Department of Psychology, University of Windsor, 401 Sunset Avenue, Windsor, ON, Canada N9B 3P4.
Brain Cogn. 2011 Aug;76(3):341-8. doi: 10.1016/j.bandc.2011.04.008. Epub 2011 May 19.
The superior parietal cortex is critical for the control of visually guided actions. Research suggests that visual stimuli relevant to actions are preferentially processed when they are in peripersonal space. One recent study demonstrated that visually guided movements towards the body were more impaired in a patient with damage to superior parietal cortex. Whereas past studies have explored disordered movement in optic ataxic patients, there has been less exploration of space perception in terms of search capacity in this population. In addition, there is some debate concerning the relationship between deficits of visuomotor control and impaired attention/perception in optic ataxia. Given that the dorsal stream has been implicated in the spatial processing of stimuli in peripersonal space, and damage to this region is known to cause optic ataxia, we felt that further investigation was warranted. We examined tactile search behavior in the fronto-parallel and radial planes in a patient with right superior parietal damage and optic ataxia. We used a pegboard with removable cylindrical pegs that allowed for the reorganization of targets between trials. To better characterize three-dimensional search behavior, we included both horizontal and vertical search conditions. Results showed that the patient spent more time searching, was more accurate and revisited more targets in right versus left space. Interestingly, the patient spent the majority of her time specifically searching the lower right quadrant of the stimulus array. Further analysis revealed lower target detection rates along the outer borders of the pegboard on all sides. The search pattern observed here is unusual considering that all targets were within arm's reach. The present experiment demonstrates that damage to superior parietal cortex impairs tactile search and biases exploration towards lower right peripersonal space.
顶叶上皮质对视觉引导动作的控制至关重要。研究表明，与动作相关的视觉刺激在处于近体空间时会被优先处理。最近的一项研究表明，当顶叶上皮质受损时，朝向身体的视觉引导运动受到的影响更大。虽然过去的研究已经探索了视动性共济失调患者的运动障碍，但在该人群中，对搜索能力的空间感知的研究较少。此外，关于视动控制缺陷与视动性共济失调中注意力/感知障碍之间的关系存在一些争议。鉴于背侧流在近体空间中对刺激的空间处理起作用，并且该区域的损伤已知会导致视动性共济失调，我们认为有必要进一步研究。我们检查了一名右顶叶损伤伴视动性共济失调患者在前平行和放射状平面上的触觉搜索行为。我们使用带有可移动圆柱销的钉板，允许在试验之间重新组织目标。为了更好地描述三维搜索行为，我们包括了水平和垂直搜索条件。结果表明，患者在右侧空间的搜索时间更长、更准确、并重新访问更多目标。有趣的是，患者将大部分时间专门用于搜索刺激数组的右下象限。进一步的分析显示，在钉板的所有边缘外侧，目标检测率较低。考虑到所有目标都在手臂可及范围内，这里观察到的搜索模式是不寻常的。本实验表明，顶叶上皮质损伤会损害触觉搜索，并使探索偏向右下近体空间。
