Dijkerman H C, Milner A D, Carey D P
School of Psychology, University of St. Andrews, Fife, Scotland, UK.
Exp Brain Res. 1996 Dec;112(3):442-51. doi: 10.1007/BF00227950.
Previous studies have reported that the visual form agnosic D.F. is able to use information about visual targets for the control of motor acts, but has great difficulty in using the same visual information for perceptual report. This intact visuomotor performance may be mediated by relatively intact parieto-frontal cortical mechanisms. The present study investigated the ability of D.F. to use binocular and monocular information about the orientation of an object in the depth plane for perceptual and visuomotor purposes. A square plaque was presented at seven different orientations in depth to D.F. and to three age- and sex-matched control subjects. Subjects were required to reach out and grasp the plaque using a precision grip (index finger and thumb) under binocular and monocular viewing conditions, and in separate trials to match the orientation of a hand-held plaque to the perceived orientation of the target object, also under both binocular and monocular conditions. D.F.'s performance in grasping trials was found to be normal under binocular conditions, but was substantially worsened by removal of binocular vision. She was severely impaired at matching the orientation of the test square, although under binocular conditions her performance rose clearly above chance. The data suggest that the separation of cortical processing for visuomotor and visual perceptual purposes also applies, at least in part, to information about the orientation in depth of an object. The impaired performance under monocular viewing conditions on the visuomotor task is in agreement with recent physiological data and suggests that posterior parietal systems depend critically on binocular input for the processing of orientation in depth when ventral-stream information is unavailable.
以往的研究报告称，患有视觉形式失认症的D.F.能够利用有关视觉目标的信息来控制运动行为，但在将相同的视觉信息用于感知报告时却有很大困难。这种完好无损的视觉运动表现可能由相对完好的顶叶 - 额叶皮质机制介导。本研究调查了D.F.利用关于物体在深度平面上的方向的双眼和单眼信息进行感知和视觉运动的能力。向D.F.以及三名年龄和性别匹配的对照受试者在深度上以七个不同方向呈现一个方形板。受试者被要求在双眼和单眼观察条件下伸出手并用精确抓握（食指和拇指）抓住板，并在单独的试验中在双眼和单眼条件下将手持板的方向与目标物体的感知方向相匹配。发现在双眼条件下，D.F.在抓握试验中的表现正常，但去除双眼视觉后表现大幅恶化。尽管在双眼条件下她的表现明显高于随机水平，但她在匹配测试方块的方向时严重受损。数据表明，用于视觉运动和视觉感知目的的皮质处理分离至少部分也适用于关于物体深度方向的信息。在单眼观察条件下视觉运动任务的受损表现与最近的生理学数据一致，并表明当腹侧流信息不可用时，后顶叶系统在处理深度方向时严重依赖双眼输入。
