A neuronal sign of persistent developmental stuttering is the magnified coactivation of right frontal brain regions during speech production. Whether and how stuttering severity relates to the connection strength of these hyperactive right frontal areas to other brain areas is an open question. Scrutinizing such brain–behaviour and structure–function relationships aims at disentangling suspected underlying neuronal mechanisms of stuttering. Here, we acquired diffusion-weighted and functional images from 31 adults who stutter and 34 matched control participants. Using a newly developed structural connectivity measure, we calculated voxel-wise correlations between connection strength and stuttering severity within tract volumes that originated from functionally hyperactive right frontal regions. Correlation analyses revealed that with increasing speech motor deficits the connection strength increased in the right frontal aslant tract, the right anterior thalamic radiation, and in U-shaped projections underneath the right precentral sulcus. In contrast, with decreasing speech motor deficits connection strength increased in the right uncinate fasciculus. Additional group comparisons of whole-brain white matter skeletons replicated the previously reported reduction of fractional anisotropy in the left and right superior longitudinal fasciculus as well as at the junction of right frontal aslant tract and right superior longitudinal fasciculus in adults who stutter compared to control participants. Overall, our investigation suggests that right fronto-temporal networks play a compensatory role as a fluency enhancing mechanism. In contrast, the increased connection strength within subcortical-cortical pathways may be implied in an overly active global response suppression mechanism in stuttering. Altogether, this combined functional MRI–diffusion tensor imaging study disentangles different networks involved in the neuronal underpinnings of the speech motor deficit in persistent developmental stuttering.

中文翻译：

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右额叶过度活动区的结构连通性随口吃严重程度而变

持续发展性口吃的神经元迹象是语音产生过程中右额脑区域的协同激活。口吃的严重性是否以及如何与这些多动的右额叶区域与其他大脑区域的连接强度有关，这是一个悬而未决的问题。仔细研究这种大脑行为与结构功能关系的目的在于弄清口吃的潜在潜在神经元机制。在这里，我们从31位口吃的成年人和34位匹配的对照参与者那里获得了扩散加权和功能图像。使用一项新开发的结构连通性度量，我们计算了连接强度与源于功能亢进的右额叶区域的道区域内口吃严重程度之间的体素相关性。相关分析表明，随着语音运动障碍的增加，右额叶前斜道，右前丘脑辐射以及右前中央沟下方的U形投影的连接强度也随之增加。相反，随着语音运动障碍的减少，右束状筋膜中的连接强度增加。全脑白质骨骼的其他组比较重复了先前报道的成人口吃与对照组相比口吃的成年人左，右上纵筋膜以及右额斜道与右上纵筋膜交界处的分数各向异性的降低。总体而言，我们的调查表明，正确的额颞网络在提高流利度方面起着补偿作用。相比之下，口吃过程中过度活跃的整体反应抑制机制可能暗示着皮层下-皮层通路内连接强度的增加。总而言之，这项功能性MRI扩散张量成像的组合研究可以消除持续发展性口吃时言语运动缺陷的神经元基础所涉及的不同网络。