Efeitos do nível de estabilização do desempenho e estruturação da prática na adaptação a pertubações visuais imprevisíveis

Abstract

The motor adaptation to unpredictable perturbations depends on internal models’ capacity to actualize the ongoing motor command through the control mechanism via feedback. The type of practice influences the characteristics of the formed internal models’ and, consequently, motor adaptation, which is better when expert models are formed and specialized to a specific action. The practice beyond performance stabilization and also random practice improves the competence to adapt of the formed internal models. However, no studies investigating the interaction between the level of performance stabilization and practice schedule on adaptation to unpredictable visual perturbation was found. The aim of this thesis was to investigate the interaction effects of the level of performance stabilization and practice schedule on adaptation to unpredictable visual perturbation. Two experiments were run, both composed by two phases: Pre-exposure and Exposure. On experiment I, during Pre-exposure the participants were divided in four groups combining the level of stabilization and practice schedule variables: stabilization-random, stabilization-constant, specialization-random, specialization-constant. On experiment II, the participant reached the performance specialization, but they were divided in two groups of combined practice: random-constant and constant-random. The task consisted of intercept a virtual moving target using an effector. During both experiments, the level of performance stabilization the level of performance stabilization was manipulated with specific criterion of performance. The practice schedule was manipulated through the velocity of target displacement. Twenty-four hours after Preexposure phase started the Exposure phase, when all the groups performed 129 trials, with 99 control trials and 30 perturbation trials. The perturbations were inserted in a unpredictable way and consisted of changing the velocity of target displacement after the onset of the action. The modification was characterized by the velocity increment or decrement when compared to control trials. Summarizing, the results of both experiments showed that performance of all groups increased throughout Pre-exposure phase, and the control predominant mechanism via feedback. The exposure phase tested the competence of the internal models formed during the first phase, when was necessary facing perturbations. In general, the results from experiment I showed that the stabilization-random group was the one which more difficulty to deal with the perturbations, and all the other groups had similar competence. The results from experiment II showed that the group random-constant had more difficulty to deal with perturbations, compared to constant-random group. On both experiments, all groups used predominantly the mechanism control via feedback. These differences point to the interaction effects between the manipulated variables on the internal models competence to adapt to unpredictable visual perturbations.