Transcranial direct-current stimulation of the prefrontal cortex enhances working memory and suppresses pathological gamma power elevation in schizophrenia

ABSTRACT

Background

This investigation examines the clinical benefits of prefrontal cortex transcranial direct current stimulation (tDCS) treatment of working memory (WM) dysfunction in chronic schizophrenia patients.

Research design and methods

34 schizophrenia (SZ) patients were evaluated at baseline, and 29 patients were randomly assigned to either active tDCS intervention or sham tDCS intervention. tDCS intervention applied 10 consecutive sessions (20 minutes, 2 mA, two sessions a day) over 5 days. WM performance (N = 25), symptom severity (N = 29), and resting EEG (N = 17) were assessed from pre- to post-tDCS intervention. Additionally, symptom severity was noted over a 12-week follow-up period.

Results

WM accuracy significantly improved in the active tDCS group while WM accuracy in the sham tDCS group was unchanged. Significant symptom-severity reduction was sustained for one week after active tDCS intervention. Sustained resting gamma stability (RGS) was noted from baseline to post tDCS in the active-treatment group versus a significant elevation in pathological gamma power in the sham-tDCS group.

Conclusions

Examining treatment effects on RGS in SZ could be critical in identifying effective novel treatment strategies that promote left-DLPFC excitability and enhance WM functioning. Further empirical support is warranted to support the clinical benefits over longer periods of time.

Trial Registration

ClinicalTrials.gov Identifier: NCT04637724.

Ethics Approval Registration No

337–19

KEYWORDS:

• Dorsolateral prefrontal cortex (DLPFC)
• working memory (WM)
• neural oscillations
• resting gamma power
• neuromodulation

Author contributions

O Meiron was involved in conception, design, interpretation, reviewing and final approval of version to be published. A Yaniv was involved in acquisition and analysis of data. S Rozenberg was involved in the acquisition of data and data interpretation. J David was involved in acquisition of data and data analysis. All authors were involved in drafting the work. All authors agree to be accountable for all aspects of the work.

Declaration of interest

The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/14737175.2023.2294150

Additional information

Funding

The authors acknowledge funding through a grant from the Brain and Behavior Research Foundation (via grant no. 25689) awarded to OM.