The effects of tool holding on body schema during motor imagery: a near-infrared spectroscopy study

[Purpose] The purpose of this study is to assess the influence of tool holding on brain activities during motor imagery in two tasks: imagining the movement of writing the alphabet while holding a pen and without holding the pen. [Subjects and Methods] Eleven healthy right-handed adults performed two tasks, holding a pen and not holding the pen during imagining the movement of writing the alphabet using a pen. Regions of targets were Brodmann areas 6 which were a motor-related region, 44/45 and 39/40 which taken on the role of forming the body schema. Change of the oxygenation state of hemoglobin associated with brain activity were acquired using a near-infrared spectroscopy. [Results] When using their dominant right hands, task-related increases in oxy-Hb were prominent in Brodmann areas 44/45 and 39/40 when imagining writing while actually holding the pen than when not. When using the non-dominant left hands, there were no significant differences between the two conditions in the same areas. [Conclusion] These results suggest that the tool held can be incorporated into the body schema in the motor imagery of an automated tool use task. Therefore, tool holding during motor imagery might be more effectively influence during rehabilitation.