A Novel Protocol for the Evaluation of Motor Learning in 3D Reching Tasks Using Novint Falcon

Motor learning or motor adaptation is the capability to acquire new motor skills or the adaptation of existing motor skills to new environmental conditions. In this paper, a new protocol based on a low-cost haptic device for evaluating the motor adaptation during perturbed 3D reaching tasks was presented. The protocol consisted of three 3D reaching tasks performed using Novint Falcon: a familiarization task in which no force field was applied, an adaptation task in which a perturbing force field occurred, and a wash out task with no force field. Ten healthy subjects were enrolled in the study. Subjects were asked to reach four targets equally distributed along a circumference. During the adaptation task, a constant force perpendicular to the direction of movement was applied and it was randomly removed 40 times out of 160. Trajectories of the end-effector were recorded to calculate the following kinematic indices: duration of movement, length ratio, lateral deviation, speed metric and normalized jerk. The learning index was calculated to study the motor learning during the adaptation task. Two-way repeated measure ANOVA tests were performed for all the indices considering movement directions and tasks as independent variables. Moreover, a one-way repeated measure ANOVA was performed on the learning index to find differences among the 4 target sets. The movement accuracy is influenced from both the perturbed force field and the movement direction. The smoothness of the reaching movement is influenced by the presence of the force field and decreases when it is applied. Learning index showed the capability of the subjects to rapidly adapt to a perturbed force field, generating a compensation strategy in a 3D movement.