"Conventional high frequency repetitive TMS paradigms, such as those used in the ... trial (O'Reardon et al., 2007), deliver 3000 pulses of 10 Hz stimulation over the course of 37.5 min. An alternative approach is theta-burst stimulation (TBS), in which a three-pulse 50-Hz burst is applied at 5 Hz. In intermittent TBS, a 2-s train of TBS is delivered every 10 s for ∼190 s (600 pulses in total). Intermittent TBS induces a form of plasticity that resembles long-term potentiation (Huang et al., 2005), changes to which are increasingly implicated in the pathophysiology of major depressive disorder (Player et al., 2013). Huang et al. (2005) demonstrated that application of intermittent TBS to motor cortex produced a consistent increase in the TMS-induced motor evoked potential (MEP) compared to baseline: an increase that could be considered a marker of cortical plasticity. By contrast, continuous TBS, which involves a continuous 40 s train of TBS to give a total of 600 pulses, produced a decrease in the TMS-induced MEP compared to baseline; a change that may be a marker of long-term depression (Huang et al., 2005)."

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Citation: (2014). Theta-burst transcranial magnetic stimulation in depression: when less may be more. Brain : a journal of neurology, 137(Pt 7), 1860-2.