Ford Jaclyn H, Kensinger Elizabeth A
Department of Psychology, Boston College, Chestnut Hill, Massachusetts 02467
Department of Psychology, Boston College, Chestnut Hill, Massachusetts 02467.
J Neurosci. 2017 May 17;37(20):5172-5182. doi: 10.1523/JNEUROSCI.0521-17.2017. Epub 2017 Apr 25.
Over the last several decades, neuroimaging research has identified age-related neural changes that occur during cognitive tasks. These changes are used to help researchers identify functional changes that contribute to age-related impairments in cognitive performance. One commonly reported example of such a change is an age-related decrease in the recruitment of posterior sensory regions coupled with an increased recruitment of prefrontal regions across multiple cognitive tasks. This shift is often described as a compensatory recruitment of prefrontal regions due to age-related sensory-processing deficits in posterior regions. However, age is not only associated with spatial shifts in recruitment, but also with temporal shifts, in which younger and older adults recruit the same neural region at different points in a task trial. The current study examines the possible contribution of temporal modifications in the often-reported posterior-anterior shift. Participants, ages 19-85, took part in a memory retrieval task with a protracted retrieval trial consisting of an initial memory search phase and a subsequent detail elaboration phase. Age-related neural patterns during search replicated prior reports of age-related decreases in posterior recruitment and increases in prefrontal recruitment. However, during the later elaboration phase, the same posterior regions were associated with age-related increases in activation. Further, ROI and functional connectivity results suggest that these posterior regions function similarly during search and elaboration. These results suggest that the often-reported posterior-anterior shift may not reflect the inability of older adults to engage in sensory processing, but rather a change in when they recruit this processing. The current study provides evidence that the often-reported posterior-anterior shift in aging may not reflect a global sensory-processing deficit, as has often been reported, but rather a temporal modification in this processing in which older adults engage the same neural regions during a detail elaboration phase that younger adults engage during memory search. In other words, older adults may ultimately be able to engage the same processes as younger adults during some cognitive tasks when given the time to do so. Future research should examine the generalizability of this effect and the importance of encouraging older adults to engage in these processes through task instruction or questions.
在过去几十年中，神经影像学研究已经确定了在认知任务期间发生的与年龄相关的神经变化。这些变化有助于研究人员识别导致认知表现中与年龄相关损伤的功能变化。这种变化的一个常见例子是，在多个认知任务中，后感觉区域的激活减少与前额叶区域的激活增加与年龄相关。这种转变通常被描述为由于后区域与年龄相关的感觉处理缺陷而导致的前额叶区域的代偿性激活。然而，年龄不仅与激活的空间转移有关，还与时间转移有关，即年轻人和老年人在任务试验的不同时间点激活相同的神经区域。本研究考察了在经常报道的后-前转移中时间改变的可能作用。19-85岁的参与者参加了一项记忆检索任务，该任务包括一个初始记忆搜索阶段和随后的细节阐述阶段的长时间检索试验。搜索过程中与年龄相关的神经模式重复了先前关于后区域激活与年龄相关减少和前额叶激活增加的报道。然而，在随后的阐述阶段，相同的后区域与年龄相关的激活增加有关。此外，感兴趣区域（ROI）和功能连接结果表明，这些后区域在搜索和阐述过程中的功能相似。这些结果表明，经常报道的后-前转移可能并不反映老年人无法进行感觉处理，而是反映了他们进行这种处理的时间变化。本研究提供的证据表明，在衰老过程中经常报道的后-前转移可能并不像经常报道的那样反映全局感觉处理缺陷，而是这种处理的时间改变，即老年人在细节阐述阶段激活与年轻人在记忆搜索阶段激活相同的神经区域。换句话说，在某些认知任务中，如果给老年人足够的时间，他们最终可能能够与年轻人进行相同的处理。未来的研究应该考察这种效应的普遍性，以及通过任务指导或问题鼓励老年人进行这些处理的重要性。
