Fig. 1.

Cortical reactivity and plasticity can be measured noninvasively in the human motor cortex using TMS. Reactivity refers to the average amplitude of MEPs elicited by single-pulse TMS, while plasticity is defined as the change in reactivity induced by iTBS. A) MR-guided TMS was applied to the left primary motor cortex and resulting MEPs were recorded from the right FDI muscle by surface EMG. B). The present study assessed TMS-iTBS measures of plasticity as well as paired pulse TMS measures of cortical inhibition and facilitation. After determining resting motor threshold (rMT), 50 single (unconditioned) monophasic TMS pulses were delivered, followed by three sets of 50 pulse-pairs to assess short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), and long-interval intracortical inhibition (LICI). After a break, rMT was reassessed and three sets of 30 biphasic pulses were delivered to measure baseline cortico-motor reactivity. The active motor threshold (aMT) was assessed and iTBS was applied. Cortico-motor reactivity was reassessed in six blocks of 30 pulses at 5, 10, 20, 30, 40, and 50 min post-iTBS. C) Example MEP traces from a single control subject (top) and T2DM patient (bottom) recorded at baseline (left) and 10 min after iTBS (right).