Gangitano M, Daprati E, Gentilucci M
Institute of Human Physiology, University of Parma, Italy.
Exp Brain Res. 1998 Oct;122(4):441-52. doi: 10.1007/s002210050532.
In the present study we addressed the issue of how an object is visually isolated from surrounding cues when a reaching-grasping (prehension) movement towards it is planned. Subjects were required to reach and grasp an object presented either alone or with a distractor. In five experiments, different degrees of elaboration of the distractor were induced by varying: (1) the position of the distractor (central or peripheral); (2) the time when the distractor was suppressed (immediately or delayed, with respect to stimulus presentation); and (3) the type of distractor analysis (implicit or explicit). In addition, we tested whether the possible effects of the distractor on reaching-grasping were due to the use of an allocentric reference centered on it. This was obtained by comparing the effects of the distractor with those of a stimulus, the target of a placing movement successive to the reaching-grasping. The results of the five experiments can be summarized as follows. The necessary condition for an interference effect on both the reaching and the grasping components was the central presentation of the distractor. When the information on the distractor could be immediately suppressed, an interference effect was observed only on the grasp component. In the case of delayed suppression, an effect was found on the reaching component. Finally, when an overt analysis of the distractor was required, the interference effect disappeared. Two main conclusions have been drawn from the results of the present study. First, comparison between properties of the target and surrounding cues is performed by two independent processes for reaching and grasping an object. The process for the grasp relies more on allocentric cues than that for the reach. Second, when surrounding stimuli are automatically analyzed during visual search of the target, the process of visuo-motor transformation can incorporate their features into the target. In contrast, overt analysis of surrounding stimuli is performed separately from that of the target. Finally, the data of the present study are discussed in support of the premotor theory of attention.
在本研究中，我们探讨了在计划向一个物体进行伸手抓握（prehensile）动作时，该物体是如何从周围线索中被视觉孤立出来的问题。要求受试者伸手抓握单独呈现或伴有干扰物的物体。在五个实验中，通过改变以下因素诱导出不同程度的干扰物精细化：（1）干扰物的位置（中央或周边）；（2）干扰物被抑制的时间（相对于刺激呈现立即或延迟）；（3）干扰物分析的类型（内隐或外显）。此外，我们测试了干扰物对伸手抓握可能产生的影响是否归因于以其为中心的异心参考系的使用。这是通过比较干扰物与一个刺激（伸手抓握之后放置动作的目标）的影响来实现的。五个实验的结果可总结如下。对伸手和抓握成分产生干扰效应的必要条件是干扰物的中央呈现。当干扰物的信息能够立即被抑制时，仅在抓握成分上观察到干扰效应。在延迟抑制的情况下，在伸手成分上发现了效应。最后，当需要对干扰物进行公开分析时，干扰效应消失。从本研究的结果中得出了两个主要结论。首先，对于伸手抓握一个物体，目标属性与周围线索之间的比较是由两个独立的过程进行的。抓握过程比伸手过程更依赖于异心线索。其次，当在对目标进行视觉搜索期间自动分析周围刺激时，视运动转换过程可以将其特征纳入目标。相反，对周围刺激的公开分析与对目标的分析是分开进行的。最后，讨论了本研究的数据以支持注意的运动前理论。
