Iyer Kartik K, Copland David A, Angwin Anthony J
Faculty of Medicine, UQ Centre for Clinical Research, Royal Brisbane and Women's Hospital, The University of Queensland, Herston, Australia.
School of Health and Rehabilitation Sciences, The University of Queensland, St Lucia, Australia.
Brain Connect. 2022 Mar;12(2):164-173. doi: 10.1089/brain.2020.0867. Epub 2021 Sep 7.
It is well recognized that semantic processing and auditory repetition facilitate subsequent naming of pictures. However, the neurocognitive mechanisms that underpin these facilitation effects remain unclear. The current study utilized a dynamic causal modeling (DCM) approach to examine high-density electroencephalographic (128-channel EEG) recordings and investigate connectivity modulations during facilitated naming of pictures in 18 healthy older adults (mean age 61.50 years). Source reconstruction of event-related potentials was performed in two specific time windows, (1) 150-250 msec and (2) 300-500 msec, to establish the timescale of significant cortical activations present during participation of semantic and phonological tasks. Hypothesis-driven DCM of source-activated regions was tested to ascertain which model most likely explained the semantic and phonological conditions, respectively. DCM results indicated that a common cortical network comprising dorsal and ventral cortical connections best explained EEG task data derived from repetition and semantic tasks. For repetition (phonological) tasks, this model featured long feedback, bidirectional connections from inferior frontal gyrus (IFG) to occipitotemporal areas. Semantic tasks were most plausibly explained by a model that featured a self-inhibiting connection over the IFG only. Findings from this study reveal that a common cortical model comprising pathways that include dorsal and ventral regions is appropriate for characterizing EEG naming facilitation data, and that distinct cortical connections explain differences between semantic and auditory repetition processes. These models could be repurposed for naming facilitation paradigms in patients with language difficulties to optimize prediction and responsiveness to such paradigms. Impact statement The combination of semantic (word-level) and phonological (sound-level) processing in the cortex facilitates one of the most robust responses-the naming of pictures. Here, dynamic causal modeling of high-density electroencephalography during facilitated naming tasks revealed a model consisting of common dorsal and ventral connections that best explained response to semantic and phonological stimuli. Within this cortical network, phonological facilitation involved a long-range connection from inferior frontal gyrus (IFG) to occipitotemporal regions, whereas semantic facilitation contributed to self-inhibition of the IFG. The IFG is therefore a key region mediating cortical activity when switching between phonological and semantic conditions.
人们普遍认识到，语义加工和听觉复述有助于随后对图片进行命名。然而，支撑这些促进作用的神经认知机制仍不清楚。本研究采用动态因果模型（DCM）方法，对18名健康老年人（平均年龄61.50岁）在图片命名促进过程中的高密度脑电图（128导脑电图）记录进行分析，并研究连接性调制。在两个特定的时间窗口（1）150 - 250毫秒和（2）300 - 500毫秒内进行事件相关电位的源重建，以确定在语义和语音任务参与期间显著的皮质激活的时间尺度。对源激活区域进行假设驱动的DCM测试，以确定哪种模型最有可能分别解释语义和语音条件。DCM结果表明，一个由背侧和腹侧皮质连接组成的共同皮质网络最能解释从复述和语义任务中获得的脑电图任务数据。对于复述（语音）任务，该模型的特点是从额下回（IFG）到枕颞区的长反馈双向连接。语义任务最合理的解释是一个仅在IFG上具有自我抑制连接的模型。本研究结果表明，一个由包括背侧和腹侧区域的通路组成的共同皮质模型适用于表征脑电图命名促进数据，并且不同的皮质连接解释了语义和听觉复述过程之间存在的差异。这些模型可用于语言困难患者的命名促进范式，以优化对此类范式的预测和反应。影响声明：皮质中语义（单词水平）和语音（声音水平）加工的结合促进了最强烈的反应之一——图片命名。在此，在命名促进任务期间对高密度脑电图进行动态因果建模，揭示了一个由共同的背侧和腹侧连接组成的模型，该模型最能解释对语义和语音刺激的反应。在这个皮质网络中，语音促进涉及从额下回（IFG）到枕颞区的长程连接，而语义促进则导致IFG的自我抑制。因此，IFG是在语音和语义条件之间切换时介导皮质活动的关键区域。
