University of Florida, Department of Clinical and Health Psychology, Gainesville, FL, USA.
Neurobiol Aging. 2012 Apr;33(4):656-69. doi: 10.1016/j.neurobiolaging.2010.06.020. Epub 2010 Aug 8.
Previous functional imaging studies that compared activity patterns in older and younger adults during nonlinguistic tasks found evidence for 2 phenomena: older participants usually show more pronounced task-related positive activity in the brain hemisphere that is not dominant for the task and less pronounced negative task-related activity in temporo-parietal and midline brain regions. The combined effects of these phenomena and the impact on word retrieval, however, have not yet been assessed. We used functional magnetic resonance imaging to explore task-related positive (active task > baseline) and negative activity (baseline > active task) during semantic and phonemic verbal fluency tasks. Increased right frontal positive activity during the semantic task and reduced negative activity in the right hemisphere during both tasks was associated with reduced performance in older subjects. No substantial relationship between changes in positive and negative activity was observed in the older participants, pointing toward 2 partially independent but potentially co-occurring processes. Underlying causes of the observed functional network inefficiency during word retrieval in older adults need to be determined in the future.
先前的功能影像学研究比较了非语言任务中老年人和年轻人的活动模式，发现了以下两种现象的证据：与任务相关的正性活动在非优势大脑半球更为显著，颞顶和中线脑区的负性活动则不那么显著。然而，这些现象的综合影响及其对词汇提取的影响尚未得到评估。我们使用功能磁共振成像技术，探讨了语义和语音流畅性任务中与任务相关的正性（活跃任务>基线）和负性活动（基线>活跃任务）。在语义任务中，右侧额叶的正性活动增加，而在两个任务中，右侧半球的负性活动减少，与老年人的表现下降有关。在老年人中，没有观察到正性和负性活动变化之间的实质性关系，这表明存在两个部分独立但可能同时发生的过程。未来需要确定老年人词汇提取过程中观察到的功能网络效率低下的潜在原因。
