Summary and Conclusions:

1. Reaching movements made in a rotating room generate Coriolis forces that deviate the trajectory of the arm causing it to miss the target endpoint. With repeated reaching movements during rotation, the path of the arm rapidly becomes progressively straighter and endpoint accuracy is regained.

2. We studied whether the trajectory and endpoint adaptation achieved with one arm would transfer to the other arm that was never voluntarily moved during rotation. We found virtually complete transfer of endpoint adaptation without transfer of trajectory (path) adaptation.

3. These observations mean that implementation of posture and movement are independent processes. Endpoint control may occur at a relatively central stage that represents general constraints such as gravitoinertial force background or ego-centric direction relevant to both arms, and control of path may occur at a more peripheral stage that represents moments of inertia and muscle dynamics unique to each limb.

4. Endpoint and path adaptation occur without sight of the arm, without tactile cues about the perturbing force, and without visual or tactile cues about where the movements end relative to the target. This implicates muscle spindle signals, efferent monitoring and possibly joint and tendon receptors in a detailed trajectory-monitoring process. Muscle spindle primary and secondary afferent signals may differentially influence adaptation of movement endpoint and shape, respectively.

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