老年人一体化编码的认知神经机制探索与干预研究：一种减少与老化相关的联结记忆缺陷的新途径

Unitized encoding enhances associative memory recognition by promoting familiarity-based retrieval. Older adults have impaired associative memory but generally preserved familiarity. Based upon these previous findings, the proposed project will investigate whether unitized encoding relative to non-unitized encoding reduces age-related associative memory difference as well as the underlying neurocognitive mechanisms. We will further carry out memory intervention based upon unitized encoding for older adults with subjective memory complaints, who are of high risk of Alzheimer's Disease (AD). We predict that unitized encoding will reduce age-related associative memory impairment by promoting familiarity-based retrieval. Unitized encoding is expected to relate to "entorhinal-frontal network" while non-unitized-encoding is associated with "hippocampal-retrosplenial/parietotemporal network".Compared to traditional memory strategy training which is non-unitized encoding, unitized encoding-based memory strategy training is supposed to have greater effects on memory function as well as everyday function for older adults with subjective memory complaints, and enhance entorhinal-frontal functional connectivity. The proposed project has the potential to reveal the underlying mechanisms of unitized encoding and to bring novel insights for understanding human memory. The project will also provide an efficient strategy to ameliorate the associative memory impairment of older adults, which have great implications for delaying cognitive aging and the onset of AD.

一体化编码促进熟悉性，进而支持联结记忆提取；老年人联结记忆受损，但熟悉性相对保留。本研究以此为切入点，结合行为学、ERP和fMRI技术，考察一体化编码相对于传统的非一体化编码是否可以减少老年人的联结记忆缺陷，探索相应的认知机制和神经环路基础。进而采用一体化编码策略，对有记忆主诉老年人开展干预研究。 预期会发现：一体化编码可以通过促进熟悉性提取减少联结记忆的年龄差异；一体化编码与"嗅周皮层-额叶"网络相关，而非一体化编码与"海马-压后皮层/顶颞叶"网络相关；相对于非一体化策略，一体化策略训练对有记忆主诉老人记忆功能和日常功能的促进作用更强，并能提升"嗅周皮层-额叶"功能连接。 该研究不仅有助于揭示一体化编码的加工机制，推动对人类记忆的深入理解，而且为解决老年人联结记忆缺陷提供一种更为有效的新途径，对于延缓认知老化和痴呆发生有重要意义。

以往研究提示当刺激材料在编码阶段得到一体化加工(unitization)时，熟悉性也能够支持联结记忆的提取过程；老年人虽然联结记忆受损，但是熟悉性相对保留完好。基于此，本项目首先采用合成词这一易于形成一体化表征的语言材料操纵一体化编码条件，接着采用定义法这一适合将词对编码成一个整体的新概念的方法来操纵一体化编码条件，以及交互表象法这种适合将项目和背景信息整合到一起的方法来操纵一体化编码条件，深入探索了一体化编码相对于传统的非一体化编码是否可以减少老年人的联结记忆缺陷，以及对应的认知机制和神经环路基础，并开展了相关认知训练研究。上述三项研究汇聚性地证明，相对于传统的非一体化编码条件，一体化编码能够有效地减少老年人的联结记忆损伤，其潜在原因是一体化编码能够增强熟悉性在联结记忆提取阶段中的贡献，一体化编码与“嗅周皮层-额叶”网络相关，而老年人由于熟悉性能力相对完好，所以能够充分利用这种一体化编码优势，最终其联结记忆成绩得以改善。该研究不仅进一步揭示了一体化编码的认知神经机制，推动对人类记忆的深入理解，而且为解决老年人联结记忆缺陷提供一种更为有效的新途径，对于延缓认知老化和痴呆发生有重要意义。