Changes in cortico-spinal excitability by individualized quadri-pulse theta burst stimulation

Abstract Introduction: In many neurodevelopmental disorders impaired synaptic plasticity is believed to be a key pathophysiological mechanism. It can studied through transcranial magnetic stimulation (TMS). TMS over the primary motor cortex (M1) triggers oscillations called I-waves that show three maxima (I1-I3). seem important in mechanisms. Hence targeting directly might increase effects of inducing TMS-protocols like quadri-pulse theta burst (qTBS). The aim this study was investigate whether an individualized qTBS (i-qTBS), adapted personal I-wave latencies applicated posterior-anterior (PA) and anterior-posterior (AP) current flow direction brain, could induce plasticity. Methods: 20 (22-34 years old, f = 16) healthy adults participated sessions. First, we measured PA AP direction. Short interval intracortical facilitation with interstimulus intervals (ISI) 0.1 6 ms were applied steps ms. following sessions i-qTBS applied, respectively, using custommade stimulator. consisted 1440 full-sine pulses delivered continuously at M1, bursts four separated by individually determined ISIs based on latencies. We evoked potentials (MEP) before 5, 15, 30 60 min after i-qTBS. Results: MEP amplitudes significantly increased both directions all time points started rising 15 minutes. There no significant difference between directions. Conclusions: I-qTBS M1 induced corticospinal excitability directions, indicating induction This finding opposed our previous results fixed ISI bidirectional may underline role humans, possibly offering new treatment options. Research Category Technology Methods Basic Research: 10. Transcranial Magnetic Stimulation (TMS) Keywords: stimulation, excitability, neuronal plasticity,