Human inferior parietal cortex 'programs' the action class of grasping

If one writes with a pen grasped between the toes, or a pencil held in the mouth, the handwriting style may be of poor quality but can be identified as belonging to a particular individual. Like other actions, such as grasping or pointing, different body parts can be used to produce the movement. These findings, of reasonably consistent spatial and temporal productions by different effectors, have been used to argue for the concept of motor equivalence and the existence of motor programs abstracted from particular effectors. In this study subjects were required to perform an action (grasping a sweet) with different effectors (the mouth or the hand) while the brain was scanned. Activation of the inferior parietal lobe during real and imagined mouth grasping, and during real hand grasping actions was demonstrated. Primate neurophysiological research has implicated this region in a movement-planning role. Our results confirm the importance of the inferior parietal lobe in integrating converging multimodal sensory information for coding of general action patterns in humans.