Department of Speech and Language Therapy, Istanbul Medipol University, Istanbul, Turkey.
Cortex. 2022 Oct;155:107-131. doi: 10.1016/j.cortex.2022.07.003. Epub 2022 Aug 3.
Neurocognitive models of language processing highlight the role of the left inferior frontal gyrus (IFG) in the functional network underlying language. Furthermore, neuroscience research has shown that IFG is not a uniform region anatomically, cytoarchitectonically or functionally. However, no previous study explored the language-related functional connectivity patterns of IFG subdivisions using a meta-analytic connectivity modeling (MACM) approach.
The present MACM study aimed to identify language-related coactivation patterns of the left and right IFG subdivisions.
Six regions of interest (ROIs) were defined using a probabilistic brain atlas corresponding to pars opercularis, pars triangularis and pars orbitalis of IFG in both hemispheres. The ROIs were used to search the BrainMap functional database to identify neuroimaging experiments with healthy, right-handed participants reporting language-related activations in each ROI. Activation likelihood estimation analyses were then performed on the foci extracted from the identified studies to compute functional convergence for each ROI, which was also contrasted with the other ROIs within the same hemisphere.
A primarily left-lateralized functional network was revealed for the left and right IFG subdivisions. The left-hemispheric ROIs exhibited more robust coactivation than the right-hemispheric ROIs. Particularly, the left pars opercularis was associated with the most extensive coactivation pattern involving bilateral frontal, bilateral parietal, left temporal, left subcortical, and right cerebellar regions, while the left pars triangularis and orbitalis revealed a predominantly left-lateralized involvement of frontotemporal regions.
The findings align with the neurocognitive models of language processing that propose a division of labor among the left IFG subdivisions and their respective functional networks. Also, the opercular part of left IFG stands out as a major hub in the language network with connections to diverse cortical, subcortical and cerebellar structures.
语言处理的神经认知模型强调了左额下回（IFG）在语言基础功能网络中的作用。此外，神经科学研究表明，IFG 在解剖学、细胞构筑学和功能上并不是一个统一的区域。然而，以前的研究没有使用元分析连接建模（MACM）方法来探索 IFG 细分的与语言相关的功能连接模式。
本 MACM 研究旨在确定左、右 IFG 细分的语言相关共激活模式。
使用对应于双侧 IFG 口角回、三角部和眶部的概率脑图谱定义了六个感兴趣区域（ROI）。使用这些 ROI 在 BrainMap 功能数据库中搜索，以识别报告每个 ROI 中与语言相关激活的健康右利手参与者的神经影像学实验。然后对从鉴定研究中提取的焦点进行激活似然估计分析，以计算每个 ROI 的功能收敛度，并与同一半球内的其他 ROI 进行对比。
揭示了左、右 IFG 细分的主要左侧功能网络。左半球 ROI 的共激活比右半球 ROI 更强。特别是，左侧口角回与最广泛的共激活模式相关，涉及双侧额叶、双侧顶叶、左侧颞叶、左侧皮质下和右侧小脑区域，而左侧三角部和眶部则显示出与额颞区主要左侧化的参与。
这些发现与语言处理的神经认知模型一致，该模型提出了左 IFG 细分及其各自的功能网络之间的分工。此外，左 IFG 的口角部作为语言网络中的一个主要枢纽，与不同的皮质、皮质下和小脑结构相连。
