Marotta J J, Goodale M A
Department of Psychology, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
J Cogn Neurosci. 2001 Jan 1;13(1):8-17. doi: 10.1162/089892901564135.
The present study examined whether the learned pictorial depth cue of "familiar size" could be used to plan a reaching and grasping movement in the absence of binocular vision. Sixteen right-handed subjects were presented with two different arrays, under monocular and binocular viewing conditions, in which a range of different "grasp-sized" spheres that were lit from within could be presented in an otherwise darkened environment. In the "familiar-size" presentation array, only one "standard" sized sphere was presented, which gave subjects an opportunity to learn the relationship between the standard sphere's retinal image size and its distance. In the "multiple" spheres presentation array, subjects could not learn such a relationship because on any one trial, one of four different sphere sizes could be present. In a second experiment, the effects of this paradigm on six subjects' perceptual reports of distance were examined by having subjects slide their index fingers apart along a horizontal rod to indicate the estimated distance of the spheres. When familiar size could not be used as a cue to distance, subjects produced more on-line corrections in their reaching and grasping movements to the standard-sized spheres--but only under monocular viewing conditions. It appears that subjects are able to exploit the learned relationship between an object's distance and its projected retinal image size to help program and control reaching and grasping movements when binocular vision is not available. Although the influence of familiar size on subjects' perceptual estimates is less clear, it is clear that subjects' perceptual estimates show poor absolute scaling for distance. This result further supports the notion that under normal viewing conditions the visuomotor system uses binocular information to program and control manual prehension, but is able to use pictorial information when binocular vision is denied.
本研究考察了在没有双眼视觉的情况下，习得的“熟悉大小”这一图形深度线索是否可用于规划伸手抓取动作。16名右利手受试者在单眼和双眼观察条件下，面对两种不同的阵列，在其他方面均为黑暗的环境中呈现一系列从内部发光的不同“抓取大小”的球体。在“熟悉大小”呈现阵列中，仅呈现一个“标准”大小的球体，这使受试者有机会了解标准球体视网膜图像大小与其距离之间的关系。在“多个”球体呈现阵列中，受试者无法了解这种关系，因为在任何一次试验中，可能出现四种不同球体大小中的一种。在第二个实验中，通过让受试者沿水平杆将食指分开以指示球体的估计距离，考察了该范式对6名受试者距离感知报告的影响。当熟悉大小不能用作距离线索时，受试者在伸手抓取标准大小球体的动作中会进行更多的在线校正——但仅在单眼观察条件下。似乎受试者能够利用习得的物体距离与其视网膜投影图像大小之间的关系，在没有双眼视觉时帮助规划和控制伸手抓取动作。尽管熟悉大小对受试者感知估计的影响不太明确，但很明显受试者的感知估计在距离的绝对标度方面表现不佳。这一结果进一步支持了这样一种观点，即在正常观察条件下，视觉运动系统利用双眼信息来规划和控制手动抓握，但在双眼视觉缺失时能够利用图形信息。
