Brouwer Anne-Marie, Knill David C
Center for Visual Science, University of Rochester, Rochester, NY, USA.
J Vis. 2007 Jun 22;7(5):6.1-12. doi: 10.1167/7.5.6.
People can be shown to use memorized location information to move their hand to a target location if no visual information is available. However, for several reasons, memorized information may be imprecise and inaccurate. Here, we study whether and to what extent humans use the remembered location of an object to plan reaching movements when the target is visible. Subjects sequentially picked up and moved two different virtual, "magnetic" target objects from a target region into a virtual trash bin with their index fingers. In one third of the trials, we perturbed the position of the second target by 1 cm while the finger was transporting the first target to the trash. Subjects never noticed this. Although the second target was visible in the periphery, subjects' movements were biased to its initial (remembered) position. The first part of subjects' movements was predictable from a weighted sum of the visible and remembered target positions. For high contrast targets, subjects initially weigh visual and remembered information about target position in an average ratio of 0.67 to 0.33. Over the course of the movement, weight given to memory decreased. Diminishing the contrast of the targets substantially increased the weight that subjects gave to the remembered location. Thus, even when peripheral visual information is available, humans use the remembered location of an object to plan goal-directed movements. In contrast to previous suggestions in the literature, our results indicate that absolute location is remembered quite well.
如果没有视觉信息，人们可以利用记忆中的位置信息将手移动到目标位置。然而，由于多种原因，记忆信息可能不精确且不准确。在此，我们研究当目标可见时，人类是否以及在多大程度上利用物体的记忆位置来计划伸手动作。受试者用食指依次从目标区域拿起并移动两个不同的虚拟“磁性”目标物体到一个虚拟垃圾桶中。在三分之一的试验中，当手指将第一个目标物体运送到垃圾桶时，我们将第二个目标物体的位置扰动1厘米。受试者从未注意到这一点。尽管第二个目标物体在周边可见，但受试者的动作仍偏向其初始（记忆中的）位置。受试者动作的第一部分可以通过可见目标位置和记忆目标位置的加权和来预测。对于高对比度目标，受试者最初对目标位置的视觉信息和记忆信息的加权平均比例为0.67比0.33。在动作过程中，赋予记忆的权重降低。降低目标物体的对比度会大幅增加受试者赋予记忆位置的权重。因此，即使周边有视觉信息，人类仍会利用物体的记忆位置来计划目标导向的动作。与文献中先前的观点相反，我们的结果表明绝对位置被很好地记住了。
