Translation of network mapping findings into therapeutic targets for transcranial magnetic stimulation

Abstract

Transcranial magnetic stimulation (TMS) has been used to effectively treat certain brain disorders, such as major depressive disorder, and holds great promise for other neurological and psychiatric symptoms. However, despite the increase in the number of trials conducted, the discovery of novel clinical applications of TMS has been limited. A key limiting factor is the absence of a priori methods capable of reliably localising symptom-specific targets in the brain that will respond to TMS. Network mapping methods have taken a different approach to prior neuroimaging techniques by mapping the structural or functional connections of brain abnormalities (e.g. locations of causal lesions or brain atrophy) to identify brain networks commonly connected to these focal abnormalities. Retrospective analyses have demonstrated overlap with current targets for clinical neuromodulation, and recently, studies have begun to prospectively target these networks with TMS. However, the translation of network mapping findings to TMS trials is not straightforward. The present review discusses how researchers can use the information provided by network mapping to help translate these findings to TMS trials, with an emphasis on target localisation. We first summarise the evidence for network mapping to identify targets for TMS, and then offer pragmatic guidance on target selection based on the on the nature of the network mapping results, feasibility and tolerability of TMS to the target, and considering the TMS electric field distribution in the brain. Overall, this review facilitates the translation of network mapping findings into novel targets for TMS trials in a range of brain disorders.