EEG Changes in Schizophrenia Following tDCS: A Systematic Scoping Review

Area of Science:

• Neuroscience
• Psychiatry
• Biomedical Engineering

Background:

• Transcranial direct current stimulation (tDCS) is explored as an adjunctive therapy for schizophrenia.
• Existing electroencephalography (EEG) studies on tDCS in schizophrenia yield inconsistent results.
• Clarifying tDCS effects on EEG variables is crucial for understanding its therapeutic potential.

Purpose of the Study:

• To systematically review and synthesize findings on tDCS effects on EEG variables in schizophrenia patients.
• To identify which EEG parameters are most consistently modulated by tDCS in this population.

Main Methods:

• A systematic scoping review adhering to PRISMA guidelines.
• Searched four major databases: PubMed, Cochrane Library, Web of Science, and ScienceDirect.
• Utilized the PIO framework (Population: schizophrenia; Intervention: tDCS; Outcome: any EEG variable).

Main Results:

• Twenty-five papers were included, yielding forty-two EEG variable occurrences.
• Event-related potentials (ERPs) constituted the majority of investigated variables (n=25).
• N100 potentials showed the highest response rate (80%), followed by gamma activity (67%) and MMN (60%).
• P300 potentials showed no significant response to tDCS across all studies.
• Most studies used 20 minutes of 2 mA stimulation in a bicephalic montage.

Conclusions:

• tDCS predominantly modulates sensory-auditory N100 potentials and pre-attentive MMN in schizophrenia.
• Higher-order cognitive potentials, such as P300, are not significantly affected by tDCS.
• The overall modulatory effects of tDCS on cognitive functions in schizophrenia remain unclear.