Vibrotactile stimulation selectively enhances motor memory consolidation in adults with ADHD: A diagnosis-specific effect

Task-irrelevant sensory stimulation represents a potential non-pharmacological intervention to optimize arousal states during procedural learning; this may benefit adults with ADHD wherein arousal dysregulation may limit memory formation. Ninety-seven young adults (65 unmedicated ADHD, 32 controls; ages 19–35) were randomized to motor sequence training with or without concurrent low-intensity vibrotactile stimulation (VtSt) via a vibrating cushion. Correct sequences and errors per 30-second block were assessed across acquisition, overnight consolidation (24 h), and retention (1-week) phases. Acute VtSt effects were tested at one-week. Post-training actigraphy-derived sleep-wake parameters and chronotype (MEQ) were evaluated as consolidation-phase gain predictors. A linear mixed-effects model with Diagnosis, Condition, Wave, and Timepoint as fixed factors revealed that VtSt did not affect acquisition. A significant Diagnosis × Condition × Timepoint interaction (p = 0.006) emerged. In ADHD, VtSt selectively enhanced overnight consolidation gains (p = 0.025, Cohen’s d = 0.40), with numerically superior performance maintained through 1-week (p = 0.060); acute VtSt re-presentation at 1-week enhanced performance (p = 0.020). In ADHD, consolidation gains were predicted by chronotype (β = 0.289, p = 0.024) and VtSt condition (β = 0.334, p = 0.010) but not sleep-wake parameters. Controls showed no significant VtSt effects at any re-test. When trained with VtSt, ADHD participants, but not controls, showed larger consolidation gains, sustained through 1-week retention. These findings support arousal optimization models and a precision medicine framework wherein chronotype and ADHD diagnosis may stratify individuals by intervention responsiveness and optimal timing for sensory-environmental intervention.