The inconsistent effects of tDCS in rehabilitation and cognitive enhancement: sources of variability and paths to personalization

Background/aims: Transcranial direct current stimulation (tDCS) has emerged as a promising intervention in both rehabilitation and cognitive enhancement, yet its effects remain inconsistent across studies. This variability has raised questions about the underlying mechanisms influencing tDCS efficacy. Methods: In this review, we address the issue of the inconsistent effect of tDCS on motor and cognitive domains across studies in healthy individuals and those with neurodegenerative disorders. A review of literature in the field was conducted using PubMed and Google Scholar. Results: Research indicates that individual anatomical differences among subjects may contribute to the inconsistent outcomes observed, as variations in current density at targeted brain regions and genetic variations responsible for the stimulation effect. Understanding the factors that contribute to the inconsistent effects of tDCS will be essential for enhancing its application in clinical settings and maximizing its potential benefits in cognitive rehabilitation and enhancement. Conclusion: Future research should focus on optimizing tDCS parameters and exploring individualized approaches to treatment, taking into account the diverse responses observed in different populations.