Peripheral nerve stimulation using tDCS can enhance reconsolidation but cannot mitigate retrieval-induced forgetting

Memory reconsolidation refers to the process by which reactivated memories are rendered labile - and can be further strengthened or become sensitive to disruption. This study investigated whether non-invasive transcutaneous electrical stimulation of the greater occipital nerve (NITESGON) using direct current stimulation (tDCS) can modulate reconsolidation processes.

In a randomised, double-blind, placebo-controlled experiment, 38 healthy participants completed a Swahili-English paired-association task across three sessions over two consecutive days. Active or sham NITESGON was applied during reconsolidation, to test its effects on retrieval practice and retrieval-induced forgetting.

Active NITESGON significantly enhanced memory reconsolidation, as evidenced by superior retrieval of previously consolidated pairs (i.e. no-change pairs) compared to sham stimulation. However, critically, we demonstrate that NITESGON did not mitigate retrieval-induced forgetting: both groups exhibited greater forgetting of competing associations (competing pairs) than non-competing ones (original pairs). This study also highlights how active NITESGON (compared to sham) significantly enhanced consolidation, but not acquisition or forgetting processes.

These findings demonstrate that peripheral nerve stimulation via tDCS can strengthen reconsolidation through retrieval practice, but does not alter retrieval-induced forgetting. This work elucidates the stage-specific influence of peripheral nerve stimulation on memory processes and highlights its potential translational value for conditions involving memory dysfunction.