Item recognition and lure discrimination in younger and older adults are supported by alpha/beta desynchronization

Abstract

Our episodic memories vary in their specificity, ranging from a mere sense of familiarity to detailed recollection of the initial experience. Recent work suggests that alpha/beta desynchronization promotes information flow through the cortex, tracking the richness in detail of recovered memory representations. At the same time, as we age, memories become less vivid and detailed, which may be reflected in age-related reductions in alpha/beta desynchronization during retrieval. To understand age differences in the specificity of episodic memories, we investigated differences in alpha/beta desynchronization between younger (18–26 years, n = 31) and older (65–76 years, n = 28) adults during item recognition and lure discrimination.Alpha/beta desynchronization increased linearly with the demand for memory specificity, i.e., the requirement to retrieve details for an accurate response, across retrieval situations (correct rejections < item recognition < lure discrimination). Stronger alpha/beta desynchronization was related to memory success, as indicated by reliable activation differences between correct and incorrect memory responses. In line with the assumption of a loss of mnemonic detail in older age, older adults had more difficulties than younger adults to discriminate lures from targets. Importantly, they also showed a reduced modulation of alpha/beta desynchronization across retrieval demands. Together, these results extend previous findings by demonstrating that alpha/beta desynchronization dissociates between item recognition and the retrieval of highly detailed memories as required in lure discrimination, and that age-related impairments in episodic retrieval are accompanied by attenuated modulations in the alpha/beta band. Thus, we provide novel findings suggesting that alpha/beta desynchronization tracks mnemonic specificity and that changes in these oscillatory mechanisms may underlie age-related declines in episodic memory.

Alpha/beta power decreases during episodic memory formation predict the magnitude of alpha/beta power decreases during subsequent retrieval

“…This matches numerous previous studies linking alpha/beta power decreases to successful memory retrieval (e.g. Griffiths et al, 2020;Griffiths, Mayhew, et al, 2019;Karlsson et al, 2020;Khader & Rösler, 2011;Martín-Buro et al, 2020;Michelmann et al, 2016;Waldhauser et al, 2016).…”

“…Similarly, the extended alpha/beta power decreases we observed during retrieval match the timing of the retrieval success effect, including both the rapidonset power decreases (Waldhauser et al, 2016) and those which last for extended periods of time (>1000ms; e.g. Karlsson et al, 2020;Martín-Buro et al, 2020;Michelmann et al, 2016). Given this overlap, it seems reasonable to suggest that the observed contingency between encoding-and retrieval-related alpha/beta power decreases directly relates to the same neurophysiological phenomena associated with the subsequent memory and retrieval success effects.…”

“…Fell et al, 2008;Griffiths et al, 2016;Hanslmayr et al, 2009), while the timing of the retrieval-related power decreases matches that of the retrieval success effect (e.g. Karlsson et al, 2020;Martín-Buro et al, 2020;Michelmann et al, 2016;Waldhauser et al, 2016).…”

“…Theories have proposed that these decreases support information representation by suppressing background noise or by increasing entropy within the network (Hanslmayr et al, 2012). Several studies have provided empirical support for these ideas by demonstrating that alpha/beta power decreases parametrically scale with the amount of information encoded as, or retrieved from, an episodic memory (Griffiths et al, 2020;Griffiths, Mayhew, et al, 2019;Karlsson et al, 2020;Martín-Buro et al, 2020).…”

“…Given that these noise correlations share a strong positive correlation with local field potential (LFP; Cui et al, 2016), one could speculate that the ubiquitous reduction in alpha/beta power that arises during task engagement (e.g., Crone et al, 1998;Krause et al, 1994;Pfurtscheller et al, 1996) may reflect a reduction in underlying noise correlations. In line with this idea, growing evidence suggests that alpha/beta power decreases support the representation of information encoded within, and retrieved from, episodic memories (Griffiths et al, 2020;Griffiths, Mayhew, et al, 2019;Karlsson et al, 2020;Martín-Buro et al, 2020). For example, a simultaneous EEG-fMRI study demonstrated that the magnitude of alpha/beta power decreases directly correlated with the amount of stimulus-specific information represented within the BOLD signal during both perception and episodic memory retrieval (Griffiths, Mayhew, et al, 2019).…”