White matter matters: The role of structural brain connections in the response to transcranial magnetic stimulation

Even though repetitive transcranial magnetic stimulation (rTMS) is a promising non-invasive treatment option for a variety of neurological and psychiatric disorders, overall, the response rates are rather modest. It is hypothesized that the inter-individual variability in clinical responses could be related to the use of too general stimulation protocols applicable to broad patient populations. Optimal stimulation protocols might be subject-specific because of the individual brain connections. Diffusion MRI (dMRI) is a brain imaging technique able to map the structural connections within the white matter in detail. This junior postdoc research proposal focuses on the potential of dMRI data to gain more insight into the mechanisms of action of TMS in neuropsychiatric illnesses and to subsequently increase clinical efficacy using individualized stimulation protocols. Firstly, the potential of dMRI data to predict the clinical responses to rTMS protocols in depressed subjects will be investigated. Secondly, a pilot study in healthy volunteers will be conducted in which the fundamentals of TMS - in terms of effective TMS-induced electric fields and propagation of the effects via structural connections - can be investigated. The added knowledge from these projects can be translated into the prospective use of more personalized stimulation protocols; e.g. optimized coil positioning, taking into account the subject’s individual structural connections as derived from the dMRI data.