The motor system (partially) deceives body representation biases in absence of visual correcting cues.

The internal models of our body dimensions are prone to bias, but little evidence exists to explain how the motor system achieves fine-grained control despite these distortions. Previous work showed that the hand representation, assessed in a dynamic task (Proprioceptive Matching Task), was less distorted compared to that measured through a static body representation task (Localization Task), suggesting that either the hand representation was updated or the motor trajectory was adjusted during movement. The present study set out to shed light on this phenomenon by administering the Localization Task before and after either the Proprioceptive Matching Task or a control condition in a within-subjects design. Our results showed that hand map biases decreased during the Proprioceptive Matching Task, but that this increase in accuracy did not carry over to the Localization Task. In other words, more accurate performance in the dynamic body representation task does not reflect a change in how the hand is represented. Rather, it likely reflects a refinement of the motor trajectory, due to the integration of multisensory information, providing interesting insights into how the motor system partially overcomes biases in body representations.