Abstract
Working memory is an executive memory process essential for everyday decision-making and problem solving that declines with advanced age. Transcranial direct current stimulation (tDCS) is a non-invasive form of brain stimulation that has demonstrated potential for improving working memory performance in older adults. However, the neural mechanisms underlying effects of tDCS on working memory are not well understood. This mechanistic study investigated the acute and after-effects of bilateral frontal (F3/F4) tDCS at 2 mA for 12-min on functional connectivity of the working memory network in older adults. We hypothesized active tDCS over sham would increase frontal connectivity during working memory performance. The study used a double-blind within-subject 2 session crossover design. Participants performed an functional magnetic resonance imaging (fMRI) N-Back working memory task before, during, and after active or sham stimulation. Functional connectivity of the working memory network was assessed within and between stimulation conditions (FDR < 0.05). Active tDCS produced a significant increase in functional connectivity between left ventrolateral prefrontal cortex (VLPFC) and left dorsolateral PFC (DLPFC) during stimulation, but not after stimulation. Connectivity did not significantly increase with sham stimulation. In addition, our data demonstrated both state-dependent and time-dependent effects of tDCS working memory network connectivity in older adults. tDCS during working memory performance produces a selective change in functional connectivity of the working memory network in older adults. These data provide important mechanistic insight into the effects of tDCS on brain connectivity in older adults, as well as key methodological considerations for tDCS-working memory studies.
Highlights
Working memory enables us to remember, manipulate, and reorganize information for short periods of time (Salthouse et al, 1989; Baddeley, 1992, 2003)
Active A significant increase in functional connectivity was observed during-active stimulation compared to baseline-active when seeding in the left ventrolateral prefrontal cortex (VLPFC) targeting left dorsolateral prefrontal cortex (DLPFC) (P-FDR = 0.045)
Our results demonstrate the ability of in-scanner Transcranial direct current stimulation (tDCS) paired with an N-Back task to acutely modulate functional connectivity in the working memory network
Summary
Working memory enables us to remember, manipulate, and reorganize information for short periods of time (Salthouse et al, 1989; Baddeley, 1992, 2003). This executive memory process is fundamental for everyday life and is known to decline with advanced age (Li et al, 2001; Gazzaley et al, 2007). While there is growing evidence supporting the role of frontal structural and functional decline in age-related working memory performance, there is a lack of effective interventions aimed at treating this decline. Such interventions will be necessary for addressing public health concerns related to the increasing age of the world population and the increased prevalence of age-related cognitive decline in the population at large
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
