Efeitos da organização da prática variada sobre a adaptação motora a perturbações previsíveis e imprevisíveis

Abstract

Environmental changes may impose new sensorimotor demands, which challenge motor performance. These changes, or perturbations, may be predictable, enabling previous preparation and organization of action, or unpredictable, enabling organization of action only after its presentation. Despite the kind of perturbation, maintenance of good performance requires an adaptable motor response, which is related to previous practice, noteworthy its variability: higher variability of practice appears to lead to better adaptation. However, the effects of the scheduling of such variations in a practice session upon motor adaptation are yet unknown, despite its influence on the detection of environmental and task changes, and on action planning according to these changes. Thus, the main purpose of this study was to investigate the effects of variable practice scheduling, blocked and random, on motor behavior in contexts under predictable, and in contexts under unpredictable perturbations. Two experiments were carried out, and in both of them there was a group under blocked practice and a group under random practice that practiced three variations (i.e. speed) of a coincident timing task according to the specified group. Task consisted of touching five photoelectrical sensors in sequence and finishing the sequence in coincidence to a light stimulus fully visible. After an interval of 24h, subjects practiced under perturbations (i.e. speed changes in light stimulus) common to both groups. In the first experiment perturbations were made predictable and in the second experiment they were unpredictable. Analyses were carried on performance and action organization, and results showed that both practice schedules enable adaptation to predictable perturbation, but random practice enabled better performance under unpredictable perturbations. In both perturbation conditions, groups presented differences in action organization. These results were credited to the development of different ability to extract and use information about velocity differences between light stimuli inaction organization during practice in each schedule. According to the Multiple paired inverse-forward models theory, applied to combine the results of both experiments, random practice enables the formation of more competent control modules (i.e. sensorimotor maps) with control elements more efficient at producing motor commands, as well as more efficient responsibility predictors able to identifying environmental conditions and specifying modules contribution to the actual condition. These predictors were formed and calibrated during practice through the frequent changes in task conditions. Blocked practice, on the other hand, enables the formation of control elements but restrains the formation of predictor of responsibility due to consecutive repetitions of same task demand, which results in a increased difficulty in detecting changes and, consequently, in a poorer performance under unpredictable perturbations.