RESEARCH QUESTION: Can we enhance everyday cognition in older adults via working memory (WM) training & transcranial direct current stimulation (tDCS)?

RATIONALE: Older adulthood is associated with decline in WM, which can have a negative impact on continued participation in everyday activities, such as driving. WM training improves trained task performance but shows inconsistent transfer to untrained tasks, particularly in older adults. Previously, we paired WM training with tDCS and successfully elicited transfer in older adults. However, experiments were laboratory based. Here, we expand upon these findings by testing for meaningful cognitive gains in participants’ homes.

DESIGN: Longitudinal experimental design; participants completed transfer tasks at a preintervention home visit to establish a baseline and then, over 5 consecutive days, completed computerized WM training tasks and received tDCS. Following 1 mo of no contact, participants completed WM training tasks without tDCS, and we reassessed transfer task performance in their homes.

PARTICIPANTS: Ninety healthy older adults (ages 55–85 yr) participated. We excluded individuals with characteristics related to seizure risk with tDCS. All participants signed informed consent documents approved by the institutional review board. Participants were randomly assigned into three tDCS groups (Sham: placebo; Active1: 1 mA; Active2: 2 mA) and were reimbursed ($15/hr), and none left the study.

METHOD: Our WM training tasks included verbal/visual tasks coded on E-Prime^® software. Our standard transfer tasks, coded on MatLab^® software, included measures of processing speed, response inhibition, and arithmetic. Finally, our ecologically valid tests included the Weekly Calendar Planning Activity (WCPA) and cognitive parts of the OT–DORA.

ANALYSIS: We conducted parametric analyses using SPSS software. All participants improved on WM training tasks, and we observed no group differences in performance (analysis of variance, p = .974). We did observe group differences on transfer tasks. Active2 had significantly better performance than Active1 (p = .018) and Sham (p = .0004) on standard transfer tasks; this was represented by a composite benefit index—a calculated average of improvement on all three tasks from pre- to postintervention. Significant group differences were also observed on the WCPA and OT–DORA. On the WCPA, Active2 had significantly higher accuracy than Sham (p = .004). On the OT–DORA, both Active1 and Active2 significantly outperformed Sham (p = .005 and p = .024, respectively)

DISCUSSION: Older adults are cognitively vulnerable. Interventions that improve everyday cognition are in short supply, and those currently available show little wide-reaching benefit. We observed gains in all three groups on WM training tasks suggesting that training worked equally well for all participants. Two milliamperes of tDCS successfully induced significant benefits on both standard and ecologically valid transfer effects that were conducted in participants’ home environments.

IMPACT STATEMENT: These data support the use of WM training and tDCS protocols with older adults in research or clinical settings to promote sustained everyday cognitive ability in home and community settings. In other words, this intervention can elicit generalizable improvements in tasks relevant to everyday life and may facilitate prolonged and continued cognitive independence.