Can transcranial direct current stimulation enhance outcomes from cognitive training? A randomized controlled trial in healthy participants

Black Dog Institute, Sydney, Australia.
The International Journal of Neuropsychopharmacology (Impact Factor: 4.01). 05/2013; 16(09):1-10. DOI: 10.1017/S1461145713000539
Source: PubMed


Computer-administered cognitive training (CT) tasks are a common component of cognitive remediation treatments. There is growing evidence that transcranial direct current stimulation (tDCS), when given during cognitive tasks, improves performance. This randomized, controlled trial explored the potential synergistic effects of CT combined with tDCS in healthy participants. Altogether, 60 healthy participants were randomized to receive either active or sham tDCS administered during training on an adaptive CT task (dual n-back task), or tDCS alone, over 10 daily sessions. Cognitive testing (working memory, processing speed, executive function, reaction time) was conducted at baseline, end of the 10 sessions, and at 4-wk follow-up to examine potential transfer effects to non-trained tasks. Altogether, 54 participants completed the study. Over the 10 'online' sessions, participants in the active tDCS+CT condition performed more accurately on the CT task than participants who received sham tDCS+CT. The performance enhancing effect, however, was present only during tDCS and did not result in greater learning (i.e. improvement over sessions) on the CT task. These results confirm prior reports of enhancement of cognitive function during tDCS stimulation. At follow-up, the active tDCS+CT group, but not the sham tDCS+CT group, showed greater gains on a non-trained test of attention and working memory than the tDCS-only group (p < 0.01). Although this gain can mainly be attributable to training, this result suggests that active tDCS may have a role in further enhancing outcomes.

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    • "Given some optimism surrounding working memory training, future trials may reveal additive or synergistic benefits from combining behavioral cognitive remediation treatments with neurostimulation or pharmacological approaches. For example , recent studies in healthy individuals have reported benefits of the application of noninvasive transcranial direct current stimulation (tDCS) with cognitive training in working memory, attention, and verbal learning (Martin et al., 2013; Richmond, Wolk, Chien, & Olson, 2014 "
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    ABSTRACT: Deficits in learning and memory are commonly observed after traumatic brain injury (TBI); however, the mechanisms underlying such deficits are poorly understood. This study examines the contribution of other cognitive processes in verbal learning after moderate to severe TBI. Adults with TBI who have verbal learning deficits were predicted to perform worse on executive measures than adults who are able to learn. Participants were 51 community-dwelling adult volunteers (age 18-59) with moderate to severe TBI. Injury severity was determined by Glasgow Coma Scale score ≤12 and corroborating information from medical records. Group membership (TBI-learners or TBI-nonlearners) was determined by a learning criterion of perfect recall on 2 consecutive trials within 15 trials on the open-trial Selective Reminding Test. All participants completed a comprehensive neuropsychological test battery. Group differences were examined using independent-samples t tests, and logistic regression was used to determine significant predictors of learning ability. The TBI-learner group performed better than the TBI-nonlearner group most consistently on tasks of executive control and working memory. Results of a logistic regression showed that working memory capacity was the most significant predictor of learning ability after TBI. Working memory significantly influences the ability to learn verbal information after TBI. The documented relationship between working memory and learning will guide the development of more efficacious treatments to rehabilitate learning and memory deficits after TBI.
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    • "In MCI [37] and AD [33], CCT combined with ChEIs had significantly greater benefit on memory and other cognitive measures than ChEIs alone. Similarly, the burgeoning field of research investigating the benefit of transcranial deep cortical stimulation (tDCS) indicates that the combination of CT with tDCS enhanced cognitive performance, and importantly this benefit was on nontrained tasks [73]. Although at the preliminary research stage, this research suggests that the combination of CT with tDCS may have a synergistic effect, thus magnifying the benefit of CT as a treatment option. "
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    ABSTRACT: There is much interest in early intervention for the prevention or postponement of dementia in Alzheimer's disease (AD). The results of drugs trials in this regard have thus far been disappointing, and non-pharmacological interventions are receiving increased attention. One such intervention is complex cognitive activity. Evidence from epidemiological studies suggests that participation in stimulating mental activities is associated with lowered dementia risk. The introduction of novel and complex cognitive interventions to healthy adults and those with cognitive impairment may represent an efficacious treatment option to improve cognition, lower dementia incidence, and slow rate of decline. This review examines the evidence for restorative cognitive training (CT) and addresses a number of clinically relevant issues regarding cognitive benefit and its transfer and persistence. Although the number of randomized controlled trials is limited, preliminary evidence suggests that CT may provide immediate and longer term cognitive benefits which generalize to non-trained domains and non-cognitive functions, with supervised small group multi-domain training providing greatest benefits. Possible neuroplastic mechanisms are discussed, and recommendations for further research and clinical implementation provided.
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    • " visual and auditory streams ( Martin et al . , 2013 ) . Despite these methodological differences , both we and Martin et al . ( 2013 ) find evidence that tDCS en - hances learning in the domain of WM and this enhance - ment extends beyond a simple enhanced practice effect to conceptually similar tasks . In addition , both studies ( current work ; Martin et al . , 2013 ) failed to find any evi - dence of far transfer effects following tDCS - enhanced WM training after exposure to a limited number of practice sessions , suggesting that additional training + tDCS may be needed to produce far transfer ."
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    ABSTRACT: Studies attempting to increase working memory (WM) capacity show promise in enhancing related cognitive functions but have also raised criticism in the broader scientific community given the inconsistent findings produced by these studies. Transcranial direct current stimulation (tDCS) has been shown to enhance WM performance in a single session [Fregni, F., Boggio, P., Nitsche, M., Bermpohl, F., Anatal, A., Feredoes, E., et al. Anodal transcranial direct current stimulation of prefrontal cortex enhances working memory. Experimental Brain Research, 166, 23-30, 2005]; however, the extent to which tDCS might enhance learning on a WM training regime and the extent to which learning gains might transfer outside the training task remains largely unknown. To this end, participants engaged in an adaptive WM training task [previously utilized in Richmond, L., Morrison, A., Chein, J., & Olson, I. Working memory training and transfer in older adults. Psychology & Aging, 26, 813-822, 2011; Chein, J., & Morrison, A. Expanding the mind's workspace: Training and transfer effects with a complex working memory span task. Psychonomic Bulletin & Review, 17, 193-199, 2010] for 10 sessions over 2 weeks, concurrent with either active or sham stimulation of dorsolateral pFC. Before and after training, a battery of tests tapping domains known to relate to WM abilities was administered. Results show that tDCS enhanced learning on the verbal portion of the training task by 3.65 items. Furthermore, tDCS was shown to enhance near transfer to other untrained WM tasks in comparison with a no-contact control group. These results lend support to the idea that tDCS might bolster training and transfer gains in populations with compromised WM abilities.
    Journal of Cognitive Neuroscience 04/2014; 26(11). DOI:10.1162/jocn_a_00657 · 4.09 Impact Factor
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