Does transcranial direct current stimulation enhance cognitive and motor functions in the ageing brain? A systematic review and meta- analysis

Abstract

The use of transcranial direct current stimulation (tDCS) to enhance cognitive and motor functions has enjoyed a massive increase in popularity. Modifying neuroplasticity via non-invasive cortical stimulation has enormous potential to slow or even reverse declines in functions associated with ageing. The current meta-analysis evaluated the effects of tDCS on cognitive and motor performance in healthy older adults. Of the 81 studies identified, 25 qualified for inclusion. A random effects model meta-analysis revealed a significant overall standardized mean difference equal to 0.53 (SE = 0.09; medium heterogeneity: I 2 = 57.08%; and high fail-safe: N = 448). Five analyses on moderator variables indicated significant tDCS beneficial effects: (a) on both cognitive and motor task performances, (b) across a wide-range of cognitive tasks, (c) on specific brain areas, (d) stimulation offline (before) or online (during) the cognitive and motor tasks. Although the meta-analysis revealed robust support for enhancing both cognitive and motor performance, we outline a number of caveats on the use of tDCS.

Individual Differences and Long-term Consequences of tDCS-augmented Cognitive Training

“…Several studies have demonstrated selective tDCS benefits among individuals with low, but not high, baseline WM abilities (Gozenman & Berryhill, 2016;Heinen et al, 2016;Tseng et al, 2012), and meta-analyses tend to report stronger effect sizes in clinical or older adult populations compared with the higher-performing young adult population (Dedoncker, Brunoni, Baeken, & Vanderhasselt, 2016;Hill, Fitzgerald, & Hoy, 2016;Hsu, Ku, Zanto, & Gazzaley, 2015;Summers, Kang, & Cauraugh, 2015). Moreover, the evidence extends beyond the WM domain.…”

Randomized trial of transcranial direct current stimulation for poststroke dysphagia

“…41 tDCS may therefore constitute a therapeutic option for a broad range of stroke patientsunless they suffer from stroke in those regions identified as being irresponsive to tDCS, predominantly the righthemispheric insula and opercular region. In line with this, a relevant age dependency for tDCS efficacy has not been described so far.…”

Brain Stimulation for Cognitive Enhancement in the Older Person: State of the Art and Future Directions

“…Recent reviews of the small number of studies of NIBS in older adults found similar benefits, with generally positive outcomes and good tolerability (Martins et al 2017;Summers et al 2016). Positive results include enhanced monitoring of errors (Harty et al 2014), reduced distractibility in a task (Kim et al 2012), facilitations in language performance (Fertonani et al 2014;Meinzer et al 2014) and improved memory (Berryhill and Jones 2012;Flöel et al 2012;Holland et al 2011;Manenti et al 2013).…”