Behavioral Sciences Department, James A. Haley Veterans' Hospital, Tampa, FL, USA.
Center for Cognitive Aging and Memory, McKnight Brain Institute, University of Florida, Gainesville, FL, USA.
Geroscience. 2024 Dec;46(6):6195-6212. doi: 10.1007/s11357-024-01216-x. Epub 2024 May 31.
The extent to which the neural systems underlying semantic processes degrade with advanced age remains unresolved, which motivated the current study of neural activation on functional magnetic resonance imaging (fMRI) during semantic judgments of associated vs. unassociated, semantic vs. rhyme, and abstract vs. rhyme word pairs. Thirty-eight older adults, 55-85 years of age, performed semantic association decision tasks in a mixed event-related block fMRI paradigm involving binary judgments as to whether word pairs were related (i.e., semantically associated). As hypothesized, significantly greater activation was evident during processing of associated (vs. unassociated) word pairs in cortical areas implicated in semantic processing, including the angular gyrus, temporal cortex, and inferior frontal cortex. Cortical areas showed greater activation to unassociated (vs. associated) word pairs, primarily within a large occipital cluster. Greater activation was evident in cortical areas when response to semantic vs. phonemic word pairs. Contrasting activation during abstract vs. concrete semantic processing revealed areas of co-activation to both semantic classes, and areas that had greater response to either abstract or concrete word pairs. Neural activation across conditions did not vary as a function of greater age, indicating only minimal age-associated perturbation in neural activation during semantic processing. Therefore, the response of the semantic hubs, semantic control, and secondary association areas appear to be largely preserved with advanced age among older adults exhibiting successful cognitive aging. These findings may provide a useful clinical contrast if compared to activation among adults experiencing cognitive decline due Alzheimer's, frontal-temporal dementia, and other neurodegenerative diseases.
语义过程所依赖的神经系统在多大程度上随着年龄的增长而退化仍未解决，这促使我们在功能磁共振成像（fMRI）上研究与联想词对相比，非联想词对、语义词对与韵词对、抽象词对与韵词对的神经激活情况。38 名年龄在 55-85 岁的老年人在混合事件相关的 fMRI 范式中执行语义联想决策任务，涉及到对词对是否相关（即语义上相关）的二分类判断。正如假设的那样，在处理联想词对（与非联想词对相比）时，与语义处理相关的皮质区域（包括角回、颞叶和下额叶）显示出明显更大的激活。皮质区域显示出对非联想词对（与联想词对相比）更大的激活，主要在一个大的枕叶簇内。在处理语义词对与音位词对时，大脑皮质区域的激活更大。对比抽象语义处理与具体语义处理的激活情况显示出了两个语义类别的共同激活区域，以及对抽象或具体词对有更大反应的区域。跨条件的神经激活并不随年龄的增加而变化，这表明在语义处理过程中，神经激活只有很小的年龄相关干扰。因此，在表现出成功认知老化的老年人中，语义枢纽、语义控制和二级联想区域的反应似乎在很大程度上得到了保留。如果与因阿尔茨海默病、额颞叶痴呆和其他神经退行性疾病而认知能力下降的成年人的激活情况进行比较，这些发现可能提供有用的临床对比。
