Neural and kinematic evidence of reach and grasp motor behavior in individual and social contexts

Despite decades of research, the crosstalk between human parietal and frontal brain regions subserving visually guided hand-object interactions is still to be solved. By applying effective connectivity analyses to functional magnetic resonance imaging (fMRI) data collected during the execution of visuomotor tasks, we described the functional organization of action- and effector- specific parietofrontal networks, providing evidence of an excitatory parieto-frontal modulation and inhibitory fronto-parietal feedback. This pattern was shared across hemispheres during unilateral movements, but was absent during motor imagery, likely due to the absence of an efferent copy driven by the execution of the movement. We next tested the hypothesis that these feedforward/feedback loops deal with the online monitoring of actions, and evaluated whether this process is modulated by social interactions. To this end, we implemented a virtual reality reach-to-grasp task involving the interaction with a virtual partner. In a subset of trials (30%), participants were forced to change their ongoing movement trajectory in response to unpredictably changing social or non-social cues. The combination of kinematic analyses, behavioral measures and neuroimaging data will provide unique insights on adaptive motor control. This collection of evidence will be framed in the context of novel frontiers in the study of visuomotor functions.