Tool-use induces functional updating of the body schema
Lucilla Cardinali, Francesca Frassinetti, Claudio Brozzoli, Christian Urquizar, Alice C. Roy, Alessandro FarnÃ¨
Time: 2009-06-30 04:50 PM – 05:10 PM
Last modified: 2009-06-04
To control bodily movements the human brain relies on a somatic representation termed body schema (BS). The almost one-century-old hypothesis that tool-use induces plastic changes resulting in the tool being incorporated in the BS is nowadays widely accepted. Whether tool-incorporation truly occurs remains unknown, however, as tool-use has never been shown to affect ensuing arm motor behavior. Here we report that using a mechanical grabber that physically extends the arm, alters the kinematics of subsequent free-hand grasping movements. Consistent with incorporation of the tool length in the BS, the tool-use-dependent differences in kinematics fit those naturally existing when comparing actions performed by subjects with longer vs. shorter arms. Remarkably, the tool-use after-effect was shown to generalize to pointing movements, despite no specific tool-training. These findings not only provide the first evidence that tool-use alters the body schema, but also reveal that what is modified is the somatic representation of intrinsic properties of the body morphology.