Abstract: Negative emotions can promote the formation and maintenance of memory, which is adaptive for human survival. This may help us recall important information that is directly or indirectly related to future survival. However, it is unclear how this emotional enhancement of memory changes with aging. Currently, research on negative emotions has focused more on immediate recall, while delayed memory tasks have not been extensively studied. The present study investigated the effects of aging on the negative emotional enhancement of memory effect in delayed recall and the neural mechanisms underlying it.
The experiments used a 2 (age: young adults vs. older adults) × 2 (valence: neutral vs. negative) mixed design, with age as the between-subjects variable and valence as the within-subjects variable. The present study used a paradigm of visuospatial associative memory under delayed recall, which required young adults (n = 39) and older adults (n = 35) to process neutral and negative stimuli and remember the location of the stimulus on a map. This experiment comprised two distinct phases: the learning phase and the test phase. In the learning phase, participants were asked to repeat the learning process until they correctly recalled the correct location of all emotional pictures on the background map. In the test phase, a delayed recall condition was added in addition to the immediate recall condition, with a 12-hour interval between the immediate associative memory test and the delayed associative memory test.
The results showed that these young and older adults showed the same pattern of immediate recall. There was no significant difference in the immediate recall performance of neutral and negative stimuli between young and older adults. However, after 12 hours, older adults showed better delayed recall performance for associative memory for negative stimuli than for neutral stimuli, whereas there was no difference between the negative and the neutral conditions for young adults. After a delay, negative stimuli showed negative emotional enhancement effects in older adults'associative memory. Neural representation similarity analysis during the memory retrieval phase showed that there were significant differences in the emotional neural representation of the superior occipital gyrus and the ventrolateral prefrontal cortex between young adults and old adults. And the neural representation of the ventrolateral prefrontal cortex in older adults was significantly correlated with the accuracy of associative memory after a 12-hour delay. Moreover, the activation of the ventrolateral prefrontal cortex in older adults can significantly predict their associative memory performance after a 12-hour delay.
Delayed recall of negative stimuli shows greater adaptability and has survival implications. From an evolutionary perspective, negative emotional stimuli imply that an event is directly or indirectly related to survival. Preserving memory for negative emotional stimuli after a delay is more adaptive, thus ensuring that we can recall this important information in the future. This may be a protective mechanism that helps older adults adapt to dangerous information in the outside world and avoid injury in daily life.

Key words: emotional enhancement of memory effect, older adults, delayed recall, representational similarity, single-trial analysis

摘要： 负性情绪会促进记忆的形成和维持,具有生存意义。然而该情绪记忆增强效应随着年老化的变化以及年轻人和老年人在情绪视空间任务中延迟联结记忆及其神经表征的特点和差异尚不明确。即时回忆时老年人和年轻人展现出相同的记忆表现,而12小时后老年人负性刺激的记忆比中性刺激有更好的延迟回忆成绩,年轻人没有差异。老年人腹外侧前额叶皮层的神经表征与年轻人存在差异且与其延迟记忆正确率相关,同时单试次分析显示老年人该脑区的激活可以在试次水平预测其延迟后的联结记忆成绩。综上,负性情绪对老年人联结记忆有增强效应且在延迟后更加明显,这与其腹外侧前额叶皮层的神经表征相关,可能反映了老年人防御外界危险的保护机制。

关键词: 记忆增强效应, 老年人, 延迟回忆, 表征相似性, 单试次分析