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The present fMRI study aimed to characterize the performance and the brain activity changes related to episodic memory retrieval in adults with single domain aMCI (sdaMCI), relative to cognitively unimpaired adults. Participants performed an old/new recognition memory task with words while BOLD signal was acquired. The sdaMCI group showed lower hits (correct recognition of old words), lower ability to discriminate old and new words, higher errors and longer reaction times for hits. This group also displayed brain hypoactivation in left precuneus and the left midcingulate cortex during the successful recognition of old words. These changes in brain activity suggest the presence of neural dysregulations in brain regions involved during successful episodic memory retrieval. Moreover, hypoactivation in these brain areas discriminated both groups with moderate sensitivity and specificity values, suggesting that it might constitute a potential neurocognitive biomarker of sdaMCI This study was supported by grants from the Spanish Government, Ministerio de Economía y Competitividad (PSI2014–55316-C3–3-R; PSI2017–89389-C2–2-R; PID2020–114521RB-C21/C22); and the Galician Government, Axudas para a Consolidación e Estruturación de Unidades de Investigación Competitivas do Sistema Universitario de Galicia: GRC (GI-1807-USC. Ref: ED431–2017/27; ED431C-2021/04. All with ERDF/FEDER funds SI

Studies that have attempted to determine the effects of aging on the brain neural sources of memory retrieval have reported two contrasting age effects: under-recruitment and over-recruitment of several prefrontal areas. However, the causes for these effects are still a matter of debate. In order to study the underlying factors that cause the effects, we compared brain activation in young and older adults, in a successful word retrieval condition, and a failed word retrieval condition: the tip-of-the-tongue state. For this, we used the event-related potentials technique and neural source estimation with low-resolution tomographies. The results showed that the older adults did not display under-recruitment in any brain area in comparison with the young adults. However, they displayed additional prefrontal activation that varied depending on the processing stage and the condition, which supports the hypothesis of selective over-recruitment in older adults.

This study examined the effects of aging on the ERP components associated with the different processing stages in a face naming task. Two hundred photographs were presented to 13 young and 10 elderly adults, who had to press a button and then to say the name aloud (KNOW condition), or “Can’t remember” if they were experiencing a tip-of-the-tongue state (TOT condition). Young adults showed larger ERP amplitudes in KNOW than in TOT in the 550–750 and 1550–2000 ms intervals, but the older adults did not show any such differences. The older adults showed a specific lengthening in ERP latencies from 250 ms onwards, and smaller mean amplitudes in the 550–750 ms interval in the KNOW category and in the 750–1000 ms interval in both categories, and a wider and more frontalized scalp topographical distribution of the ERP amplitudes than the young adults. The results may indicate activation of compensatory mechanisms in elderly adults.