Discrete and continuous planning of hand movements and isometric force trajectories

摘要: We have previously demonstrated that, in preparing themselves to aim voluntary impulses of isometric elbow force unpredictable targets, subjects selected default values for amplitude and direction according the range targets that they expected. Once a specific target appeared, specified through parallel processes. Amplitude was continuously from an average or central default; stochastically one directions. Using same timed response paradigm, we now report three experiments examine how time available processing information influences trajectory characteristics two-degree-of-freedom forces multijoint movements. first sought determine whether specification could also take form discrete stochastic process pulses wrist muscle force, where can vary continuously. With four equiprobable (two amplitudes each two directions separated by 22° 90°), value both narrow wide separations as continuous variable. Direction, however, remained variable separations. For separations, directional distribution responses suggested presence values. next examined point-to-point movements planar hand movement task with at distances but five (from 30° 150° separation). found extent again default. Direction discretely alternative when separation narrow. The evolved over 200-ms period beginning about 100 ms after presentation. As pulses, progressively correct wrong progressive improvement scaling acceleration velocity peaks target. On other hand, path straightness did not change significantly course specification. Thus, linearity, global features trajectories, are given priority direction. In third experiment, varied between unidirectional pairs is discretely, like direction, disparity large. implications these findings contextual effects on planning discussed. independence prior setting duration provide critical support hypothesis planned vectorially.