Anderson N D, Iidaka T, Cabeza R, Kapur S, McIntosh A R, Craik F I
University of Toronto and Rotman Research Institute, Baycrest Centre for Geriatric Care, Toronto, Ontario, Canada.
J Cogn Neurosci. 2000 Sep;12(5):775-92. doi: 10.1162/089892900562598.
Divided attention (DA) disrupts episodic encoding, but has little effect on episodic retrieval. Furthermore, normal aging is associated with episodic memory impairments, and when young adults are made to encode information under DA conditions, their memory performance is reduced and resembles that of old adults working under full attention (FA) conditions. Together, these results suggest a common neurocognitive mechanism by which aging and DA during encoding disrupt memory performance. In the current study, we used PET to investigate younger and older adults' brain activity during encoding and retrieval under FA and DA conditions. In FA conditions, the old adults showed reduced activity in prefrontal regions that younger adults activated preferentially during encoding or retrieval, as well as increased activity in prefrontal regions young adults did not activate. These results indicate that prefrontal functional specificity of episodic memory is reduced by aging. During encoding, DA reduced memory performance, and reduced brain activity in left-prefrontal and medial-temporal lobe regions for both age groups, indicating that DA during encoding interferes with encoding processes that lead to better memory performance. During retrieval, memory performance and retrieval-related brain activity were relatively immune to DA for both age groups, suggesting that DA during retrieval does not interfere with the brain systems necessary for successful retrieval. Finally, left inferior prefrontal activity was reduced similarly by aging and by DA during encoding, suggesting that the behavioral correspondence between these effects is the result of a reduced ability to engage in elaborate encoding operations.
分散注意力（DA）会干扰情景记忆编码，但对情景记忆提取影响不大。此外，正常衰老与情景记忆受损有关，当年轻人在DA条件下进行信息编码时，他们的记忆表现会下降，类似于在全神贯注（FA）条件下工作的老年人的记忆表现。综合这些结果表明，衰老和编码过程中的DA通过一种共同的神经认知机制破坏记忆表现。在本研究中，我们使用正电子发射断层扫描（PET）来研究年轻人和老年人在FA和DA条件下编码和提取过程中的大脑活动。在FA条件下，老年人在编码或提取过程中年轻人优先激活的前额叶区域活动减少，而在年轻人未激活的前额叶区域活动增加。这些结果表明，衰老会降低情景记忆的前额叶功能特异性。在编码过程中，DA降低了记忆表现，并且两个年龄组的左前额叶和内侧颞叶区域的大脑活动均减少，这表明编码过程中的DA会干扰导致更好记忆表现的编码过程。在提取过程中，两个年龄组的记忆表现和与提取相关的大脑活动对DA相对不敏感，这表明提取过程中的DA不会干扰成功提取所需的大脑系统。最后，编码过程中衰老和DA同样会使左下前额叶活动减少，这表明这些效应之间的行为对应关系是由于进行精细编码操作的能力下降所致。
