Optic ataxia as a result of the breakdown of the global tuning fields of parietal neurones
Optic ataxia as a result of the breakdown of the global tuning fields of parietal neurones
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DOI：
10.1093/brain/awf034
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发表时间：
2002-02-01
期刊：
影响因子：
14.5
通讯作者：
Caminiti, R
中科院分区：
文献类型：
--
作者：
Battaglia-Mayer, A;Caminiti, R
视性共济失调的特征是手臂到达视觉目标的方向的视觉控制受损，并伴有手的方向和握力形成缺陷。在人类中，视性共济失调与顶上小叶(SPL)的损害有关，这也会影响视觉引导的眼跳和其他形式的眼手协调。在过去的10年里，对SPL的解剖学和生理学研究揭示了顶叶皮质在控制眼-手联合运动到视觉目标中的作用，以及连接顶叶和额叶皮质的潜在分布网络。SPL神经元的一个新出现的主要功能特征似乎是它们以空间一致的方式组合不同方向的眼睛和手相关信息的能力，到目前为止提出的任何编码方案都认为这些信息对于组成到达的运动命令是必不可少的。这种整合发生在顶神经元的全局调谐领域内，与上下文相关，涉及具有相同方向性的眼睛和手信息。根据任务要求，这种信号集成可以产生不同参考系的表示，以用于协调眼部-手部运动。在全局调谐场内发生的动态操作可以至少部分地依赖于连接SPL和额叶的运动前区域的相互关联连接集。从这张图片中，SPL既是额叶皮质视觉输入的主要来源，也是基于折返信号的视觉运动整合的关键结构，因此，它是视觉运动控制的关键节点。有人假设，在顶叶患者中，表征触觉的定向错误是顶神经元全局调谐区域内定向眼球和手部信息组合崩溃的结果。在这些患者中，目标位置、眼睛和手的位置以及运动方向的信息之间的空间匹配将被阻止，从而损害视觉引导的眼-手运动的组成。这种崩溃可能至少在一定程度上依赖于额顶回信号的失败，这是连接顶叶和额叶皮质的皮质系统退化的明显后果。事实上，皮质-皮质连接对于塑造皮质神经元的动态特性是必不可少的。
Optic ataxia is characterized by an impaired visual control of the direction of arm reaching to a visual target, accompanied by defective hand orientation and grip formation. In humans, optic ataxia is associated with lesions of the superior parietal lobule (SPL), which also affect visually guided saccades and other forms of eye-hand coordination. In the last 10 years, anatomical and physiological studies of the SPL have shed new light on the role of parietal cortex in the control of combined eye-hand movements to visual targets, and on the underlying distributed network which links parietal to frontal cortex. A main emerging functional feature of SPL neurones seems to be their capacity to combine, in a spatially congruent fashion, different directional eye- and hand-related information, that any coding scheme so far proposed, considers essential for the composition of motor commands for reaching. This integration occurs within the global tuning field of parietal neurones, is context-dependent and involves eye and hand information that shares the same directional properties. Depending on task demands, this integration of signals can result in the representation of different reference frames for coordinated eye-hand movements. The dynamic operations occurring within the global tuning fields might depend, at least in part, on the reciprocal sets of association connections linking the SPL and the premotor areas of the frontal lobe. From this picture, the SPL emerges as both a main source of visual input to the frontal cortex and a key structure for visuomotor integration based on re-entrant signalling and, therefore, as a crucial node in the visual control of movement. It is hypothesized that in parietal patients, the directional errors that characterize reaching are a consequence of the breakdown of the combination of directional eye and hand information within the global tuning fields of parietal neurones. In these patients, the spatial match among information about target location, eye and hand position, and movement direction would be prevented, so as to impair the composition of visually guided eye-hand movements. This breakdown could be dependent, at least in part, on the failure of a re-entrant frontoparietal signalling, an obvious consequence of the degeneration of the cortico-cortical systems linking parietal and frontal cortex. Cortico-cortical connections are, in fact, essential for shaping the dynamic properties of cortical neurones.