The effect of functional magnetic resonance imaging connectivity on resting motor threshold transcranial magnetic stimulation in schizophrenia participants

Schizophrenia is a neurological disorder known to influence the motor region. Transcranial magnetic stimulation (TMS) is a non-invasive neuromodulation technique being investigated as a treatment for schizophrenia. Resting motor threshold (RMT) is the dosage parameter for TMS treatment protocols and is known to vary between participants with limited understanding of the drivers of this variance. Previous investigations have used functional magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), and individual level neuroanatomy to explain RMT variability. Our previous investigation showed neuroanatomy influences RMT in both schizophrenia and healthy populations and this relationship was weakened by the presence of schizophrenia. In this study, 54 participants with schizophrenia-diagnosed, who were antipsychotic naive and 43 non-impaired controls underwent single pulse TMS, structural magnetic resonance imaging, and fMRI. An independent component analysis (ICA) was used to process fMRI data into 25 distinct channels where correlations were derived between channels. Linear and multiple regression models were used to evaluate first, the influence of these channel interactions on RMT followed by their influence when individual level neuroanatomy was also considered. We found that between-channel functional connectivity was altered in individuals with schizophrenia and that fMRI can contribute to prediction of RMT, but differently in both cohorts and to a lesser degree than individual level neuroanatomical measures. This suggests that functional connectivity influences TMS response and fMRI might help in dosage calculations of clinical TMS protocols.