The effect of transcranial alternating current stimulation (tACS) on cognitive function in older adults with dementia.

Recent studies have shown a positive effect of transcranial alternating current stimulation (tACS), a noninvasive brain stimulation technique, on cognitive function of healthy individuals [1]. However, investigation into the effects of tACS on individuals with dementia or mild cognitive impairment (MCI) is lacking. In this pilot study, we investigated the hypothesis that following a regular schedule of challenging brain exercises combined with simultaneous tACS application would improve the working memory and cognitive function of older adults with memory impairments. Further, we explored whether pairing brain exercises with tACS would result in longer-lasting positive effects on cognitive function than brain exercises alone. A total of 17 older adults (12 males, 5 females, 70 ± 7 years), each with a diagnosis of mild to moderate dementia were enrolled in the study. All participants completed brain exercises in the lab on the following schedule: two 30-minute sessions per day, 5 days/week for 4 weeks consecutively. Eleven of the participants received brain exercises paired with tACS application at 40Hz. We evaluated cognitive function of the participants at baseline, post-intervention and 1-month followup using the Wechsler Memory Scale (WMS-IV) as an independent assessment of our brain exercises. Both the non-tACS and tACS groups significantly improved their WMS scores from baseline to post-intervention assessments. Comparison of the post-intervention and 1-month follow-up assessments indicated that the tACS group maintained their improvement significantly better than the non-tACS group.