Concurrent single-pulse (sp) TMS/fMRI to reveal the causal connectome in healthy and patient populations

Abstract

Neuroimaging and cognitive neuroscience studies have identified neural circuits linked to anxiety, mood, and trauma-related symptoms and focused on their interaction with the medial prefrontal default mode circuitry. Despite these advances, developing new neuromodulatory treatments based on neurocircuitry remains challenging. It remains unclear which nodes within and controlling these circuits are affected and how their impairment is connected to psychiatric symptoms. Concurrent single-pulse (sp) TMS/fMRI offers a promising approach to probing and mapping the integrity of these circuits. In this study, we present concurrent sp-TMS/fMRI data along with structural MRI scans from 152 participants, including both healthy and depressed individuals. The sp-TMS was administered to 11 different cortical sites, providing a dataset that allows researchers to investigate how brain circuits are modulated by spTMS.

Keywords: PTSD; TMS/fMRI; resting state fMRI; single pulse TMS.

Fig 1:

(A) Recruitment Pipeline. Every participant undergoes a screening process and is then separated into one of 4 groups. (B) Imaging pipeline. (C) Gender balance per group for all reported participants. (D) Age per group (in years) for all reported participants.

Fig 2:

Project timeline and stimulation paradigm at different resolutions. (A) The study consists of 2 sessions, the first being MRI acquisition without TMS and the second including TMS. There were 11 TMS-fMRI runs, each corresponding to an identified cortical region from day 1. (B) The concurrent TMS-fMRI period lasts for ~167 effective TRs where an effective TR is 2400 ms. (C) 1 Effective TR = 2400 ms where 1 Actual TR = 2100 ms. A 300 ms gap is left in which stimulation may or may not occur. Stimulation occurs on a jittered 6-7 TR basis.

Fig 3:

Summary of the stimulation data. (A) Motor Threshold and Stimulation Percentage across all participants. (B) Stimulation sites. (C) Subjective Units of Distress Scale across all participants grouped by stimulation site. Horizontal bars highlight statistical significance (p<0.05) and are colored by stimulation sight.

Fig 4:

Image Quality Metrics. (A) Number of participants with data grouped by imaging/stimulation target. (B) A comparison of TSNR, SNR, and Mean FD across clinical groupings. The Dashed line represents the mean across groups. Horizontal bars highlight statistical significance. (C) A comparison of group level Image Quality Metrics as compared to the mriqc database deplete of outliers greater than 5 IRQs from mean. Horizontal bars highlight statistical significance.