Emotional dysregulation such as that seen in depression, are a long-term consequence of mild traumatic brain injury (TBI), that can be improved by using neuromodulation treatments such as repetitive transcranial magnetic stimulation (rTMS). Previous studies provide insights into the changes in functional connectivity related to general emotional health after the application of rTMS procedures in patients with TBI. However, these studies provide little understanding of the underlying neuronal mechanisms that drive the improvement of the emotional health in these patients. The current study focuses on inferring the effective (causal) connectivity, after rTMS treatment of cognitive problems in TBI patients (N=32) with rTMS, and their association with emotional health. Specifically, we used resting state functional MRI (fMRI) together with spectral dynamic causal model (spDCM) to investigate changes in brain effective connectivity, before and after the application of rTMS. We investigated the effective connectivity of the cortico-limbic network comprised of 11 regions of interest (ROIs) which are part of the default mode, salience and executive control networks, known to be implicated in emotional processing. The results indicate that overall, the activity of all the regions reduced after the neuromodulation. The cardinal region in the analysis was dorsal anterior cingulate cortex (dACC) which is considered to be the most influenced during emotional health disorders. Our findings implicate the altered connectivity of dACC with left AI and mPFC, after the application of rTMS, as a potential neural mechanism underlying improvement of emotional health. Our investigation highlights the importance of these brain regions as treatment targets in emotional processing in TBI.
The MATLAB folder contains code files for fMRI preprocessing, spectral dynamic causal modelling application, parametric empirical bayes for group level analysis and for associativity analysis. Bash script folder contains the script for ICA-AROMA application on the dataset. The masks used for ROIs definition are in the folder named Masks.