Department of Neurology and Clinical Neurosciences, University Medical Centre Freiburg, Germany Freiburg Brain Imaging Centre, University of Freiburg, Germany BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Germany
Department of Neurology and Clinical Neurosciences, University Medical Centre Freiburg, Germany Freiburg Brain Imaging Centre, University of Freiburg, Germany BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Germany.
Brain. 2016 May;139(Pt 5):1497-516. doi: 10.1093/brain/aww035. Epub 2016 Mar 8.
Apraxia is a debilitating cognitive motor disorder that frequently occurs after left hemisphere stroke and affects tool-associated and imitative skills. However, the severity of the apraxic deficits varies even across patients with similar lesions. This variability raises the question whether regions outside the left hemisphere network typically associated with cognitive motor tasks in healthy subjects are of additional functional relevance. To investigate this hypothesis, we explored regions where functional magnetic resonance imaging activity is associated with better cognitive motor performance in patients with left hemisphere ischaemic stroke. Thirty-six patients with chronic (>6 months) large left hemisphere infarcts (age ± standard deviation, 60 ± 12 years, 29 male) and 29 control subjects (age ± standard deviation, 72 ± 7, 15 male) were first assessed behaviourally outside the scanner with tests for actual tool use, pantomime and imitation of tool-use gestures, as well as for meaningless gesture imitation. Second, functional magnetic resonance imaging activity was registered during the passive observation of videos showing tool-associated actions. Voxel-wise linear regression analyses were used to identify areas where behavioural performance was correlated with functional magnetic resonance imaging activity. Furthermore, lesions were delineated on the magnetic resonance imaging scans for voxel-based lesion-symptom mapping. The analyses revealed two sets of regions where functional magnetic resonance imaging activity was associated with better performance in the clinical tasks. First, activity in left hemisphere areas thought to mediate cognitive motor functions in healthy individuals (i.e. activity within the putative 'healthy' network) was correlated with better scores. Within this network, tool-associated tasks were mainly related to activity in supramarginal gyrus and ventral premotor cortex, while meaningless gesture imitation depended more on the anterior intraparietal sulcus and superior parietal lobule. Second, repeating the regression analyses with total left hemisphere lesion volume as additional covariate demonstrated that tool-related skills were further supported by right premotor, right inferior frontal and left anterior temporal areas, while meaningless gesture imitation was also driven by the left dorso-lateral prefrontal cortex. In summary, tool-related and imitative skills in left hemisphere stroke patients depend on the activation of spared left hemisphere regions that support these abilities in healthy individuals. In addition, cognitive motor functions rely on the activation of ipsi- and contralesional areas that are situated outside this 'healthy' network. This activity may explain why some patients perform surprisingly well despite large left brain lesions, while others are severely impaired.
失用症是一种使人衰弱的认知运动障碍,常发生在左半球中风后,影响与工具相关的和模仿技能。然而,即使在具有相似病变的患者中,失用症的严重程度也存在差异。这种变异性提出了一个问题,即健康受试者中通常与认知运动任务相关的左半球网络以外的区域是否具有额外的功能相关性。为了研究这一假设,我们探讨了在左半球缺血性中风患者中,与认知运动表现更好相关的功能磁共振成像活动相关的区域。36 名患有慢性(>6 个月)大左半球梗死的患者(年龄±标准差,60±12 岁,29 名男性)和 29 名对照受试者(年龄±标准差,72±7 岁,15 名男性)首先在扫描仪外进行行为评估,使用实际工具使用、模仿和模仿工具使用手势的测试,以及无意义的手势模仿测试。其次,在观看显示工具相关动作的视频时记录功能磁共振成像活动。使用体素线性回归分析来确定与行为表现相关的功能磁共振成像活动的区域。此外,还在磁共振成像扫描中描绘了用于基于体素的病变-症状映射的病变。分析显示,两组与临床任务中表现更好相关的功能磁共振成像活动区域。首先,与健康个体中介导认知运动功能的左半球区域的活动(即所谓的“健康”网络内的活动)相关的功能磁共振成像活动与更好的分数相关。在这个网络中,与工具相关的任务主要与缘上回和腹侧运动前皮层的活动有关,而无意义的手势模仿则更多地依赖于前内顶叶沟和上顶叶叶。其次,使用左半球总病变体积作为附加协变量重复回归分析表明,工具相关技能进一步由右侧运动前区、右侧额下回和左侧前颞区支持,而无意义的手势模仿也由左侧背外侧前额叶皮层驱动。总之,左半球中风患者的工具相关和模仿技能依赖于保留的左半球区域的激活,这些区域在健康个体中支持这些能力。此外,认知运动功能依赖于同侧和对侧区域的激活,这些区域位于这个“健康”网络之外。这种活动可能解释了为什么一些患者尽管大脑左侧有大的病变,但表现却出人意料地好,而另一些患者则严重受损。
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