iTBS Methods and Motor Cortex Excitability

In a recent publication by Gamboa et al. 20108 it was shown that extended theta-burst stimulation duration might have reverse effects on cortical excitability when compared to the original Huang et al. 2005 publication. While the post treatment effects of the original Huang et al. 2005 protocol were successfully replicated, when continuous theta burst stimulation (cTBS) protocols were doubled to 1200 pulses over 80 seconds and the iTBS protocols were doubled to 1200 pulses over 390 seconds, there was increased facilitation after the prolonged cTBS and decreased excitability after prolonged iTBS. Currently there is an interest in optimizing repetitive transcranial magnetic stimulation (rTMS) protocols and in particular theta burst stimulation as both a therapeutic and an investigational tool. In Hanlon et al. 2015, a novel theta burst paradigm is described in which two trains of 1800 pulses of cTBS were administered, each train separated by a one-minute interval. In this study 11-cocaine dependent individuals underwent cTBS over the medial prefrontal cortex (MPFC) and showed attenuated craving as well as decreases in activity of the striatum and anterior insula. This study aims to replicate the findings of the Gamboa and Huang protocols as well as investigate how novel theta burst stimulation paradigms such as those described in Hanlon et al. 2015, which are currently being explored as therapeutic methods in addiction may change cortical excitability.