A Checklist for Assessing the Methodological Quality of Concurrent tES-fMRI Studies (ContES Checklist): A Consensus Study and Statement

Abstract Background Low intensity transcranial electrical stimulation (tES), including alternating or direct current stimulation (tACS or tDCS), applies weak electrical stimulation to modulate brain circuits. Integration of tES with concurrent functional magnetic resonance imaging (fMRI) allows neuromodulation of brain regions while mapping network functions, therefore supporting causal studies of both brain function and tES effects. The methodology of tES-fMRI studies, including hardware and protocols, underpin any outcomes - so reporting methods in appropriate detail is required for reproducible experimental protocols. Despite the growing number of published reports, consensus-based checklists for disclosing standards of methodological details for concurrent tES-fMRI studies were not previously established. Objective To develop a consensus-based checklist of reporting standards for concurrent tES-fMRI studies to support methodological rigor, transparency, and reproducibility (ContES Checklist). Methods A two-phase Delphi consensus process was conducted by a steering committee (SC) of 13 members and 49 expert panelists (EP) through the International Network of the tES-fMRI (INTF) Consortium. The process began with a preliminary checklist including essential items and additional recommendations developed by the SC based on a systematic review of 57 concurrent tES-fMRI studies published before January 1, 2020. In the revision phase, contributors were invited to comment, revise, or add items/recommendations to the initial checklist. Then, in the rating phase, contributors were asked to evaluate the importance of the 17 essential items and 42 additional recommendations in the final checklist. Furthermore, the state of methodological transparency and reproducibility within the 57 collected concurrent tES-fMRI studies was assessed with the proposed checklist. Results During the revision and rating phases, the EP and SC refined the checklist based on a pre-registered consensus framework and agreed upon essential items and additional recommendations, which involved three categories: (1) technological factors, (2) safety and noise tests, and (3) methodological factors. The level of adherence to the checklist varied among the 57 published concurrent tES-fMRI articles, ranging from 24% to 76%. On average, 53% of the checklist items were reported in a given article. Conclusions It is expected that the use of the ContES checklist will enhance the methodological reporting quality of future concurrent tES-fMRI studies and thus increase methodological transparency and reproducibility.