The Impact of Transcranial Direct Current Stimulation (tDCS) on Memory Function in Older Adults with Mild Cognitive Impairment: A Systematic Review

Document Type : Systematic Review

Authors

1 Department of Review Studies, Basic Neuroscience Research Group, Tehran, Iran.

2 Department Cellular and Molecular Biology, Faculty of Basic Sciences, Islamic Azad University, Zarghan, Iran.

Abstract

Mild Cognitive Impairment (MCI) represents a transitional phase between normal aging and dementia, primarily affecting memory. It affects nearly one-fifth of adults over 50 worldwide, highlighting its growing clinical importance. Pharmacological treatments have shown limited efficacy, prompting interest in non-invasive interventions such as transcranial direct current stimulation (tDCS), which modulates cortical excitability through weak electrical currents. This systematic review aimed to evaluate the effects of tDCS on memory performance in older adults with MCI and to identify protocol-specific predictors of improvement. A systematic search was conducted in PubMed, Scopus, and Web of Science (up to April 2025) following PRISMA guidelines. Eligible studies included randomized and non-randomized trials examining tDCS alone or combined with cognitive training in adults aged 60 years and older with MCI. Ten studies (N = 428) met inclusion criteria. Due to heterogeneity, findings were synthesized narratively. Overall, tDCS significantly improved verbal and recognition memory, as well as spatial and episodic memory performance. Neurophysiological findings indicated enhanced neural activity and connectivity. Stimulation targeting the left dorsolateral prefrontal cortex produced the most consistent benefits, especially when applied for ten or more sessions at an intensity of 2 mA. Mild side effects, such as redness and tingling, occurred in approximately 20–30% of participants, with no serious adverse events reported. Preliminary evidence supports the effectiveness and safety of tDCS in improving memory among individuals with MCI. However, variability in protocols and small sample sizes underscore the need for standardized, biomarker-guided, and longitudinal research.

Keywords

Main Subjects

References

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Cognitive Science Research
Volume 1, Issue 3
October 2025
Pages 55-73

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History

  • Receive Date: 08 August 2025
  • Revise Date: 15 September 2025
  • Accept Date: 22 September 2025
  • First Publish Date: 22 September 2025
  • Publish Date: 01 October 2025

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