Visuospatial processing deficits are typically associated with damage to the right hemisphere. However, deficits on spatial working memory have been reported among some individuals with focal left hemisphere damage (LHD). It has been suggested that the left hemisphere may play a role in such non-verbal working memory tasks due to the use of subvocal, verbally-mediated strategies. The current study investigated the role of the left hemisphere in spatial working memory by testing spatial span performance, both forward and backward, in a large group of individuals with a history of left hemisphere stroke. Our first aim was to establish whether individuals with LHD are indeed impaired on spatial span tasks using standardized span tasks with published normative data. Our second aim was to identify the role that language plays in supporting spatial working memory by comparing LHD individuals with and without aphasia, and by relating spatial span performance to performance on a series of language measures. Our third aim was to identify left hemisphere brain regions that contribute to spatial working memory using voxel-based lesion symptom mapping (VLSM), a whole-brain statistical approach that identifies regions critical to a particular behavior on a voxel-by-voxel basis. We found that 28% of individuals with LHD performed in the clinically-impaired range on forward spatial span and 16% performed in the clinically-impaired range on backward spatial span. There were no significant differences in performance between individuals with and without aphasia, and there were no correlations between spatial span performance and language functions such as repetition and comprehension. The VLSM analysis showed that backward spatial span was associated with a left fronto-parietal network consisting of somatosensory cortex, the supramarginal gyrus, lateral prefrontal cortex, and the frontal eye fields. Regions identified in the VLSM analysis of forward spatial span did not reach the conservative statistical threshold for significance. Overall, these results suggest that spatial working memory, as measured by spatial span, can be significantly disrupted in a subset of individuals with LHD whose lesions infringe on a network of regions in the left hemisphere that have been implicated in domain-general working memory and attentional control mechanisms.

中文翻译：

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左半球在视觉空间工作记忆中的作用

视觉空间处理缺陷通常与右半球损伤有关。然而，据报道，一些患有局灶性左半球损伤 (LHD) 的个体存在空间工作记忆缺陷。有人提出，由于使用了隐含的、语言介导的策略，左半球可能在此类非语言工作记忆任务中发挥作用。目前的研究通过在一大群有左半球中风病史的个体中测试空间跨度表现（向前和向后）来调查左半球在空间工作记忆中的作用。我们的第一个目标是使用标准化的跨度任务和已发布的规范数据来确定 LHD 个体是否确实在空间跨度任务上受损。我们的第二个目标是通过比较有和没有失语症的 LHD 个体，并将空间跨度表现与一系列语言测量的表现联系起来，确定语言在支持空间工作记忆中的作用。我们的第三个目标是使用基于体素的病变症状映射 (VLSM) 来识别对空间工作记忆有贡献的左半球大脑区域，VLSM 是一种全脑统计方法，可在逐个体素的基础上识别对特定行为至关重要的区域。我们发现 28% 的 LHD 个体在前向空间跨度的临床受损范围内进行，16% 在后向空间跨度上的临床受损范围内进行。失语症患者和非失语症患者的表现没有显着差异，空间跨度表现与语言功能如重复和理解之间没有相关性。VLSM 分析表明，后向空间跨度与由躯体感觉皮层、缘上回、外侧前额叶皮层和额叶眼区组成的左额顶叶网络相关。在前向空间跨度的 VLSM 分析中确定的区域未达到显着性的保守统计阈值。总体而言，这些结果表明，空间工作记忆（以空间跨度衡量）在一部分 LHD 个体中可能受到显着破坏，这些个体的病变侵犯了左半球区域网络，这些区域与域一般工作记忆和注意力控制机制。