Efficacy and Time Course of Theta Burst Stimulation in Healthy Humans

Abstract

Background: In the past decade research has shown that continuous (cTBS) and intermittent theta burst stimulation (iTBS) alter neuronal excitability levels in the primary motor cortex.

Objective: Quantitatively review the magnitude and time course on cortical excitability of cTBS and iTBS.

Methods: Sixty-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.

Results: ITBS 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.

Conclusion: The present findings offer normative insights into the magnitude and time course of TBS-induced changes in cortical excitability levels.

Keywords: Cortical excitability; Cortical plasticity; Long-term depression; Long-term potentiation; Primary motor cortex; Theta burst stimulation.