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. 2019 Mar 15:11:51.
doi: 10.3389/fnagi.2019.00051. eCollection 2019.

Effects of in-Scanner Bilateral Frontal tDCS on Functional Connectivity of the Working Memory Network in Older Adults

Nicole R Nissim  1   2 , Andrew O'Shea  1 , Aprinda Indahlastari  1 , Rachel Telles  1 , Lindsey Richards  1 , Eric Porges  1 , Ronald Cohen  1 , Adam J Woods  1   2
Affiliations

Effects of in-Scanner Bilateral Frontal tDCS on Functional Connectivity of the Working Memory Network in Older Adults

Nicole R Nissim et al. Front Aging Neurosci. .

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.

Keywords: DLPFC (dorsolateral prefrontal cortex); cognitive aging; fMRI—functional magnetic resonance imaging; functional connectivity; tDCS; transcranial direct cortical stimulation (tDCS); working memory.

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Figures

Figure 1
Figure 1
Experimental design for the functional magnetic resonance imaging (fMRI) N-Back task. Participants underwent an N-Back task before (Baseline), during active or sham stimulation (During), and after stimulation was stopped (Post). Anode = red; Cathode = blue. A, anterior; P, posterior; L, left; R, right.
Figure 2
Figure 2
Example of a 2-Back version of N-Back.
Figure 3
Figure 3
Functional connectivity beta values in active vs. sham session contrasts (seeding left ventrolateral prefrontal cortex, VLPFC to target left dorsolateral PFC, DLPFC). *P-FDR < 0.05.
Figure 4
Figure 4
Seed to target locations for significant connectivity findings. See Table 2 for seed to target location names. Nodes colored in black represent the seed location. Nodes color coded in red or blue indicate the target location. Red signifies significantly increased connectivity (FDR < 0.05). Blue signifies significantly decreased connectivity (FDR < 0.05). A, anterior; P, posterior; R, right; L, left.
See this image and copyright information in PMC

References

    1. Andrews-Hanna J. R., Snyder A. Z., Vincent J. L., Lustig C., Head D., Raichle M. E., et al. . (2007). Disruption of large-scale brain systems in advanced aging. Neuron 56, 924–935. 10.1016/j.neuron.2007.10.038 - DOI - PMC - PubMed
    1. Baddeley A. (1992). Working memory. Science 255, 556–559. 10.1126/science.1736359 - DOI - PubMed
    1. Baddeley A. (2003). Working memory: looking back and looking forward. Nat. Rev. Neurosci. 4, 829–839. 10.1038/nrn1201 - DOI - PubMed
    1. Barbey A. K., Koenigs M., Grafman J. (2013). Dorsolateral prefrontal contributions to human working memory. Cortex 49, 1195–1205. 10.1016/j.cortex.2012.05.022 - DOI - PMC - PubMed
    1. Batsikadze G., Moliadze V., Paulus W., Kuo M.-F., Nitsche M. A. (2013). Partially non-linear stimulation intensity-dependent effects of direct current stimulation on motor cortex excitability in humans. J. Physiol. 591, 1987–2000. 10.1113/jphysiol.2012.249730 - DOI - PMC - PubMed