Inter- and Intra-individual Variability Following Intermittent Theta Burst Stimulation: Implications for Rehabilitation and Recovery

Abstract Background The continued refinement of non-invasive brain stimulation (NBS) techniques is indicative of promising clinical and rehabilitative interventions that are able to modulate cortical excitability. Intermittent theta burst stimulation (iTBS) is one such technique that can increase cortical excitability, purportedly via LTP-like mechanisms. While iTBS may have the capacity to promote recovery after neurological injury, and to combat cognitive and motor decline, recent reports observed highly variable effects across individuals, questioning the efficacy of iTBS as a clinical tool. Objective The aim of this study was to examine intra-individual reliability and inter-individual variability in responses to iTBS. Methods Thirty healthy participants completed two experimental sessions of the iTBS protocol 1–3 weeks apart. Motor evoked potentials in response to single pulse TMS were used to assess corticospinal excitability prior to, and up to 36 min following, iTBS. Results At the group level, iTBS evoked statistically significant increases in motor cortical excitability across both sessions ( P