Department of Neurology, Medical University of South Carolina, 96 Jonathan Lucas St, Charleston, SC 29425, USA.
Department of Neurology, Johns Hopkins University, School of Medicine, Phipps 446, 600 N Broadway, Baltimore, MD 21287, USA.
Brain. 2019 Dec 1;142(12):3951-3962. doi: 10.1093/brain/awz309.
Non-fluent speech is one of the most common impairments in post-stroke aphasia. The rehabilitation of non-fluent speech in aphasia is particularly challenging as patients are rarely able to produce and practice fluent speech production. Speech entrainment is a behavioural technique that enables patients with non-fluent aphasia to speak fluently. However, its mechanisms are not well understood and the level of improved fluency with speech entrainment varies among individuals with non-fluent aphasia. In this study, we evaluated the behavioural and neuroanatomical factors associated with better speech fluency with the aid of speech entrainment during the training phase of speech entrainment. We used a lesion-symptom mapping approach to define the relationship between chronic stroke location on MRI and the number of different words per second produced during speech entrainment versus picture description spontaneous speech. The behavioural variable of interest was the speech entrainment/picture description ratio, which, if ≥1, indicated an increase in speech output during speech entrainment compared to picture description. We used machine learning (shallow neural network) to assess the statistical significance and out-of-sample predictive accuracy of the neuroanatomical model, and its regional contributors. We observed that better assisted speech (higher speech entrainment/picture description ratio) was achieved by individuals who had preservation of the posterior middle temporal gyrus, inferior fronto-occipital fasciculus and uncinate fasciculus, while exhibiting lesions in areas typically associated with non-fluent aphasia, such as the superior longitudinal fasciculus, precentral, inferior frontal, supramarginal and insular cortices. Our findings suggest that individuals with dorsal stream damage but preservation of ventral stream structures are more likely to achieve more fluent speech with the aid of speech entrainment compared to spontaneous speech. This observation provides insight into the mechanisms of non-fluent speech in aphasia and has potential implications for future research using speech entrainment for rehabilitation of non-fluent aphasia.
非流畅性言语是脑卒中后失语症患者最常见的障碍之一。由于患者很少能够流利地产生和练习言语，因此失语症患者的非流畅性言语康复尤其具有挑战性。语音同步是一种行为技术，可使非流畅性失语症患者说话流利。然而，其机制尚不清楚，并且语音同步对非流畅性失语症患者的流利度改善程度因人而异。在这项研究中，我们在语音同步的训练阶段，借助语音同步来评估与更好的言语流畅性相关的行为和神经解剖学因素。我们使用病变-症状映射方法来定义 MRI 上慢性脑卒中的位置与语音同步与图片描述自发言语期间每秒说出的不同单词数之间的关系。行为学上的关注点是语音同步/图片描述比，其如果≥1，则表明在语音同步期间言语输出增加，与图片描述相比。我们使用机器学习（浅层神经网络）来评估神经解剖学模型的统计显著性和样本外预测准确性，以及其区域贡献者。我们发现，保留后颞中回、下额枕颞束和钩束，同时存在通常与非流畅性失语症相关的区域损伤，如上纵束、中央前回、额下回、缘上回和岛叶皮质，有助于实现更好的辅助言语（更高的语音同步/图片描述比）。我们的研究结果表明，与自发言语相比，具有背侧流损伤但保留腹侧流结构的个体在语音同步的辅助下更有可能实现更流利的言语。这一观察结果为失语症中不流畅性言语的机制提供了新的见解，并对未来使用语音同步治疗非流畅性失语症的研究具有潜在意义。
