Himmelbach Marc, Erb Michael, Karnath Hans-Otto
Section Neuropsychology, Center of Neurology, Hertie-Institute for Clinical Brain Research, University of Tübingen, Hoppe-Seyler-Str. 3, D-72076 Tübingen, Germany.
Neuroimage. 2006 Oct 1;32(4):1747-59. doi: 10.1016/j.neuroimage.2006.04.221. Epub 2006 Jun 27.
Inspecting the visual environment, humans typically direct their attention across space by means of voluntary saccadic eye movements. Neuroimaging studies in healthy subjects have identified the superior parietal cortex and intraparietal sulcus as important structures involved in visual search. However, in apparent contrast, spatial disturbance of free exploration typically is observed after damage of brain structures located far more ventrally. Lesion studies in such patients disclosed the inferior parietal lobule (IPL) and temporo-parietal junction (TPJ), the superior temporal gyrus (STG) and insula, as well as the inferior frontal gyrus (IFG) of the right hemisphere. Here we used functional magnetic resonance imaging to investigate the involvement of these areas in active visual exploration in the intact brain. We conducted a region of interest analysis comparing free visual exploration of a dense stimulus array with the execution of stepwise horizontal and vertical saccades. The comparison of BOLD responses revealed significant signal increases during exploration in TPJ, STG, and IFG. This result calls for a reappraisal of the previous thinking on the function of these areas in visual search processes. In agreement with lesion studies, the data suggest that these areas are part of the network involved in human spatial orienting and exploration. The IPL dorsally of TPJ seem to be of minor importance for free visual exploration as these areas appear to be equally involved in the execution of spatially predetermined saccades.
在检查视觉环境时，人类通常通过自主的扫视眼动在空间中引导注意力。对健康受试者的神经影像学研究已确定顶上叶皮质和顶内沟是参与视觉搜索的重要结构。然而，明显的对比是，自由探索的空间干扰通常在位于更腹侧的脑结构受损后才会观察到。对此类患者的病变研究揭示了右半球的顶下小叶（IPL）和颞顶交界区（TPJ）、颞上回（STG）和脑岛，以及额下回（IFG）。在这里，我们使用功能磁共振成像来研究这些区域在完整大脑的主动视觉探索中的参与情况。我们进行了一项感兴趣区域分析，将对密集刺激阵列的自由视觉探索与逐步水平和垂直扫视的执行进行比较。对血氧水平依赖（BOLD）反应的比较显示，在探索过程中，TPJ、STG和IFG有显著的信号增加。这一结果要求重新评估此前对这些区域在视觉搜索过程中功能的认识。与病变研究一致，数据表明这些区域是参与人类空间定向和探索的网络的一部分。TPJ背侧的IPL对自由视觉探索似乎不太重要，因为这些区域在执行空间预定的扫视时似乎同样参与其中。
