Transcranial direct current stimulation enhances offline consolidation of implicit sequential learning in individuals...

Insomnia not only compromises sleep quality but may also impair learning and memory processes within cognitive function.

This study aims to investigate the effects of transcranial direct current stimulation (tDCS) on offline consolidation of implicit sequence learning and sleep quality in individuals with insomnia.

We employed a randomized, double-blind, controlled trial, assigning individuals with insomnia to either an active stimulation group or a sham stimulation group for consecutive 7-day interventions. Sleep quality (PSQI) and implicit sequence learning performance were assessed before and after the intervention.

Forty-two participants with insomnia were randomly assigned to the active stimulation group (n = 21) or sham stimulation group (n = 21). Repeated-measures ANOVA revealed significant Group × Time interactions for both sleep quality (PSQI: F(1, 40) = 31.375, p < 0.001, η_p² = 0.440) and offline consolidation of implicit sequence learning (F(1, 40) = 7.913, p = 0.008, η_p² = 0.165). Post hoc analyses showed that, following the 7-day intervention, the active stimulation group exhibited significantly lower PSQI scores and greater offline consolidation effects compared with the sham stimulation group (both p < 0.01), whereas no significant improvements were observed in the sham stimulation group.

The 7-day tDCS intervention not only effectively improved sleep quality in individuals with insomnia but also enhanced offline consolidation effects in implicit sequence learning, providing new evidence for non-pharmacological interventions for insomnia.