Low-intensity focused ultrasound with continuous theta burst stimulation induces human primary motor cortex functional connectivity changes

Motivation: Combining low-intensity transcranial focused ultrasound stimulation (TUS) akin to continuous theta burst stimulation (cTBS) setting (ctbTUS) with cTBS over M1 can be a potential strengthening non-invasive neuromodulatory method. Goal(s): To understand the neuroplasticity in response to ctbTUS or simultaneous ctbTUS+cTBS. Approach: Resting-state fMRI with seed-based analysis with seeds of M1 and its first dorsal interosseous (FDI) muscle representation (M1FDI) was used to assess functional connectivity (FC) changes due to cTBS, ctbTUS, or ctbTUS+cTBS. Results: We replicated M1-FC degradations in ipsilateral sensorimotor regions due to cTBS, and verified the potential synergic effect of ctbTUS+cTBS on M1-FC decreases in supplementary motor area. Impact: Our study is the first to use resting-state fMRI to investigate FC changes within motor network due to either cTBS, ctbTUS, or ctbTUS+cTBS stimulations on left M1. The results help understand the potential of ctbTUS+cTBS to be a novel therapy.