Moss Rehabilitation Research Institute, Elkins Park, PA 19027, USA.
Laboratory of Brain and Cognition, National Institute of Mental Health, NIH, Bethesda, MD 20892, USA.
Neuroimage Clin. 2019;21:101526. doi: 10.1016/j.nicl.2018.08.033. Epub 2018 Aug 31.
Increasing evidence indicates that focal lesions following stroke cause alterations in connectivity among functional brain networks. Functional connectivity between hemispheres has been shown to be particularly critical for predicting stroke-related behavioral deficits and recovery of motor function and attention. Much less is known, however, about the relevance of interhemispheric functional connectivity for cognitive abilities like praxis that rely on strongly lateralized brain networks. In the current study, we examine correlations between symptoms of apraxia-a disorder of skilled action that cannot be attributed to lower-level sensory or motor impairments-and spontaneous, resting brain activity in functional MRI in chronic left hemisphere stroke patients and neurologically-intact control participants. Using a data-driven approach, we identified 32 regions-of-interest in which pairwise functional connectivity correlated with two distinct measures of apraxia, even when controlling for age, head motion, lesion volume, and other artifacts: overall ability to pantomime the typical use of a tool, and disproportionate difficulty pantomiming the use of tools associated with different, competing use and grasp-to-move actions (e.g., setting a kitchen timer versus picking it up). Better performance on both measures correlated with stronger interhemispheric functional connectivity. Relevant regions in the right hemisphere were often homologous to left hemisphere areas associated with tool use and action. Additionally, relative to overall pantomime accuracy, disproportionate difficulty pantomiming the use of tools associated with competing use and grasp actions was associated with weakened functional connectivity among a more strongly left-lateralized and peri-Sylvian set of brain regions. Finally, patient performance on both measures of apraxia was best predicted by a model that incorporated information about lesion location and functional connectivity, and functional connectivity continued to explain unique variance in behavior even after accounting for lesion loci. These results indicate that interhemispheric functional connectivity is relevant even for a strongly lateralized cognitive ability like praxis and emphasize the importance of the right hemisphere in skilled action.
越来越多的证据表明，中风后的局灶性病变会导致功能脑网络之间的连接发生改变。已经证明，大脑半球之间的功能连接对于预测与中风相关的行为缺陷以及运动功能和注意力的恢复特别重要。然而，对于依赖于高度侧化脑网络的认知能力（如依赖实践的认知能力），大脑半球之间的功能连接的相关性知之甚少。在目前的研究中，我们研究了失用症（一种不能归因于较低水平的感觉或运动障碍的熟练动作障碍）的症状与慢性左半球中风患者和神经完整的对照参与者的功能磁共振成像中的自发静息脑活动之间的相关性。我们使用数据驱动的方法，在 32 个感兴趣的区域中，即使在控制年龄、头部运动、病变体积和其他伪影的情况下，功能连接与两种不同的失用症测量值相关：即模仿典型工具使用的整体能力，以及不成比例地难以模仿与不同、竞争使用和抓握动作相关的工具使用（例如，设置厨房定时器与将其拿起）。这两种措施的表现越好，与大脑半球之间的功能连接越强。右半球的相关区域通常与与工具使用和动作相关的左半球区域同源。此外，与整体模仿准确性相比，与竞争使用和抓握动作相关的工具使用不成比例地困难与一组更加偏侧化和颞旁的脑区之间的功能连接减弱有关。最后，患者在失用症的这两种测量方法上的表现都可以通过一个包含病变位置和功能连接信息的模型来最佳预测，并且即使在考虑到病变部位后，功能连接仍继续解释行为中的独特方差。这些结果表明，即使对于像实践这样的强烈侧化认知能力，大脑半球之间的功能连接也是相关的，并且强调了右半球在熟练动作中的重要性。
