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Low-intensity transcranial electrical stimulation (tES), including alternating or direct current stimulation, applies weak electrical stimulation to modulate the activity of brain circuits. Integration of tES with concurrent functional MRI (fMRI) allows for the mapping of neural activity during neuromodulation, supporting causal studies of both brain function and tES effects. Methodological aspects of tES-fMRI studies underpin the results, and reporting them in appropriate detail is required for reproducibility and interpretability. Despite the growing number of published reports, there are no consensus-based checklists for disclosing methodological details of concurrent tES-fMRI studies. The objective of this work was to develop a consensus-based checklist of reporting standards for concurrent tES-fMRI studies to support methodological rigor, transparency and reproducibility (ContES checklist). A two-phase Delphi consensus process was conducted by a steering committee (SC) of 13 members and 49 expert panelists through the International Network of the tES-fMRI Consortium. The process began with a circulation of a preliminary checklist of essential items and additional recommendations, developed by the SC on the basis of a systematic review of 57 concurrent tES-fMRI studies. Contributors were then invited to suggest revisions or additions to the initial checklist. After the revision phase, contributors rated the importance of the 17 essential items and 42 additional recommendations in the final checklist. The state of methodological transparency within the 57 reviewed concurrent tES-fMRI studies was then assessed by using the checklist. Experts refined the checklist through the revision and rating phases, leading to a checklist with three categories of essential items and additional recommendations: (i) technological factors, (ii) safety and noise tests and (iii) methodological factors. The level of reporting of checklist items varied among the 57 concurrent tES-fMRI papers, ranging from 24% to 76%. On average, 53% of checklist items were reported in a given article. In conclusion, use of the ContES checklist is expected to enhance the methodological reporting quality of future concurrent tES-fMRI studies and increase methodological transparency and reproducibility.

Transcranial magnetic stimulation is used for a wide range of applications in cognitive, clinical, and neuroscience. However, the precise physiological mechanisms by which TMS influences brain function are only partially understood. Combining TMS with functional magnetic resonance imaging (fMRI) provides a more complete picture of the neural underpinnings of TMS effects. This article gives an overview of methodology and technical aspects concerned with combining TMS with fMRI. Furthermore, it explains the challenges involved with the combination of TMS with fMRI and proposes solutions to the same. It also focuses on recent applications of concurrent TMS-fMRI. Combining TMS with fMRI may allow a new noninvasive probe technique for the human brain. TMS-fMRI can be used to compare TMS-evoked effective connectivity in health and disease. It can potentially be used to investigate connectivity changes during different states, with different degrees of involvement for interconnected brain regions during different tasks.

BackgroundLow 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.ObjectiveTo develop a consensus-based checklist of reporting standards for concurrent tES-fMRI studies to support methodological rigor, transparency, and reproducibility (ContES Checklist).MethodsA 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.ResultsDuring 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.ConclusionsIt 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.