EN
INTRODUCTION: Using tools according to their functions requires parallel signal processing in numerous and specialized brain areas. So far, fMRI research on neural substrates underlying interactions with tools was mostly restricted to unimanual, pantomimed tool use. AIM(S): The scope of this project was to establish whether representations involved in planning bimanual grasps and subsequent usage of real tools can be distinguished from their functionally equivalent unimanual counterparts. Moreover, we addressed a question whether neural activity within the praxis representation network (PRN), responsible for transforming intentions into actions, is modulated by the number of effectors (hands) required to prepare the appropriate action towards a tool (e.g., a functional grasp). METHOD(S): FMRI contrasts, including repeated-measures ANOVAs and a region-of-interests approach, was adopted. 20 right‑handed participants were scanned in two separate sessions involving a leading vs. a non‑leading/supporting hand. The task was to interact – plan, grasp and execute an action – with bimanual and unimanual tools, and control objects. RESULTS: The greater engagement of the right superior parietal lobule (SPL) suggests that the primary aspect of bimanuality is coordination. Complex motor-to-mechanical transformations for such synchronized movements take place even before grasp and usage onsets. Although PRN was not modulated by tool manuality, SPL was also involved in initiating interactions with bimanual tools. Finally, as the task progressed from the planning to execution, the processing was more extensive and required more neural resources, peaking at the moment of the functional grasp. CONCLUSIONS: Even common actions such as grasping bimanual tools have to be preceded by multifaceted neural signal processing. Furthermore, the brain mechanisms underlying these actions are planned well before the actual behavioral performance of a task. FINANCIAL SUPPORT: Supported by NCN Maestro 2011/02/A/HS6/00174 to GK.