Concurrent TMS/fMRI reveals individual DLPFC dose-response pattern

Martin Tik; Maria Vasileiadi; Michael Woletz; David Linhardt; Anna-Lisa Schuler; Nolan Williams; Christian Windischberger

doi:10.1016/j.neuroimage.2023.120394

Concurrent TMS/fMRI reveals individual DLPFC dose-response pattern

Neuroimage. 2023 Nov 15:282:120394. doi: 10.1016/j.neuroimage.2023.120394. Epub 2023 Oct 5.

Authors

Martin Tik¹, Maria Vasileiadi², Michael Woletz², David Linhardt², Anna-Lisa Schuler², Nolan Williams³, Christian Windischberger⁴

Affiliations

¹ MR Center of Excellence, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Lazarettgasse 14, Vienna 1090, Austria; Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Palo Alto, CA, USA.
² MR Center of Excellence, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Lazarettgasse 14, Vienna 1090, Austria.
³ Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Palo Alto, CA, USA.
⁴ MR Center of Excellence, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Lazarettgasse 14, Vienna 1090, Austria. Electronic address: christian.windischberger@meduniwien.ac.at.

PMID: 37805020
DOI: 10.1016/j.neuroimage.2023.120394

Abstract

Background: TMS is a valuable tool in both research and clinical settings, playing a crucial role in understanding brain-behavior relationships and providing treatment for various neurological and psychiatric conditions. Importantly, TMS over left DLPFC is an FDA approved treatment for MDD. Despite its potential, response variability to TMS remains a challenge, with stimulation parameters, particularly the stimulation intensity, being a primary contributor to these differences.

Objective: The objective of this study was to establish dose-response relationships of TMS stimulation in DLPFC by means of concurrent TMS/fMRI.

Methods: Here, we stimulated 15 subjects at different stimulation intensities of 80, 90, 100 and 110 % relative to the motor threshold during concurrent TMS/fMRI. The experiment comprised two sessions: one session to collect anatomical data in order to perform neuronavigation and one session dedicated to dose-response mapping. We calculated GLMs for each intensity level and each subject, as well as at a group-level per intensity.

Results: On a group level, we show that the strongest BOLD-response was at 100 % stimulation. However, investigating individual dose response-relationships showed differences in response patterns across the group: subjects that responded to subthreshold stimulation, subjects that required above threshold stimulation in order to show a significant BOLD-response and atypical responders.

Conclusions: We observed qualitative inter-subject variability in terms of dose-response relationship to TMS over left DLPFC, which hints towards the motor threshold not being directly transferable to the excitability of the DLPFC. Concurrent TMS/fMRI might have the potential to improve response rates to rTMS applications. As such, it may be valuable in the future to consider implementing this approach prior to clinical TMS or validating more cost-effective methods to determine dose and target with respect to changes in clinical symptoms.

Keywords: Dose response; Excitability; TMS-fMRI; Threshold; Transcranial magnetic stimulation.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Brain / physiology
Brain Mapping / methods
Dorsolateral Prefrontal Cortex*
Humans
Magnetic Resonance Imaging* / methods
Prefrontal Cortex / physiology
Transcranial Magnetic Stimulation / methods