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. 2015 Dec;22(Spec Issue):36-44.

Theta-burst Transcranial Magnetic Stimulation Alters the Functional Topography of the Cortical Motor Network

Nor Azila Noh  1 , Giorgio Fuggetta  2 , Paolo Manganotti  3
Affiliations

Theta-burst Transcranial Magnetic Stimulation Alters the Functional Topography of the Cortical Motor Network

Nor Azila Noh et al. Malays J Med Sci. 2015 Dec.

Abstract

Background: Transcranial magnetic stimulation (TMS) is a non-invasive tool that is able to modulate the electrical activity of the brain depending upon its protocol of stimulation. Theta burst stimulation (TBS) is a high-frequency TMS protocol that is able to induce prolonged plasticity changes in the brain. The induction of plasticity-like effects by TBS is useful in both experimental and therapeutic settings; however, the underlying neural mechanisms of this modulation remain unclear. The aim of this study was to investigate the effects of continuous TBS (cTBS) on the intrahemispheric and interhemispheric functional connectivity of the resting and active brain.

Methods: A total of 26 healthy humans were randomly divided into two groups that received either real cTBS or sham (control) over the left primary motor cortex. Surface electroencephalogram (EEG) was used to quantify the changes of neural oscillations after cTBS at rest and after a choice reaction time test. The cTBS-induced EEG oscillations were computed using spectral analysis of event-related coherence (ERCoh) of theta (4-7.5 Hz), low alpha (8-9.5 Hz), high alpha (10-12.5 Hz), low beta (13-19.5 Hz), and high beta (20-30 Hz) brain rhythms.

Results: We observed a global decrease in functional connectivity of the brain in the cTBS group when compared to sham in the low beta brain rhythm at rest and high beta brain rhythm during the active state. In particular, EEG spectral analysis revealed that high-frequency beta, a cortically generated brain rhythm, was the most sensitive band that was modulated by cTBS.

Conclusion: Overall, our findings suggest that cTBS, a TMS protocol that mimics the mechanism of long-term depression of synaptic plasticity, modulates motor network oscillations primarily at the cortical level and might interfere with cortical information coding.

Keywords: electroencephalogram; long-term depression; motor cortex; neuromodulation; neuroplasticity.

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Figures

Figure 1
Figure 1
ERCoh low β as a function of Group and pairs of electrodes. The figure illustrates EEG synchronisation of C3-Fz, C3-Cz, C3-P3, C3-Pz, and C3-P4 pairs of electrodes for real cTBS compared to sham at rest. *significant real cTBS rest vs sham (P < 0.05; Bonferroni corrected; n = 26).
Figure 2
Figure 2
ERCoh low β as a function of Group, Block and pairs of electrodes. The figure illustrates EEG synchronisation of several frontal-central-parietal pairs of electrodes for real cTBS compared to sham at rest across the three blocks of time. *significant real cTBS rest vs sham (P < 0.05; Bonferroni corrected; n = 26).
Figure 3
Figure 3
ERCoh high β as a function of Group and pairs of electrodes. The figure illustrates EEG synchronisation of C3-Cz, C3-C4, C3-P3, C3-Pz, and C3-P4 pairs of electrodes for real cTBS compared to sham during the active motor task. *significant real cTBS rest vs. sham (P < 0 .05; Bonferroni corrected; n = 26).
Figure 4
Figure 4
ERCoh high β as a function of Group, Block and pairs of electrodes. The figure illustrates EEG synchronisation of the central-parietal pairs of electrodes for real cTBS compared to sham across the three blocks during the active motor task. *significant real cTBS rest vs. sham (P < 0 .05; Bonferroni corrected; n = 26).
See this image and copyright information in PMC

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