As individuals age, they experience increased difficulties producing speech, especially with infrequent words. Older adults report that word retrieval difficulties frequently occur and are highly frustrating. However, little is known about how age affects the neural basis of language production. Moreover, age-related increases in brain activation are often observed, yet there is disagreement about whether such increases represent a form of neural compensation or dedifferentiation. We used functional magnetic resonance imaging (fMRI) to determine if there are age-related differences in functional activation during picture naming and whether such differences are consistent with a compensatory, dedifferentiation, or hybrid account that factors in difficulty. Healthy younger and older adults performed a picture-naming task with stimuli that varied in lexical frequency-our proxy for difficulty. Both younger and older adults were sensitive to lexical frequency behaviorally and neurally. However, younger adults performed more accurately overall and engaged both language (bilateral insula and temporal pole) and cognitive control (bilateral superior frontal gyri and left cingulate) regions to a greater extent than older adults when processing lower frequency items. In both groups, poorer performance was associated with increases in functional activation consistent with dedifferentiation. Moreover, there were age-related differences in the strength of these correlations, with better performing younger adults modulating the bilateral insula and temporal pole and better performing older adults modulating bilateral frontal pole and precuneus. Overall, these findings highlight the influence of task difficulty on fMRI activation in older adults and suggest that as task difficulty increases, older and younger adults rely on different neural resources. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

中文翻译：

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词汇频率会影响老年人和年轻人中图片命名的功能激活和准确性。

随着年龄的增长，他们说话的困难越来越大，尤其是很少说话的时候。老年人报告说，单词检索困难经常发生并且非常令人沮丧。但是，关于年龄如何影响语言产生的神经基础知之甚少。而且，经常观察到与年龄相关的大脑激活增加，但是对于这种增加代表神经补偿还是去分化形式存在分歧。我们使用功能磁共振成像（fMRI）来确定图片命名期间功能激活中是否存在与年龄相关的差异，以及这些差异是否与造成困难的补偿，去分化或混合因素一致。健康的年轻人和老年人执行图片命名任务时，刺激的词法频率各不相同，这是我们对困难的理解。年轻人和老年人都在行为和神经方面对词汇频率敏感。然而，在处理较低频率的项目时，较之成年人，年轻人的总体表现更为准确，并且在语言（双侧绝缘和颞极）和认知控制（双侧上额回和左扣带）两方面的参与程度都比老年人更大。两组中，较差的表现与去分化一致的功能激活增加有关。此外，这些关联的强度存在与年龄相关的差异，表现更好的年轻人调节双侧岛和颞极，表现更好的老年人调节双侧额叶和前突。总的来说，这些发现突出了任务难度对老年人功能磁共振成像激活的影响，并表明随着任务难度的增加，老年人和年轻人依赖不同的神经资源。（PsycINFO数据库记录（c）2020 APA，保留所有权利）。