Trommershäuser Julia, Gepshtein Sergei, Maloney Laurence T, Landy Michael S, Banks Martin S
Department of Psychology, Giessen University, 35394 Giessen, Germany.
J Neurosci. 2005 Aug 3;25(31):7169-78. doi: 10.1523/JNEUROSCI.1906-05.2005.
Effective movement planning should take into account the consequences of possible errors in executing a planned movement. These errors can result from either sensory uncertainty or variability in movement planning and production. We examined the ability of humans to compensate for variability in sensory estimation and movement production under conditions in which variability is increased artificially by the experimenter. Subjects rapidly pointed at a target region that had an adjacent penalty region. Target and penalty hits yielded monetary rewards and losses. We manipulated the task-relevant variability by perturbing visual feedback of finger position during the movement. The feedback was shifted in a random direction with a random amplitude in each trial, causing an increase in the task-relevant variability. Subjects were unable to counteract this form of perturbation. Rewards and penalties were based on the perturbed, visually specified finger position. Subjects rapidly acquired an estimate of their new variability in <120 trials and adjusted their aim points accordingly. We compared subjects' performance to the performance of an optimal movement planner maximizing expected gain. Their performance was consistent with that expected from an optimal movement planner that perfectly compensated for externally imposed changes in task-relevant variability. When exposed to novel stimulus configurations, aim points shifted in the first trial without showing any detectable trend across trials. These results indicate that subjects are capable of changing their pointing strategy in the presence of externally imposed noise. Furthermore, they manage to update their estimate of task-relevant variability and to transfer this estimate to novel stimulus configurations.
有效的运动规划应考虑到执行计划运动时可能出现的错误所带来的后果。这些错误可能源于感官不确定性或运动规划与产生过程中的变异性。我们研究了在实验者人为增加变异性的条件下，人类补偿感官估计和运动产生变异性的能力。受试者迅速指向一个有相邻惩罚区域的目标区域。命中目标和惩罚区域会带来金钱奖励和损失。我们通过在运动过程中干扰手指位置的视觉反馈来操纵与任务相关的变异性。在每次试验中，反馈会在随机方向上以随机幅度移动，从而导致与任务相关的变异性增加。受试者无法抵消这种形式的干扰。奖励和惩罚基于受干扰的、视觉上指定的手指位置。受试者在不到120次试验中迅速获得了对其新变异性的估计，并相应地调整了他们的目标点。我们将受试者的表现与最大化预期收益的最优运动规划器的表现进行了比较。他们的表现与最优运动规划器预期的表现一致，该规划器能完美补偿与任务相关的变异性的外部强加变化。当暴露于新的刺激配置时，目标点在第一次试验中就发生了移动，且在各次试验中未显示出任何可检测到的趋势。这些结果表明，受试者能够在存在外部强加噪声的情况下改变他们的指向策略。此外，他们设法更新对与任务相关的变异性的估计，并将这一估计应用于新的刺激配置。
