Physiological arousal during encoding predicts emotional memory: An aging study of phasic and tonic skin conductance activity

It is widely understood that declarative memory and emotion are interconnected, although they are differentially affected by aging. However, the contributions of various aspects of physiological arousal to emotional memory, as well as the roles of valence and age in these relationships, remain unknown. This study aimed to understand the relationship between various aspects of physiological arousal and memory in younger and older adults by examining phasic and tonic skin conductance activity during an emotional verbal learning task. We recruited 26 younger adults (aged 18-35) and 24 older adults (aged 55-89), asking them to encode and recall a list of positive, negative, and neutral words across three learning trials while their skin conductance activity was measured, and to recall the words again after 10 min. We found that both groups recalled more positive and negative words than neutral words in the delayed recall trial. A positive valence effect on memory specific to the encoding phase also emerged, which aligned with a significant phasic skin conductance response (SCR) to positive words. The phasic SCR while encoding positive words predicted the subsequent recall of positive words, while tonic skin conductance level, which was lower in older adults, predicted retention of negative words after the 10-minute delay. These findings suggest that physiological arousal during encoding predicts subsequent emotional memory across different ages, with phasic and tonic arousal making the greatest contributions to positive and negative memories, respectively. Age may differentially influence tonic arousal, which affects memory, particularly for negative stimuli.