Moss Rehabilitation Research Institute, Elkins Park, PA, USA; University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
Moss Rehabilitation Research Institute, Elkins Park, PA, USA.
Cortex. 2023 May;162:81-95. doi: 10.1016/j.cortex.2023.01.010. Epub 2023 Mar 6.
Dual-route models of high-level (praxis) actions distinguish between an "indirect" semantic route mediating meaningful gesture imitation, and a "direct" sensory-motor route mediates meaningless gesture imitation. Similarly, dual-route language models distinguish between an indirect route mediating production and repetition of words, and a direct route mediating non-word repetition. Although aphasia and limb apraxia frequently co-occur following left-hemisphere cerebrovascular accident (LCVA), it is unclear which aspects of these functional-neuroanatomic dual-route architectures are shared across praxis and language domains. This study focused on gesture imitation to test the hypothesis that semantic information (and portions of the indirect route) are shared across domains, whereas two distinct dorsal routes mediate sensory-motor mapping. Forty chronic LCVA and 17 neurotypical controls completed semantic memory and language tasks and imitated 3 types of gesture stimuli: (1) labeled/"named" meaningful, (2) unnamed meaningful, and (3) meaningless gestures. The comparison of accuracy between meaningless versus unnamed meaningful gestures examined the benefits of semantic information, while the comparison of unnamed meaningful versus named meaningful imitation examined additional benefits of linguistic cueing. Mixed-effects models examined group by task interaction effects on gesture ability. We found that for patients with LCVA, unnamed meaningful gestures were imitated more accurately than meaningless gestures, suggesting that semantic information was beneficial, but there was no benefit of labeling. Reduced benefit of semantic information on gesture accuracy was associated with lesions to inferior frontal and posterior temporal regions as well as semantic memory performance on a pictorial (non-gesture) task. In contrast, there was no relationship between meaningless gesture imitation and nonword repetition, indicating that measures of direct route performance are not associated across language and action. These results provide preliminary evidence that portions of the indirect semantic route are shared across the language and action domains, while two direct sensory-motor mapping routes mediate word repetition and gesture imitation.
双路径模型区分了高水平（动作）的间接语义路径和直接感觉运动路径。间接语义路径介导有意义的手势模仿，而直接感觉运动路径则介导无意义的手势模仿。同样，双路径语言模型也区分了间接路径介导单词的产生和重复，以及直接路径介导非单词重复。尽管左半球中风（LCVA）后常同时出现失语症和肢体运动障碍，但这些功能神经解剖双路径结构的哪些方面在动作和语言领域是共享的还不清楚。本研究专注于手势模仿，以检验以下假设：语义信息（以及间接路径的某些部分）在不同领域共享，而两个不同的背侧路径介导感觉运动映射。40 名慢性 LCVA 患者和 17 名神经典型对照组完成了语义记忆和语言任务，并模仿了 3 种手势刺激：（1）有标签/“命名”的有意义的，（2）无标签的有意义的，和（3）无意义的手势。比较无意义与无标签有意义手势的准确性检验了语义信息的益处，而比较无标签有意义与有标签有意义模仿检验了语言提示的额外益处。混合效应模型检验了组间任务交互效应对手势能力的影响。我们发现，对于 LCVA 患者，无标签有意义的手势模仿得更准确，这表明语义信息是有益的，但标签没有益处。语义信息对手势准确性的益处降低与额下回和颞后区的病变以及图片（非手势）任务的语义记忆表现有关。相比之下，无意义手势模仿与非单词重复之间没有关系，这表明语言和动作之间的直接路径表现测量没有关联。这些结果初步表明，间接语义路径的某些部分在语言和动作领域是共享的，而两个直接感觉运动映射路径介导单词重复和手势模仿。
