Xiao Xiangyue, Dong Zhicai, Yu Mingyan, Ding Junhua, Zhang Maolin, Cruz Sara, Han Zaizhu, Chen Yan
School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou 311121, China.
Key Laboratory of Aging and Cancer Biology of Zhejiang Province, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou 311121, China.
Brain Commun. 2024 Feb 21;6(2):fcae058. doi: 10.1093/braincomms/fcae058. eCollection 2024.
The hub-and-spoke theory of semantic representation fractionates the neural underpinning of semantic knowledge into two essential components: the sensorimotor modality-specific regions and a crucially important semantic hub region. Our previous study in patients with semantic dementia has found that the hub region is located in the left fusiform gyrus. However, because this region is located within the brain damage in patients with semantic dementia, it is not clear whether the semantic deficit is caused by structural damage to the hub region itself or by its disconnection from other brain regions. Stroke patients do not have any damage to the left fusiform gyrus, but exhibit amodal and modality-specific deficits in semantic processing. Therefore, in this study, we validated the semantic hub region from a brain network perspective in 79 stroke patients and explored the white matter connections associated with it. First, we collected data of diffusion-weighted imaging and behavioural performance on general semantic tasks and modality-specific semantic tasks (assessing object knowledge on form, colour, motion, sound, manipulation and function). We then used correlation and regression analyses to examine the association between the nodal degree values of brain regions in the whole-brain structural network and general semantic performance in the stroke patients. The results revealed that the connectivity of the left fusiform gyrus significantly predicted general semantic performance, indicating that this region is the semantic hub. To identify the semantic-relevant connections of the semantic hub, we then correlated the white matter integrity values of each tract connected to the left fusiform gyrus separately with performance on general and modality-specific semantic processing. We found that the hub region accomplished general semantic processing through white matter connections with the left superior temporal pole, middle temporal gyrus, inferior temporal gyrus and hippocampus. The connectivity between the hub region and the left hippocampus, superior temporal pole, middle temporal gyrus, inferior temporal gyrus and parahippocampal gyrus was differentially involved in object form, colour, motion, sound, manipulation and function processing. After statistically removing the effects of potential confounding variables (i.e. whole-brain lesion volume, lesion volume of regions of interest and performance on non-semantic control tasks), the observed effects remained significant. Together, our findings support the role of the left fusiform gyrus as a semantic hub region in stroke patients and reveal its crucial connectivity in the network. This study provides new insights and evidence for the neuroanatomical organization of semantic memory in the human brain.
语义表征的中心-辐条理论将语义知识的神经基础分为两个基本组成部分:特定感觉运动模态区域和一个至关重要的语义中心区域。我们之前对语义性痴呆患者的研究发现,中心区域位于左侧梭状回。然而,由于该区域位于语义性痴呆患者的脑损伤范围内,目前尚不清楚语义缺陷是由中心区域本身的结构损伤还是由其与其他脑区的连接中断所致。中风患者左侧梭状回没有任何损伤,但在语义处理方面表现出非模态和特定模态的缺陷。因此,在本研究中,我们从脑网络角度在79例中风患者中验证了语义中心区域,并探索了与之相关的白质连接。首先,我们收集了扩散加权成像数据以及在一般语义任务和特定模态语义任务(评估物体在形状、颜色、运动、声音、操作和功能方面的知识)上的行为表现数据。然后,我们使用相关性和回归分析来检验全脑结构网络中脑区的节点度值与中风患者一般语义表现之间的关联。结果显示,左侧梭状回的连通性显著预测了一般语义表现,表明该区域是语义中心。为了确定语义中心的语义相关连接,我们随后将连接到左侧梭状回的每条纤维束的白质完整性值分别与一般和特定模态语义处理的表现进行相关性分析。我们发现,中心区域通过与左侧颞上极、颞中回、颞下回和海马体的白质连接来完成一般语义处理。中心区域与左侧海马体、颞上极、颞中回、颞下回和海马旁回之间的连通性在物体形状、颜色、运动、声音、操作和功能处理中发挥着不同的作用。在统计学上消除潜在混杂变量的影响(即全脑病变体积、感兴趣区域的病变体积和非语义控制任务的表现)后,观察到的效应仍然显著。总之,我们的研究结果支持左侧梭状回作为中风患者语义中心区域的作用,并揭示了其在网络中的关键连通性。本研究为人类大脑中语义记忆的神经解剖组织提供了新的见解和证据。