P 31 A multimodal approach to exploring TMS-induced changes to the fronto-striatal network

Background The fronto-striatal network is involved in various cognitive and emotional processes. Intermittent theta burst transcranial magnetic stimulation (TMS) has been shown to modulate functional connectivity (FC) of connected areas. We applied intermittent theta burst stimulation (iTBS) at sub- and supra-motor-threshold to modulate fronto-striatal resting-state functional connectivity. The aim was to explore the link between TMS-induced functional connectivity changes in the fronto-striatal network and structural connectivity. Methods Eleven healthy subjects underwent excitatory iTBS at two intensities (90% and 120% of individual resting motor threshold) on two separate days. 600 pulses (2s trains, 8s pauses, 3.33min) were applied over the left prefrontal cortex. A DTI (diffusion tensor imaging) scan and, a task-free resting state functional magnetic resonance imaging scan (directly before and 7min after stimulation) was conducted. Network analysis of the functional connectivity and diffusion tensor imaging data of the fronto-striatal and the limbic system was conducted and linked in a multimodal approach. Results Preliminary functional connectivity data shows that the connectivity pattern after the sub- and the supra-threshold TMS differ greatly. The sub-threshold stimulation increased fronto-striatal connectivity mainly in the left hemisphere, as well as intra-striatal and fronto-limbic connectivity spanning both hemispheres. Supra-threshold stimulation decreased connectivity mainly in the right hemisphere, i.e. between the frontal cortex and the caudate, as well as parts of the limbic system. The high-intensity stimulation caused an increase in connectivity between the caudate and the amygdala in the right hemisphere.