The application of spaced theta burst protocols induces long‐lasting neuroplastic changes in the human motor cortex

Abstract

There is some limited evidence suggesting that the spaced application of repetitive transcranial magnetic stimulation (rTMS) protocols may extend the duration of induced neuroplastic changes. However, this has yet to be demonstrated in the human primary motor cortex (M1). We evaluated whether the paired application of an inhibitory rTMS protocol [continuous theta burst stimulation (cTBS)] at 10-min intervals prolonged the duration of induced M1 plasticity. Motor evoked potentials (MEPs) were recorded from the right first dorsal interosseous muscle before and following single and paired cTBS protocols applied with two intensities: 80% of active motor threshold (AMT 80 ) and 70% of resting motor threshold (RMT 70 ). Single cTBS protocols did not significantly influence MEP amplitudes. Whereas paired trains applied at AMT 80 had no effect on MEP amplitudes, paired cTBS trains at RMT 70 significantly reduced them. MEP amplitudes remained suppressed for at least 2 h following the second train. Control experiments suggested that the contraction used to establish active motor threshold prior to cTBS application may be responsible for blocking the effect of paired cTBS trains at AMT 80 . The results suggest that the spaced application of cTBS protocols may be an effective approach for establishing long-lasting M1 neuroplasticity only in the absence of prior voluntary motor activation. These findings may have important implications for the therapeutic application of rTMS.

Non-invasive induction of plasticity in the human cortex: Uses and limitations

“…Consistent with this, we have recently shown in humans that two inhibitory (cTBS) NIBS paradigms applied 10 minutes apart result in a plastic response that is less variable and longer lasting than that seen with a single application (Goldsworthy, Pitcher, & Ridding, 2012). As described above, there is evidence that such approaches can lead to significant and enduring behavioural effects (D. Cazzoli et al, 2012;T.…”

Inter- and intra-subject variability of motor cortex plasticity following continuous theta-burst stimulation

“…All sessions were conducted in the afternoon to minimise time-of-day influences (Sale et al 2007) and sessions were separated by ≥2 days (Goldsworthy et al 2012b;Hamada et al 2013;). …”

“…While many studies report significant changes in corticospinal excitability following application of rTMS (e.g. Di Lazzaro et al 2011;Huang et al 2007;Huang et al 2005;Stefan et al 2000) a number of others do not (Clow et al 2014;Goldsworthy et al 2012a;Hamada et al 2013;McAllister et al 2013;McAllister et al 2011), highlighting that the response to rTMS is rather variable. Large inter-and intra-subject NIBS response variability is a limiting factor in both basic and applied research .…”

Probing changes in corticospinal excitability following theta burst stimulation of the human primary motor cortex

“…For cTBS (Experiment 1), this pattern of stimuli was applied as a continuous 40-s train, whereas for iTBS (Experiment 2), bursts of stimuli were applied for 2 s at 10-s intervals for a total duration of 190 s (Huang et al, 2005). Stimulation intensity was set to 70% of RMT (Gentner et al, 2008;Goldsworthy et al, 2014a;Goldsworthy et al, 2012a), which was assessed just prior to TBS application using the same coil and biphasic pulse waveform.…”