Somatic sensation of hand-object interactive movement is associated with activity in the left inferior parietal cortex

Manipulation of objects and tool-use are known to be controlled by a network of frontal motor and parietal areas. Here, we investigate which of these areas are associated with the somatic sensation of hand-object interactive movement using functional magnetic resonance imaging. To dissociate the sensation of movement from the motor control commands, we used a new kinesthetic illusion. Twelve blindfolded right-handed participants placed the palm of their right or left hand on an object (a ball). Simultaneously, we vibrated the tendon of the wrist extensor muscle. This elicited the illusion that the wrist is flexing and the touched object is also moving along with the hand (hand-object illusion). As controls, we vibrated the skin surface over the nearby bone, which does not elicit any illusions, or we vibrated the tendon when the hand did not touch the object, which only generates the illusory flexion of the hand. We found that the hand-object illusion specifically activated the left inferior parietal lobule (IPL) (supramarginal gyrus and parietal operculum, including cytoarchitectonic areas ip1 and op1) and area 44. The left IPL was activated both during the hand-object illusions with the right and left hands, and the activity was greater than in the right corresponding parietal region, suggesting a dominant role of the left hemisphere. We conclude that the left IPL is involved in the somatic perception of hand-object interactive movement and suggest that the underlying mechanism is the somatic integration of internal information about the body and external information about the object.