A - 10 Selective Serotonin Reuptake Inhibitors Do Not Alter HD-tDCS Effects on Episodic Memory in Cognitively Impaired Older Adults

Abstract Objective High-Definition Transcranial Direct Current Stimulation (HD-tDCS) is a potential new intervention for mild cognitive impairment (MCI) and Alzheimer’s Dementia (ad) involving small doses of electrical stimulation. Prior studies suggest potential interactions with Selective Serotonin Reuptake Inhibitors (SSRIs) that could alter HD-tDCS’s effectiveness on cognitive outcomes. This study evaluated if SSRIs altered HD-tDCS response to episodic memory functioning in individuals with MCI and ad. Method Eighteen individuals (M age = 70.5; 27.8% female; 8 stable on SSRIs), 9 with MCI and 9 with ad, underwent ten 20-minute HD-tDCS sessions of 1 milliampere over the medial frontal cortex. Neuropsychological testing assessed learning and delayed recall for visual (Brief Visuospatial Memory Test-Revised) and verbal (Rey Auditory Verbal Learning Test or Hopkins Verbal Learning Test-Revised) episodic memory at baseline and immediately post-treatment. Linear regressions evaluated SSRI use as a predictor of post-treatment episodic memory performance controlling for baseline scores. Results Ten participants demonstrated improvement on at least one measure by 0.5 standard deviation (SD; 5 T-score points), with 5 showing 1 SD improvement. Eleven showed a decline by 0.5 SD on at least one measure, with 7 showing 1 SD decline. SSRI use did not significantly predict better or worse verbal learning (β = −4.285, p = 0.194), verbal delayed recall (β-0.408, p = 0.883), visual learning (β = −2.788, p = 0.405), and visual delayed recall (β = −6.673, p = 0.150) performance post-HD-tDCS. Conclusion Preliminary findings suggest SSRIs may not impact HD-tDCS outcomes in cognitively impaired older adults, specifically for episodic memory. These results may not translate to other neuropsychological domains; however, larger samples are needed for further investigation.