The After-Effect of Accelerated Intermittent Theta Burst Stimulation at Different Session Intervals

Abstract

The study aims to investigate the after-effect of three sessions of intermittent theta-burst stimulation (iTBS) on motor cortical excitability. The iTBS was induced over the primary motor cortex (M1) at different time intervals. Methods: The study has a crossover design. Sixteen participants were assigned to three groups and received different accelerated iTBS (aiTBS) protocols during each visit: (1) three continuous sessions with no interval (iTBS18000); (2) three iTBS sessions with 10-min intervals (iTBS600 × 3 * 10); and (3) three iTBS sessions with 30-min intervals (iTBS600 × 3 * 30). As washout period, each visit is separated by at least 7 days. We measured the motor cortical excitability changes and intracortical inhibition. Results: A dose of 1,800 pulses of aiTBS per day is tolerable. The iTBS1800 led to a reduced cortical excitability; whereas iTBS600 × 3 * 10 and iTBS600 × 3 * 30 enhanced cortical excitability to a differential extent. After a total dose of 1,800 pulses, iTBS600 × 3 * 30 exhibited the longer effect and highest percentage of individuals with enhanced cortical excitability. Conclusion: The results suggest that aiTBS protocols at different time intervals result in different motor cortical excitability after-effects.

Enhancing neuronal plasticity through intracranial theta burst stimulation in the human sensorimotor cortex

“…However, iTBS treatments in animal models are delivered multiple times during hours, repeated over several days and at high amplitude currents. Recent human rTMS studies suggested that a single iTBS therapy session is insufficient and that multiple sessions might provide benefit [26,27]. Our findings indicate that multiple iTBS treatments do not result in linear increases in beta coherence in line with a recent study [25], suggesting more complex dynamics that likely are subject and activity-dependent [62].…”

“…A potential explanation of the heterogenous effects is that stimulation was applied across several different functional regions across patients. Additionally, the authors used intermittent alpha burst stimulation while the most efficient protocol to induce increases in neural excitability uses intermittent theta burst stimulation (iTBS, brief bursts of 50-100Hz pulses repeated at 5 Hz) [18,[22][23][24][25][26][27][28]).…”

Cortical Inhibition State-Dependent iTBS Induced Neural Plasticity

“…The peak-topeak amplitude of MEPs evoked by a suprathreshold stimulus with an intensity of 120% RMT was used to probe the excitability of the motor cortex. Before conducting iTBS, each participant received two sessions of single-pulse TMS with 20 consecutive pulses of each with an interval of 5 min at baseline to confirm intraindividual reliability of cortical excitability; the following trials could begin until the difference between average MEPs in two sessions of measurement was no more than 20% (Yu et al, 2020). To quantify the level of GABA or NMDA receptor-mediated activity before stimulation, we measured SICI, LICI, and ICF successively before conducting iTBS using a paired pulse paradigm at rest (Kujirai et al, 1993) (see Figure 1).…”

Preconditioning with Cathodal High-Definition Transcranial Direct Current Stimulation Sensitizes the Primary Motor Cortex to Subsequent Intermittent Theta Burst Stimulation

“…The peak-to-peak value was averaged as the baseline. Two baseline measurements were obtained (separated by 5 min) before any intervention in order to assure the intraindividual reliability of cortical excitability [ 20 ], and the plasticity protocol was applied if there was no more than a 10% difference between the 2 baseline values.…”