Intermanual transfer characteristics of dynamic learning : 1 direction ,

Abbreviated Title 8 Intermanual transfer characteristics of dynamic learning 9 Abstract 19 Intermanual transfer, i.e., generalization of motor learning across hands, is a well-accepted phenomenon of 20 motor learning. Yet, there are open questions regarding the characteristics of this transfer, particularly, 21 intermanual transfer of dynamic learning. In this study, we investigated intermanual transfer in a force field 22 adaptation task concerning the direction and the coordinate frame of transfer as well as the influence of a 24 h 23 consolidation period on the transfer. We tested 48 healthy human subjects for transfer from dominant to non-24 dominant hand and vice versa. We considered two features of transfer. First, we examined transfer to the 25 untrained hand using force channel trials that suppress error feedback and learning mechanisms to assess 26 intermanual transfer in form of a practice-dependent bias. Second, we considered transfer by exposing the 27 subjects to the force field with the untrained hand to check for faster learning of the dynamics (interlimb 28 savings). Half of the subjects was tested for transfer immediately after adaptation, whereas the other half was 29 tested after a 24 h consolidation period. Our results showed intermanual transfer both from dominant to non-30 dominant hand and vice versa in extrinsic coordinates. Following the consolidation period, transfer effects were 31 weakened. Moreover, the transfer effects were negligible compared to the subjects' ability to rapidly adapt to the 32 force field condition. We conclude that intermanual transfer is a bidirectional phenomenon that vanishes with 33 time. However, the ability to transfer motor learning seems to play a minor role compared to the rapid adaptation 34 processes. 35