In the case of event-related potentials (ERPs), numerous studies have demonstrated that correctly identified old (studied) items elicit waveforms that are more positive-going than the ERPs elicited by correctly rejected new (unstudied) items. This ‘old/new ERP effects’ were identified as the neural correlates of episodic retrieval and have been fractionated into several temporally, topographically and functionally distinct sub-effects. There were also studies reporting a negative ‘old/new effect’—more positive-going waveforms elected by correctly judged new items than old items. This negative ‘old/new ERP effect’ remains a subject of much disagreement and less is known about the influence of aging on this effect. The present research compared the negative ‘old/new ERP effect’ between the young adults and healthy older adults in multiple memory tasks, including item memory (direct recognition, indirect repetition) and source memory tasks. Then, the negative ‘old/new ERP effect’ associated with source memory was selected as the outcome measure both in pre-test and post-test to examine the neural effect of memory training on episodic retrieval. According to our results, the negative ‘old/new ERP effect’ was observed in the young adults in both item memory (indirect repetition) and source memory tasks. Compared with the young adults, the negative ‘old/new ERP effect’ of the older adults disappeared in the item memory task and increased in the source memory task. This effect was increased further in left prefrontal scalp site after 16 sessions of memory training. Based on these observations, we proposed that the negative ‘old/new ERP effect’ reflected the search and/or activation of sensory-based information. The increased magnitude of this effect in older adult implied their reliance on the search and/or activation of sensory-based information in retrieving source information, in order to optimize their retrieval performance. The healthy older adults indeed benefited from memory training and they might stably use their retrieval strategy to optimize their performance even after memory training. Cognitive training in older adults might operate to enhance the brain’s functioning by promoting the old adults’ compensation process/strategy. Note that we did not observe expected effect in direct recognition item memory task, which might be attribute to the task design.
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