ReviewEfficacy and Time Course of Theta Burst Stimulation in Healthy Humans

-Magnitude and time course of sixty-four theta burst stimulation studies were reviewed.-Intermittent theta burst stimulation potentiates the cortex up to 60 min.-If applied for 40 s continuous theta burst stimulation depresses the cortex up to 50 min.-If applied for 20 s continuous theta burst stimulation depresses the cortex up to 20 min.-Results offer normative data for future theta burst stimulation studies on normal and abnormal cortical plasticity.

BackgroundIn the past decade research has shown that continuous (cTBS) and intermittent theta burst stimulation (iTBS) alter neuronal excitability levels in the primary motor cortex.ObjectiveQuantitatively review the magnitude and time course on cortical excitability of cTBS and iTBS.MethodsSixty-four TBS studies published between January 2005 and October 2014 were retrieved from the scientific search engine PubMED and included for analyses. The main inclusion criteria involved stimulation of the primary motor cortex in healthy volunteers with no motor practice prior to intervention and motor evoked potentials as primary outcome measure.ResultsITBS applied for 190 s significantly increases cortical excitability up to 60 min with a mean maximum potentiation of 35.54 ± 3.32%. CTBS applied for 40 s decreases cortical excitability up to 50 min with a mean maximum depression of −22.81 ± 2.86%, while cTBS applied for 20 s decreases cortical excitability (mean maximum −27.84 ± 4.15%) for 20 min.ConclusionThe present findings offer normative insights into the magnitude and time course of TBS-induced changes in cortical excitability levels.