Reproducibility of the effects of theta burst stimulation on motor cortical plasticity in healthy participants.
OBJECTIVE
Theta-burst stimulation (TBS) is a repetitive transcranial magnetic stimulation (TMS) protocol, capable of enhancing or suppressing the amplitude of contralateral motor-evoked potentials (MEP) for several minutes after stimulation over the primary motor cortex. Continuous TBS (cTBS) produces a long-term depression (LTD)-like reduction of cortical excitability. The purpose of this study was to assess the test-retest reproducibility of the effects of cTBS and to investigate which neurophysiologic markers of cTBS-induced plasticity are most reproducible.


METHODS
In ten healthy participants we evaluated in two different sessions the effects of cTBS (using AP-PA current direction, opposite to most commercial rTMS stimulators) on MEPs induced by single-pulse suprathreshold TMS (using AP-PA or PA current direction) over left motor cortex in the first dorsal interosseus (FDI) muscle.


RESULTS
Results demonstrate that the marker of cTBS induced-plasticity with highest within-subject reproducibility is the modulation of corticospinal excitability measured 5min after cTBS.


CONCLUSIONS
Overall the effects of cTBS modulation show limited test-retest reproducibility and some measures of the cTBS effects are more reproducible than others.


CONCLUSIONS
Studies comparing cTBS effects in healthy subjects and patients need to proceed with care. Further characterization of the effects of TBS and identification of the best metrics warrant future studies.
Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue KS-158, Boston MA 02215, USA.
Marine
M
Vernet
Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue KS-158, Boston MA 02215, USA.
Shahid
S
Bashir
Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue KS-158, Boston MA 02215, USA.
Woo-Kyoung
WK
Yoo
Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue KS-158, Boston MA 02215, USA.
Lindsay
L
Oberman
Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue KS-158, Boston MA 02215, USA.
Ilan
I
Mizrahi
Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue KS-158, Boston MA 02215, USA.
Frederick
F
Ifert-Miller
Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue KS-158, Boston MA 02215, USA.
Charles J
CJ
Beck
Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue KS-158, Boston MA 02215, USA; Institut Universitari de Neurorehabilitació Guttmann, Universidad Autónoma de Barcelona, Barcelona, Spain. Electronic address: apleone@bidmc.harvard.edu.
Alvaro
A
Pascual-Leone
D000328:Adult; D000368:Aged; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
Neurophysiological markers; Primary motor cortex; Transcranial magnetic stimulation; Variability