Martin Jason A, Karnath Hans-Otto, Himmelbach Marc
Division of Neuropsychology, Center of Neurology, Hertie-Institute for Clinical Brain Research, Eberhard Karls University, Tübingen, Germany.
Division of Neuropsychology, Center of Neurology, Hertie-Institute for Clinical Brain Research, Eberhard Karls University, Tübingen, Germany.
Cortex. 2015 Mar;64:363-79. doi: 10.1016/j.cortex.2014.11.012. Epub 2014 Dec 16.
Optic ataxia (OA) is a neurological disorder that is characterised by misreaching to targets in the visual periphery. The anatomy of OA thus provides important information for the neural representation of visually guided reaching in humans. In 2005 a lesion mapping analysis of OA localised the critical lesion site at the parieto-occipital junction (POJ) (Karnath & Perenin, 2005). This work was accompanied by the discovery of a peripheral reaching module at the POJ in an fMRI study (Prado et al., 2005). The ostensible overlap between the territory typically affected in patients with OA and the findings of Prado et al. (2005) had a tremendous influence on the search for a cortical peripheral reaching module. However, a close inspection of the functional Magnetic Resonance Imaging (fMRI) study revealed that a comparison between reaching towards visible targets in the peripheral visual field and reaching to visible targets in the central visual field--which is the key aspect in clinical examinations of OA--was not conducted. Moreover, whereas main effects of reaching overlapped with the OA lesion site, specific interaction effects did not overlap. We performed a direct comparison between reaching to visible peripheral targets and reaching to visible central targets to address the inconsistencies between the aforementioned studies. Our analysis shows that Prado et al.'s study cannot be taken as evidence for a delineated module for peripheral reaching. In contrast to Prado et al. we found a combined system of POJ, IPS and SPL areas--the posterior human 7A, mIPS, V6A and the posterior IPS--with increased signals during reaching to peripheral targets.
视觉性共济失调（OA）是一种神经障碍，其特征是在视觉外周区域向目标伸手时出现误抓。因此，OA的解剖结构为人类视觉引导伸手的神经表征提供了重要信息。2005年，一项对OA的病灶定位分析将关键病灶部位定位于顶枕交界处（POJ）（卡尔纳特和佩雷宁，2005年）。这项工作伴随着在一项功能磁共振成像（fMRI）研究中发现POJ处存在一个外周伸手模块（普拉多等人，2005年）。OA患者通常受影响区域与普拉多等人（2005年）研究结果之间表面上的重叠，对寻找皮质外周伸手模块产生了巨大影响。然而，仔细检查该功能磁共振成像研究发现，并未对外周视野中向可见目标伸手与中央视野中向可见目标伸手进行比较——而这是OA临床检查的关键方面。此外，虽然伸手的主效应与OA病灶部位重叠，但特定的交互效应并不重叠。我们对向可见外周目标伸手和向可见中央目标伸手进行了直接比较，以解决上述研究之间的不一致之处。我们的分析表明，普拉多等人的研究不能作为存在一个明确的外周伸手模块的证据。与普拉多等人不同，我们发现POJ、顶内沟（IPS）和顶上小叶（SPL）区域——即后人类7A区、内侧IPS、V6A区和后IPS区——在向外周目标伸手时信号增强，形成了一个联合系统。
