Energy margins in dynamic object manipulation
Energy margins in dynamic object manipulation
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DOI：
10.1152/jn.00019.2012
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发表时间：
2012-09-01
影响因子：
2.5
通讯作者：
Sternad, Dagmar
中科院分区：
文献类型：
--
作者：
Hasson, Christopher J.;Shen, Tian;Sternad, Dagmar
放大图片作者：J.动态对象操作中的能量裕度。J Neurophysiol 108：1349 - 1365，2012.首次发表于2012年5月16日; doi：10.1152/jn.00019.2012. -许多任务需要人类动态地操纵复杂的对象并保持适当的安全裕度，例如将一杯咖啡放在杯垫上而不溢出。这项研究研究探讨了人类如何学习这种安全边际，以及它们是如何通过任务约束和随着技能的提高而变化的可变性来塑造的。18名受试者使用一个机械手巨人将一个装有球的浅虚拟杯子运送到一个目标而不丢失球。一半人在2秒的舒适目标时间内完成杯子运输（具有无限多等效解决方案的冗余任务），另一半人在最短时间内完成（具有一个明确成本的非冗余任务）。安全裕度被定义为相对于逃逸的球能量，即，作为一种能量边际。第一个假设，即受试者收敛到一个单一的策略，在最短时间的任务，但选择不同的策略，在较少的限制目标时间的任务，不支持。两组人都通过实践发展了个性化的策略。第二个假设，即受试者在最短时间任务中降低安全裕度，但在目标时间任务中增加安全裕度，得到了支持。第三个假设，即在这两个任务受试者调节能源边际根据其执行的变化，部分支持。在目标时间组中，能量边际的变化与执行变异性的变化呈正相关;在最短时间组中，这种关系只在练习结束时观察到，而不是在练习过程中。这些结果表明，当学习一个冗余的对象操作任务，大多数受试者增加他们的安全裕度和形状的运动策略，根据他们不断变化的可变性。
Hasson CJ, Shen T, Sternad D. Energy margins in dynamic object manipulation. J Neurophysiol 108: 1349-1365, 2012. First published May 16, 2012; doi:10.1152/jn.00019.2012.-Many tasks require humans to manipulate dynamically complex objects and maintain appropriate safety margins, such as placing a cup of coffee on a coaster without spilling. This study examined how humans learn such safety margins and how they are shaped by task constraints and changing variability with improved skill. Eighteen subjects used a manipulandum to transport a shallow virtual cup containing a ball to a target without losing the ball. Half were to complete the cup transit in a comfortable target time of 2 s (a redundant task with infinitely many equivalent solutions), and the other half in minimum time (a nonredundant task with one explicit cost to optimize). The safety margin was defined as the ball energy relative to escape, i.e., as an energy margin. The first hypothesis, that subjects converge to a single strategy in the minimum-time task but choose different strategies in the less constrained target-time task, was not supported. Both groups developed individualized strategies with practice. The second hypothesis, that subjects decrease safety margins in the minimum-time task but increase them in the target-time task, was supported. The third hypothesis, that in both tasks subjects modulate energy margins according to their execution variability, was partially supported. In the target-time group, changes in energy margins correlated positively with changes in execution variability; in the minimum-time group, such a relation was observed only at the end of practice, not across practice. These results show that when learning a redundant object manipulation task, most subjects increase their safety margins and shape their movement strategies in accordance with their changing variability.