Inter- and Intra-individual variability following intermittent theta burst stimulation: implications for rehabilitation and recovery

Mark R Hinder; Emily L Goss; Hakuei Fujiyama; Alison J Canty; Michael I Garry; Jennifer Rodger; Jeffery J Summers

doi:10.1016/j.brs.2014.01.004

Inter- and Intra-individual variability following intermittent theta burst stimulation: implications for rehabilitation and recovery

Brain Stimul. 2014 May-Jun;7(3):365-71. doi: 10.1016/j.brs.2014.01.004. Epub 2014 Jan 9.

Authors

Mark R Hinder¹, Emily L Goss², Hakuei Fujiyama³, Alison J Canty⁴, Michael I Garry², Jennifer Rodger⁵, Jeffery J Summers⁶

Affiliations

¹ Human Motor Control Laboratory, School of Medicine, University of Tasmania, Private Bag 30, Hobart, Tasmania 7001, Australia. Electronic address: Mark.Hinder@utas.edu.au.
² Human Motor Control Laboratory, School of Medicine, University of Tasmania, Private Bag 30, Hobart, Tasmania 7001, Australia.
³ Human Motor Control Laboratory, School of Medicine, University of Tasmania, Private Bag 30, Hobart, Tasmania 7001, Australia; Movement Control and Neuroplasticity Research Group, Department of Kinesiology, KU Leuven, Belgium.
⁴ School of Medicine, University of Tasmania, Australia.
⁵ Experimental and Regenerative Neuroscience, School of Animal Biology, University of Western Australia, Australia.
⁶ Human Motor Control Laboratory, School of Medicine, University of Tasmania, Private Bag 30, Hobart, Tasmania 7001, Australia; Research Institute for Exercise and Sport Sciences, Liverpool John Moores University, UK.

PMID: 24507574
DOI: 10.1016/j.brs.2014.01.004

Abstract

Background: The continued refinement of non-invasive brain stimulation (NBS) techniques is indicative of promising clinical and rehabilitative interventions that are able to modulate cortical excitability. Intermittent theta burst stimulation (iTBS) is one such technique that can increase cortical excitability, purportedly via LTP-like mechanisms. While iTBS may have the capacity to promote recovery after neurological injury, and to combat cognitive and motor decline, recent reports observed highly variable effects across individuals, questioning the efficacy of iTBS as a clinical tool.

Objective: The aim of this study was to examine intra-individual reliability and inter-individual variability in responses to iTBS.

Methods: Thirty healthy participants completed two experimental sessions of the iTBS protocol 1-3 weeks apart. Motor evoked potentials in response to single pulse TMS were used to assess corticospinal excitability prior to, and up to 36 min following, iTBS.

Results: At the group level, iTBS evoked statistically significant increases in motor cortical excitability across both sessions (P < 0.001), with 22 out of 30 participants exhibiting increases in excitability in both sessions. A strong intraclass correlation demonstrated that both the direction, and magnitude of the plastic changes were reliable at the individual level.

Conclusions: Overall, our results suggest that iTBS is capable of inducing relatively robust and consistent effects within and between young individuals. As such, the capacity for iTBS to be exploited in clinical and rehabilitative interventions should continue to be explored.

Keywords: Cortical plasticity; Inter- and intra-individual variability; TMS; Theta burst stimulation.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adolescent
Adult
Brain / pathology*
Brain Mapping / methods*
Electromyography
Evoked Potentials, Motor / physiology
Female
Healthy Volunteers
Humans
Male
Motor Cortex / pathology
Motor Cortex / physiology
Neuronal Plasticity / physiology
Regression Analysis
Rehabilitation
Reproducibility of Results
Theta Rhythm / physiology*
Transcranial Magnetic Stimulation / methods*
Young Adult