tDCS-Induced Memory Reconsolidation Effects and Its Associations With Structural and Functional MRI Substrates in Subjective Cognitive Decline

Abstract

Previous evidence suggests that transcranial direct current stimulation (tDCS) to the left dorsolateral prefrontal cortex (l-DLPFC) can enhance episodic memory in subjects with subjective cognitive decline (SCD), known to be at risk of dementia. Our main goal was to replicate such findings in an independent sample and elucidate if baseline magnetic resonance imaging (MRI) characteristics predicted putative memory improvement. Thirty-eight participants with SCD (aged: 60–65 years) were randomly assigned to receive active (N = 19) or sham (N = 19) tDCS in a double-blind design. They underwent a verbal learning task with 15 words (DAY-1), and 24 h later (DAY-2) stimulation was applied for 15 min at 1.5 mA targeting the l-DLPFC after offering a contextual reminder. Delayed recall and recognition were measured 1 day after the stimulation session (DAY-3), and at 1-month follow-up (DAY-30). Before the experimental session, structural and functional MRI were acquired. We identified a group∗time interaction in recognition memory, being the active tDCS group able to maintain stable memory performance between DAY-3 and DAY-30. MRI results revealed that individuals with superior tDCS-induced effects on memory reconsolidation exhibited higher left temporal lobe thickness and greater intrinsic FC within the default-mode network. Present findings confirm that tDCS, through the modulation of memory reconsolidation, is capable of enhancing performance in people with self-perceived cognitive complaints. Results suggest that SCD subjects with more preserved structural and functional integrity might benefit from these interventions, promoting maintenance of cognitive function in a population at risk to develop dementia.

tDCS-Induced Memory Reconsolidation Effects: Analysis of Prominent Predicting Factors

“…Importantly, a recent study ( Vaqué-Alcázar et al, 2021 ) replicated our findings ( Manenti et al, 2017 ) in an independent sample, which confirmed that tDCS, through the modulation of memory reconsolidation, is capable of enhancing performance in people with SMC. This study also suggested that individuals with more preserved structural and functional integrity might benefit from this intervention.…”

Dose response of transcranial near infrared light stimulation on brain functional connectivity and cognition in older adults—A randomized comparison

“…Enhanced rsFC of the brain has been suggested as the mechanistic basis for the effects of other NIBS, such as tDCS and TMS, in depression, schizophrenia, and dementia [54][55][56][57]. An increase in rsFC in the default mode network (DMN) was also noted following PBM in stroke [22] and dementia [30].…”

Recent contributions to the field of subjective cognitive decline in aging: A literature review

“…An RCT measuring the effect of a combined transcranial direct current stimulation (tDCS) and mindfulness‐based stress reduction in individuals with SCD found that although feasible and safe, there were no statistically significant effects on outcome measures (i.e., mindfulness, social functioning, mood, subjective cognition and objective cognitive performance) compared to combined sham tDCS with mindfulness‐based stress reduction 149 . A double‐blind tDCS versus sham study found that individuals with SCD who had greater structural and functional brain integrity (per MRI) had the greatest tDCS‐induced memory consolidation effect, indicating these individuals may benefit most from this form of neuromodulation 150 . A study of repeated transcranial magnetic stimulation in older adults with SCD found evidence of enhanced visual working memory, and significantly improved attention and executive function when the left dorsolateral prefrontal cortex was stimulated 151 …”

“…149 A doubleblind tDCS versus sham study found that individuals with SCD who had greater structural and functional brain integrity (per MRI) had the greatest tDCS-induced memory consolidation effect, indicating these individuals may benefit most from this form of neuromodulation. 150 A study of repeated transcranial magnetic stimulation in older adults with SCD found evidence of enhanced visual working memory, and significantly improved attention and executive function when the left dorsolateral prefrontal cortex was stimulated. 151 In sum, data on recent interventions in SCD have been mixed.…”