Diaz Michele T, Rizio Avery A, Zhuang Jie
The Pennsylvania State University, University Park, PA, USA.
Brain Imaging and Analysis Center, Duke University School of Medicine, Durham, NC, USA.
Lang Linguist Compass. 2016 Jul;10(7):314-334. doi: 10.1111/lnc3.12199. Epub 2016 Jul 12.
Although healthy aging is generally characterized by declines in both brain structure and function, there is variability in the extent to which these changes result in observable cognitive decline. Specific to language, age-related differences in language production are observed more frequently than in language comprehension, although both are associated with increased right prefrontal cortex activation in older adults. The current paper explores these differences in the language system, integrating them with theories of behavioral and neural cognitive aging. Overall, data indicate that frontal reorganization of the dorsal language stream in older adults benefits task performance during comprehension, but not always during production. We interpret these results in the CRUNCH framework (compensation-related utilization of neural circuits hypothesis), which suggests that differences in task and process difficulty may underlie older adults' ability to successfully adapt. That is, older adults may be able to neurally adapt to less difficult tasks (i.e., comprehension), but fail to do so successfully as difficulty increases (i.e., production). We hypothesize greater age-related differences in aspects of language that rely more heavily on the dorsal language stream (e.g., syntax and production) and that recruit general cognitive resources that rely on frontal regions (e.g., executive function, working memory, inhibition). Moreover, there should be a relative sparing of tasks that rely predominantly on ventral stream regions. These results are both consistent with patterns of age-related structural decline and retention and with varying levels of difficulty across comprehension and production. This neurocognitive framework for understanding age-related differences in the language system centers on the interaction between prefrontal cortex activation, structural integrity, and task difficulty.
尽管健康衰老通常以大脑结构和功能的衰退为特征，但这些变化导致可观察到的认知衰退的程度存在差异。具体到语言方面，与年龄相关的语言产出差异比语言理解差异更常被观察到，尽管两者都与老年人右前额叶皮层激活增加有关。本文探讨了语言系统中的这些差异，并将它们与行为和神经认知衰老理论相结合。总体而言，数据表明老年人背侧语言流的额叶重组在理解过程中有利于任务表现，但在产出过程中并非总是如此。我们在CRUNCH框架（神经回路补偿相关利用假说）中解释这些结果，该假说表明任务和过程难度的差异可能是老年人成功适应能力的基础。也就是说，老年人可能能够在神经层面上适应较简单的任务（即理解），但随着难度增加（即产出），他们可能无法成功适应。我们假设在更依赖背侧语言流的语言方面（例如句法和产出）以及调用依赖额叶区域的一般认知资源（例如执行功能、工作记忆、抑制）方面，与年龄相关的差异更大。此外，主要依赖腹侧流区域的任务应该相对较少受到影响。这些结果既与年龄相关的结构衰退和保留模式一致，也与理解和产出过程中的不同难度水平一致。这个用于理解语言系统中与年龄相关差异的神经认知框架以额叶皮层激活、结构完整性和任务难度之间的相互作用为核心。
