Effects of combined cognitive training and transcranial direct current stimulation (tDCS) on self-reported everyday function in older adults

Emanuel Boutzoukas, University of Florida, Gainesville, United States
Andrew O'Shea, University of Florida, Gainesville, United States
George Hishaw, University of Arizona, Tucson, United States
Steven DeKosky, University of Florida, Gainesville, United States
Samuel Wu, University of Florida, Gainesville, United States
Michael Marsiske, University of Florida, Gainesville, United States
Gene Alexander, University of Arizona, Tuscon, United States
Ronald Cohen, University of Florida, Gainesville, United States
Adam Woods, University of Florida, Gainesville, United States


Cognitive Training (CT) has shown promise for improving cognition in older adults. However, evidence of long-lasting, far-transfer improvements to everyday function is limited. Combining CT with non-invasive brain stimulation techniques, like transcranial direct current stimulation (tDCS), may further enhance neuroplasticity and facilitate transfer to everyday function. This study investigated whether a 3-month combined CT+tDCS intervention could enhance long-lasting far-transfer effects on self-reported everyday function at 1-year follow-up.

Participants and Methods:

167 older adults ages 65-88 completed 40 hours of computerized CT over 12 weeks as part of the Augmenting Cognitive Training in Older Adults multisite trial. Participants were randomized to CT paired with either active tDCS (CT+tDCS; n=89) or sham stimulation (CT+Sham; n=79). tDCS was administered during CT daily for two weeks, then weekly for 10 weeks. Two electrodes in saline-soaked 5x7 cm2 sponges were placed over the frontal cortices using the 10-20 measurement system (Anode: F4; Cathode: F3). The CT+tDCS group received 2mA of current for 20 minutes. The CT+Sham group received 2mA for 30 seconds, then no current for the remaining 20 minutes. At baseline and post-intervention assessments, participants completed the Instrumental Activities of Daily Living (IADL) questionnaire, a self-report measure assessing difficulty completing daily tasks, including meal preparation, housework, finances, health maintenance, telephone use, and shopping. IADL Difficulty Scores were normalized using the rank-based Blom transformation. Linear regression assessed several predictors of 1-year IADL Difficulty, including IADL Difficulty at baseline, stimulation group, age, sex, years of education, and study site.


Multiple linear regression predicted 40% of the variance in the 1-year IADL Difficulty Score (p<0.001) with significant predictors of fewer difficulties including fewer baseline difficulties (β=0.54, p<0.001), stimulation group (β=-0.2, p<0.01), and study site (β=-0.18, p<0.01). Follow-up analyses showed that CT+tDCS participants reported fewer difficulties than CT+Sham counterparts, and the University of Arizona participants reported fewer difficulties relative to the University of Florida participants. Moderation analyses demonstrated a significant Baseline IADL*Stimulation Group interaction (β=-0.39, p<0.01) that was not influenced by study site.


These findings demonstrate the utility of combined CT+tDCS on everyday functional independence at 1-year post-intervention. Prior literature shows cognitive training reduces IADL Difficulty at 5- and 10 years post-training. The present study suggests that combined CT+tDCS may further protect against declines in everyday functional independence compared to CT alone. Ultimately, this work aims to identify novel methods for maximizing the real-world benefits of CT interventions for the remediation of cognitive decline in older adults.

Category: Aging

Keyword 1: aging (normal)
Keyword 2: neuromodulation
Keyword 3: activities of daily living