Highlights
- •We report a meta-analysis of the effects from single-session tDCS on language studies.
- •There were many significant effects from single-session tDCS in healthy adults.
- •Anodal tDCS produced significant effects on verbal fluency and word learning.
- •Anodal tDCS using prefrontal stimulation produced significant effects on verbal fluency.
Abstract
Background
Transcranial direct current stimulation (tDCS) is a brain stimulation technique used
to examine causal relationships between brain regions and cognitive functions. The
effects from tDCS are complex, and the extent to which stimulation reliably affects
different cognitive domains is not fully understood and continues to be debated.
Objective/hypothesis
To conduct a meta-analysis of studies examining the effects of single-session anodal
tDCS on language.
Methods
The meta-analysis examined the behavioral results from eleven experiments of single-session
anodal tDCS and language processing in healthy adults. The means and standard deviations
of the outcome measures were extracted from each experiment and entered into the meta-analyses.
In the first analysis, we examined the effects of single-session tDCS across all language
studies. Next, a series of sub-analyses examined the effects of tDCS on specific tasks
and stimulation protocols.
Results
There was a significant effect from anodal single-session tDCS in healthy adults compared
to sham (P = 0.001) across all language measures. Next, we found significant effects on specific
stimulation protocols (e.g., offline measures, P = 0.002), as well as specific tasks and electrode montages (e.g., verbal fluency
measures and left prefrontal cortex, P = 0.035).
Conclusions
The results indicate that single-session tDCS produces significant and reliable effects
on language measures in healthy adults.
Keywords
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References
- Excitability changes induced in the human motor cortex by weak transcranial direct current stimulation.J Physiol. 2000; 527: 633-639
- Sustained excitability elevations induced by transcranial DC motor cortex stimulation in humans.Neurology. 2001; 57: 1899-1901
- Exploring prefrontal cortex functions in healthy humans by transcranial electrical stimulation.Neurosci Bull. 2015; 31: 198-206
- Polarization of the human motor cortex through the scalp.Neuroreport. 1998; 9: 2257-2260
- Applications of transcranial direct current stimulation for understanding brain function.Trends Neurosci. 2014; 37: 742-753
- Noninvasive transcranial direct current stimulation over the left prefrontal cortex facilitates cognitive flexibility in tool use.Cogn Neurosci. 2013; 4: 81-89
- Left lateralizing transcranial direct current stimulation improves reading efficiency.Brain Stimul. 2012; 5: 201-207
- Fast forward: supramarginal gyrus stimulation alters time measurement.J Cogn Neurosci. 2010; 22: 23-31
- Clinical research with transcranial direct current stimulation (tDCS): challenges and future directions.Brain Stimul. 2012; 5: 175-195
- Treatment of primary progressive aphasias by transcranial direct current stimulation combined with language training.J Alzheimers Dis. 2014; 39: 799-808
- Effects of transcranial direct current stimulation on language improvement and cortical activation in nonfluent variant primary progressive aphasia.Neurosci Lett. 2013; 549: 29-33
- Transcranial DC stimulation (tDCS): a tool for double-blind sham-controlled clinical studies in brain stimulation.Clin Neurophysiol. 2006; 117: 845-850
- Neurostimulation in Alzheimer's disease: from basic research to clinical applications.Neurol Sci. 2015; 36: 689-700
- Induction of neuroplasticity and recovery in post-stroke aphasia by non-invasive brain stimulation.Front Hum Neurosci. 2013; 7: 888
- Transcranial direct current stimulation in epilepsy.Brain Stimul. 2015; 8: 455-464
- Intracellular activities and evoked potential changes during polarization of motor cortex.J Neurophysiol. 1965; 28: 166-185
- The action of brief polarizing currents on the cerebral cortex of the rat (1) during current flow and (2) in the production of long-lasting after-effects.J Physiol. 1964; 172: 369-382
- Shaping the effects of transcranial direct current stimulation of the human motor cortex.J Neurophysiol. 2007; 97: 3109-3117
- Excitability modulation of the motor system induced by transcranial direct current stimulation: a multimodal approach.Neuroimage. 2013; 83: 569-580
- Excitability changes induced in the human primary visual cortex by transcranial direct current stimulation: direct electrophysiological evidence.Invest Ophthalmol Vis Sci. 2004; 45: 702-707
- Manipulation of phosphene thresholds by transcranial direct current stimulation in man.Exp Brain Res. 2003; 150: 375-378
- Partially non-linear stimulation intensity-dependent effects of direct current stimulation on motor cortex excitability in humans.J Physiol. 2013; 591: 1987-2000
- Comparing cortical plasticity induced by conventional and high-definition 4 x 1 ring tDCS: a neurophysiological study.Brain Stimul. 2013; 6: 644-648
- It's the thought that counts: examining the task-dependent effects of transcranial direct current stimulation on executive function.Brain Stimul. 2015; 8: 253-259
- Towards unravelling task-related modulations of neuroplastic changes induced in the human motor cortex.Eur J Neurosci. 2007; 26: 2687-2691
- tDCS polarity effects in motor and cognitive domains: a meta-analytical review.Exp Brain Res. 2012; 216: 1-10
- Polarity and timing-dependent effects of transcranial direct current stimulation in explicit motor learning.Neuropsychologia. 2011; 49: 800-804
- Effect of the nicotinic alpha4beta2-receptor partial agonist varenicline on non-invasive brain stimulation-induced neuroplasticity in the human motor cortex.Cereb Cortex. 2015; 25: 3249-3259
- Effect of serotonin on paired associative stimulation-induced plasticity in the human motor cortex.Neuropsychopharmacology. 2013; 38: 2260-2267
- Impact of 5-HTTLPR and BDNF polymorphisms on response to sertraline versus transcranial direct current stimulation: implications for the serotonergic system.Eur Neuropsychopharmacol. 2013; 23: 1530-1540
- Quantitative review finds No evidence of cognitive effects in healthy populations from single-session transcranial direct current stimulation (tDCS).Brain Stimul. 2015; 8: 535-550
- A re-evaluation of the cognitive effects from single-session transcranial direct current stimulation.Brain Stimul. 2015; 8: 663-665
- On the use of meta-analysis in neuromodulatory non-invasive brain stimulation.Brain Stimul. 2015; 8: 666-667
- Data synthesis in meta-analysis may conclude differently on cognitive effect from transcranial direct current stimulation.Brain Stimul. 2015; 8: 974-976
- Anodal transcranial direct current stimulation of the prefrontal cortex enhances complex verbal associative thought.J Cogn Neurosci. 2009; 21: 1980-1987
- Transcranial direct current stimulation improves word retrieval in healthy and nonfluent aphasic subjects.J Cogn Neurosci. 2011; 23: 2309-2323
- Effects of transcranial direct current stimulation (tDCS) on behaviour and electrophysiology of language production.Neuropsychologia. 2011; 49: 3989-3998
- Noninvasive brain stimulation improves language learning.J Cogn Neurosci. 2008; 20: 1415-1422
- Naming facilitation induced by transcranial direct current stimulation.Behav Brain Res. 2010; 208: 311-318
- Transcranial direct current stimulation over Broca's region improves phonemic and semantic fluency in healthy individuals.Neuroscience. 2011; 183: 64-70
- Altering automatic verbal processes with transcranial direct current stimulation.Front Psychiatry. 2012; 3: 73
- Electrical brain stimulation improves cognitive performance by modulating functional connectivity and task-specific activation.J Neurosci. 2012; 32: 1859-1866
- Electrode montage dependent effects of transcranial direct current stimulation on semantic fluency.Behav Brain Res. 2013; 248: 129-135
- Introduction to meta-analysis.John Wiley & Sons, Chichester, UK2009 (xxviii, p. 421)
- Statistical methods for meta-analysis.Academic Press, Orlando1985 (xxii, p. 369)
- Statistical power analysis for the behavioral sciences.2nd ed. L. Erlbaum Associates, Hillsdale, NJ1988 (xxi, p. 567)
- Cochrane handbook for systematic reviews of interventions.Cochrane book series. Wiley-Blackwell, Chichester, England; Hoboken, NJ2008 (xxi, p. 649)
- Conducting quantitative synthesis when comparing medical interventions: AHRQ and the Effective Health Care Program.J Clin Epidemiol. 2011; 64: 1187-1197
- Improving working memory: the effect of combining cognitive activity and anodal transcranial direct current stimulation to the left dorsolateral prefrontal cortex.Brain Stimul. 2011; 4: 84-89
- Enhanced motor learning following task-concurrent dual transcranial direct current stimulation.PLoS One. 2013; 8: e85693
- The interaction with task-induced activity is more important than polarization: a tDCS study.Brain Stimul. 2015; 8: 269-276
- Noninvasive cortical stimulation enhances motor skill acquisition over multiple days through an effect on consolidation.Proc Natl Acad Sci U S A. 2009; 106: 1590-1595
Article info
Publication history
Published online: June 26, 2015
Accepted:
June 22,
2015
Received in revised form:
June 19,
2015
Received:
April 16,
2015
Footnotes
This work was supported by funding from National Institutes of Health (AG017586 and 5T32AG000255).
Identification
Copyright
© 2015 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
