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

Abstract

<jats:title>Abstract</jats:title><jats:p>Episodic memory retrieval is characterised by the vivid reinstatement of information about a personally-experienced event. Growing evidence suggests that the reinstatement of such information is supported by reductions in the spectral power of alpha/beta activity. Given that the amount of information that can be recalled depends on the amount of information that was originally encoded, information-based accounts of alpha/beta activity would suggest that retrieval-related alpha/beta power decreases similarly depend upon decreases in alpha/beta power during encoding. To test this hypothesis, seventeen human participants completed a sequence-learning task while undergoing concurrent MEG recordings. Regression-based analyses were then used to estimate how alpha/beta power decreases during encoding predicted alpha/beta power decreases during retrieval, on a trial-by-trial basis. When subjecting these parameter estimates to group-level analysis, we find evidence to suggest that retrieval-related alpha/beta (7-15Hz) power decreases fluctuate as a function of encoding-related alpha/beta power decreases. These results suggest that retrieval-related alpha/beta power decreases are contingent on the decrease in alpha/beta power that arose during encoding. Subsequent analysis uncovered no evidence to suggest that these alpha/beta power decreases reflect stimulus identity, indicating that the contingency between encoding- and retrieval-related alpha/beta power reflects the reinstatement of a neurophysiological operation, rather than neural representation, during episodic memory retrieval.</jats:p>

Disentangling neocortical alpha/beta and hippocampal theta/gamma oscillations in human episodic memory formation

“…Moreover, interfering with these power decreases via transcranial magnetic brain stimulation impairs episodic memory formation . Together, these findings (see also Fellner et al, 2013;Griffiths et al, 2021;Karlsson et al, 2020;Long & Kahana, 2015;Martín-Buro et al, 2020;Sederberg et al, 2007) suggest that alpha/beta power decreases are intimately tied to the successful representation of information pertaining to episodic memories.…”

Oscillatory correlates of selective restudy

“…Indeed, while it appears likely that the effect reflects some form of memory reactivation, it is unclear whether this reactivation reflects context retrieval, as is suggested by the two-factor framework (Bäuml, 2019), or reactivation of the restudied items themselves. In the literature, (parietal) alpha power decrease has been suggested to be positively related to memory reactivation in both short-term (Klimesch et al, 2005) and long-term memory tasks (Griffiths et al, 2021;Martín-Buro et al, 2020). For instance, Martín-Buro et al (2020) examined alpha power decrease during recognition testing and found that left posterior alpha power decrease was positively related to both item recognition and associative recall.…”

“…For instance, Martín-Buro et al (2020) examined alpha power decrease during recognition testing and found that left posterior alpha power decrease was positively related to both item recognition and associative recall. Griffiths et al (2021) examined alpha/beta power decrease with recall testing and argued that alpha/beta power decrease may be unrelated to the reactivation of stimulus-specific information but related to "supportive processes" that accompany the encoding and retrieval of episodic memories.…”

“…In a recent EEG study, Griffiths et al (2021) showed that, on a trial-by-trial basis, an alpha/beta power decrease during encoding can predict an alpha/beta power decrease during retrieval. The findings suggest that a decrease in retrieval-related alpha/beta power can be contingent on the decrease in alpha/beta power that was found during encoding.…”

“…Critically, the observed decreases in alpha/beta power were not found to reflect stimulus identity, suggesting that the contingency between encoding-related and retrievalrelated alpha/beta power reflects the reactivation of a neurophysiological operation, rather than neural representation. Griffiths et al (2021) called this neurophysiological operation "supportive processes". We suggest that the decrease in alpha/beta power during study may reflect the encoding of context and the decrease in alpha/beta power during retrieval the reactivation of study context.…”