Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, 243 Charles Street, Suite 421, Boston, MA, 02114, USA.
Brain Struct Funct. 2018 Jun;223(5):2489-2498. doi: 10.1007/s00429-018-1644-y. Epub 2018 Mar 8.
The importance of insula in speech control is acknowledged but poorly understood, partly due to a variety of clinical symptoms resulting from insults to this structure. To clarify its structural organization within the speech network in healthy subjects, we used probabilistic diffusion tractography to examine insular connectivity with three cortical regions responsible for sound processing [Brodmann area (BA) 22], motor preparation (BA 44) and motor execution (laryngeal/orofacial primary motor cortex, BA 4). To assess insular reorganization in a speech disorder, we examined its structural connectivity in patients with spasmodic dysphonia (SD), a neurological condition that selectively affects speech production. We demonstrated structural segregation of insula into three non-overlapping regions, which receive distinct connections from BA 44 (anterior insula), BA 4 (mid-insula) and BA 22 (dorsal and posterior insula). There were no significant differences either in the number of streamlines connecting each insular subdivision to the cortical target or hemispheric lateralization of insular clusters and their projections between healthy subjects and SD patients. However, spatial distribution of the insular subdivisions connected to BA 4 and BA 44 was distinctly organized in healthy controls and SD patients, extending ventro-posteriorly in the former group and anterio-dorsally in the latter group. Our findings point to structural segregation of the insular sub-regions, which may be associated with the different aspects of sensorimotor and cognitive control of speech production. We suggest that distinct insular involvement may lead to different clinical manifestations when one or the other insular region and/or its connections undergo spatial reorganization.
岛叶在言语控制中的重要性已得到认可，但仍未被充分理解，部分原因是由于该结构受到损伤会导致各种临床症状。为了阐明其在健康受试者言语网络中的结构组织，我们使用概率弥散张量成像技术研究了岛叶与三个负责声音处理的皮质区域（Brodmann 区 22 区）、运动准备（44 区）和运动执行（喉/面初级运动皮质，4 区）的连接。为了评估言语障碍中的岛叶重组，我们检查了痉挛性发音障碍（SD）患者的岛叶结构连接，SD 是一种选择性影响言语产生的神经疾病。我们发现岛叶可以分为三个不重叠的区域，它们分别接收来自 44 区（前岛叶）、4 区（中岛叶）和 22 区（背侧和后岛叶）的不同连接。健康受试者和 SD 患者之间，连接每个岛叶亚区到皮质靶区的束线数量或岛叶簇及其投射的半球侧化没有显著差异。然而，与健康对照组和 SD 患者相比，连接到 BA 4 和 BA 44 的岛叶亚区的空间分布明显不同，前者呈腹后向延伸，后者呈前背向延伸。我们的研究结果表明岛叶亚区的结构分离，这可能与言语产生的感觉运动和认知控制的不同方面有关。我们提出，当一个或另一个岛叶区域及其连接经历空间重组时，可能会导致不同的临床表现。
