Visual Feedback Decoding During Bimanual Circle Drawing

The between-hand interference during bimanual tasks is a consequence of the connection between the neural controllers that plan the upper extremities’ movements. Previous studies showed the existence of an asymmetric between-hand interference (caused by neural crosstalk) when different kinematics plans were to be executed by each hand. Nevertheless, little is known about between-hand interference/cooperation when one hand is visually guided with composite feedback (i.e., a weighted sum of both hand positions). Here we investigated the central nervous system’s (CNS) ability to decode the position information of an invisible hand from composite feedback. We designed a continuous bimanual circle drawing with only one hand operated under visual feedback (e.g., guided with actual/altered feedback). Our results demonstrated a significant decrease in the invisible non-dominant hand (NDH) deviation from the displayed trajectory and a decrease in the distance between centers of the traced and displayed circles when composite feedback was presented on the dominant hand (DH) motion. In contrast, when NDH was visually guided, DH performance deteriorated. This indicates the CNS’s unidirectional ability to decode the position of the invisible NDH from the composite feedback. Also, when DH/NDH was visually guided with amplified error feedback, the invisible contralateral side performance degraded, with visually-guided DH having a greater impact on NDH, supporting the asymmetry of interference. Comparing muscle activations, we concluded that the observed kinematic differences were not due to alternation in muscle co-contractions. Findings are discussed in the context of decoding ability, neural crosstalk, and functional lateralization theory.