HERA模型与来源记忆老化

HERA MODEL AND AGING OF SOURCE MEMORY

以考查来源记忆老化与来源记忆过程中额叶激活模式的关系为目的.采用行为测验和fMRI(功能磁共振成像)技术,以位置记忆为任务,对15位年轻人和13位老年人在来源记忆过程中的额叶激活模式进行比较.行为结果表明位置记忆存在显著年龄差异.脑成像结果表明:1)编码阶段在2个难度条件下,老年人和年轻人的额叶激活都表现出左侧优势;提取阶段在2个难度条件下,老年人和年轻人的激活模式都没有表现出单侧化倾向.HERA模型不具有跨年龄和任务的普遍性;2)在低难度任务中,编码和提取阶段老年人与年轻人的额叶激活模式基本相同,老年人的激活面积稍大;在高难度任务中,编码阶段除额下回老年人比年轻人激活稍多外,年轻人的激活脑区明显多于老年人.提取阶段,老年人和年轻人的激活的脑区基本没有差异.来源记忆老化与加工过程的关系还需要进一步探讨.

This study investigated the relation between aging of source memory and pattern of frontal cortex activation during encoding and retrieval processes,in order to verify the HERA model across ages and taskes,as well as to explore which process is closely related to performance decline of source memory during aging.Both behavioral measurements and fMRI scanns were done in 15 young and 13 old adults.Two levels（easy verses difficult） of location memory tasks were presented with a block design while scanning.Brain scanning was taken during encoding and retrieval processes,frontal cortex activation was recorded.Images during encoding and retrieval were compared.Behavioral results showed significant age differences on location recall performances.Brain imaging results suggested that,during encoding process,under both difficult and easy conditions,older people had the same pattern of lateralized activation as their younger counterparts,namely the left frontal cortex was more activated.In the retrieval process,however,both groups did not show lateralization on frontal cortex activation regardless the tasks.Data also showed that,when comparing between groups with respect to encoding process,older people had slightly more areas activated in frontal cortex than young people under both easy and difficult task conditions.While young people showed no more significant activation than older people with easy task,they presented distinctively more activation in difficult task.Finally,when comparing between groups with respect to retrieval process for both tasks,only inferior frontal gyrus was found to be more activated in older group.Two conclusions can be drawn from this study.First,HERA model was evident in encoding but not retrieval process of source memory.Hence it was not a general model in terms of age and task.Secondly,aging effects on performance of source memory may be related to the encoding process with aging.