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Obstacle Perseveration Effect on Manual Pointing Trajectories

The aim of this study was to determine whether previous trajectory plans reused in aiming targets with obstacles sometimes emerge in the way. For this purpose, in two experiments, right hand position of voluntary male students (N=55, 18-22 years) was measured in conditions that presence of obstacle in sequential trails was changed (randomly, in first experiment; predictable sequences in second experiment) by using potentiometer encoders located at the manipulandum joints. In first experiment, ANOVA results showed that trajectories when no obstacles were present had more start angel (motor planning index) if obstacle had recently appeared than if obstacles had not recently appeared (p<0.001). In the second experiment, from the similarity (F<1) between start angel of groups (predictable sequence groups with and without instruction; random pattern group) concluded that not only trajectory perseveration effect was not the result of sequential expectancy, but also this effect was related to trajectory planning. In general, we inferenced that control of sequential obstacle avoidance movements depended on previous movements and that in the motor planning, optimization of computational costs of trajectory formation preferred by minimal biomechanical costs of effectors.