assessed by dynamic causal modelling

Research on the contribution of the ipsilateral hemisphere to unilateral movements, and how it is mediated by transcallosal connections, has so far provided contradictory findings. By using dynamic causal modelling (DCM) and Parametric Empirical Bayes analyses applied to fMRI data, we sought to describe effective connectivity during pantomimed and imagined right-hand grasping within the grasping network, namely the anterior intraparietal sulcus, ventral and dorsal (PMd) premotor cortex, supplementary motor area and primary motor cortex (M1). The two-fold aim of the present work was to explore a) whether right and left parieto-frontal areas show similar connectivity couplings, and b) the interhemispheric dynamics between these regions across the two hemispheres. We detected a network architecture comparable across hemispheres during executed but not imagined grasping movements. Furthermore, during pantomimed grasping the interhemispheric crosstalk was mainly driven by premotor areas: we found an inhibitory influence from the right PMd toward the left premotor and motor areas and excitatory couplings between homologous ventral premotor and supplementary motor regions. Overall, our results support the view that dissociable components of unilateral grasping execution are encoded by a non-lateralized set of brain areas complexly intertwined by interhemispheric dynamics, whereas motor imagery obeys different principles.

Automated summary

By using dynamic causal modelling and Parametric Empirical Bayes analyses applied to fMRI data, this study found that the connectivity patterns between bilateral regions in the grasping network are similar during executed grasping movements. However, during pantomimed grasping, interhemispheric crosstalk is mainly driven by premotor areas, with inhibitory influences from the right PMd towards the left premotor and motor areas and excitatory couplings between homologous ventral premotor and supplementary motor regions. Overall, the results suggest that unilateral grasping execution involves a non-lateralized set of brain areas complexly intertwined by interhemispheric dynamics, while motor imagery follows different principles.