Age-related Differences in Mu Rhythm During Emotional Destination Memory Task

Abstract

Background: Destination memory defined as the ability to remember to whom we addressed a piece of information is found to be impaired in normal aging. Theories of affect development and research findings have shown that emotional charging improves performance on memory tasks, and also that Mu rhythm is desynchronized as an index of mirror neuron activation during such tasks. Objective: In this paper, we sought to investigate the differences in Mu rhythm during an emotional destination memory task, between younger and older adults. Methods: 16 cognitively normal older adults, recruited from Alzheimer’s disease day center and 16 young adults, recruited via advertisements, participated in this experimental study. We investigated destination memory of emotionally charged faces (Emotional Destination Memory, EDM) while applying electroencephalograph (EEG) in real time in young versus older adults. We measured Mu rhythm in frontal, fronto-temporal and central areas. EEG data has been pre-processed, segmented in non-overlapping epochs, and independent component analysis (ICA) has been conducted to reject artifacts. Results: Results showed that young adults performed better than older adults in remembering facts associated with angry faces. Also, different neurophysiological activation was found, with older adults showing Mu suppression in frontal and fronto-temporal regions, specifically in F3, F7 and F8 electrodes, in contrast with young adults who showed Mu enhancement. Regarding within group differences, it was found that in the older adults group, electrodes F8 and central C3 were the most activated, while in the young adults group, C3 was the most activated electrode. Conclusion: The findings suggest better behavioral performance of young adults as a result of better cognitive state and adaptive bias. On a neurophysiological level, it is suggested that older adults employ Mu suppression, thus possible activation of mirror neurons, as a compensatory mechanism while mirroring properties are not spontaneously activated in young adults.