Younger and older adults utilize dissociable neural mechanisms to up-regulate encoding of visual long-term memory.

Abstract

Despite the virtually unlimited capacity of visual long-term memory (VLTM), our ability to encode new visual information into this offline storage fluctuates from moment to moment, thus rendering some information forgotten later in time. Is there any way to monitor this moment-to-moment fluctuation and correct them when needed in real time? Previously we have demonstrated that we can monitor this fluctuation from multiple electroencephalograms (EEG) measures of memory encoding in real time and intervene failed memory encoding by cueing participants to up-regulate (i.e.,“try harder”) memory encoding on the spot, particularly when the ongoing frontal theta (5–7Hz) amplitude was low (Pereira & Fukuda, 2018). In the current study, we examined whether older adults were capable of exerting the same up-regulatory control on VLTM encoding. Interestingly, although older adults exhibited the equivalent efficacy for voluntary up-regulation of VLTM encoding, the underlying neural correlates were qualitatively different from those for younger adults. More precisely, unlike younger adults, the older adults’ efficacy of voluntary up-regulation of VLTM encoding did not depend on the amplitude of ongoing frontal theta activity. Moreover, while the amplitude of the cue-elicited late posterior positivity predicted successful up-regulation of VLTM encoding in younger adults, it was not the case for the older adults. Taken together, our results demonstrate that younger and older adults recruit dissociable neural mechanisms to voluntarily up-regulate VLTM encoding, and thus suggest the importance of age-specific calibration of EEG-based real-time memory intervention.