Sartori Luisa, Camperio-Ciani Andrea, Bulgheroni Maria, Castiello Umberto
Dipartimento di Psicologia Generale, University of Padova, Padova, Italy; Cognitive Neuroscience Center, University of Padova, Padova, Italy.
Dipartimento FISSPA, University of Padova, Padova, Italy.
PLoS One. 2015 Jul 15;10(7):e0132937. doi: 10.1371/journal.pone.0132937. eCollection 2015.
The most popular model to explain how prehensile movements are organized assumes that they comprise two "components", the reaching component encoding information regarding the object's spatial location and the grasping component encoding information on the object's intrinsic properties such as size and shape. Comparative kinematic studies on grasping behavior in the humans and in macaques have been carried out to investigate the similarities and differences existing across the two species. Although these studies seem to favor the hypothesis that macaques and humans share a number of kinematic features it remains unclear how the reaching and grasping components are coordinated during prehension movements in free-ranging macaque monkeys. Twelve hours of video footage was filmed of the monkeys as they snatched food items from one another (i.e., snatching) or collect them in the absence of competitors (i.e., unconstrained). The video samples were analyzed frame-by-frame using digitization techniques developed to perform two-dimensional post-hoc kinematic analyses of the two types of actions. The results indicate that only for the snatching condition when the reaching variability increased there was an increase in the amplitude of maximum grip aperture. Besides, the start of a break-point along the deceleration phase of the velocity profile correlated with the time at which maximum grip aperture occurred. These findings suggest that macaques can spatially and temporally couple the reaching and the grasping components when there is pressure to act quickly. They offer a substantial contribution to the debate about the nature of how prehensile actions are programmed.
用来解释抓握动作如何组织的最流行模型假定，抓握动作由两个“成分”组成，即“伸手”成分，它编码有关物体空间位置的信息；以及“抓握”成分，它编码有关物体固有属性（如大小和形状）的信息。为了研究人类和猕猴抓握行为的异同，已经开展了比较运动学研究。尽管这些研究似乎支持猕猴和人类具有一些运动学特征的假说，但目前仍不清楚在自由活动的猕猴进行抓握动作时，伸手和抓握成分是如何协调的。研究人员拍摄了12小时的视频片段，记录猕猴相互抢夺食物（即抢夺行为）或在没有竞争者的情况下收集食物（即无约束行为）的过程。利用为对这两种动作进行二维事后运动学分析而开发的数字化技术，逐帧分析视频样本。结果表明，只有在伸手动作变异性增加的抢夺条件下，最大抓握孔径的幅度才会增加。此外，沿着速度曲线减速阶段的一个断点的开始与最大抓握孔径出现的时间相关。这些发现表明，当有快速行动的压力时，猕猴能够在空间和时间上协调伸手和抓握成分。它们为有关抓握动作如何编程的本质的争论做出了重大贡献。
