Brain-State Dependent Stimulation in Human Motor Cortex for Plasticity Induction Using EEG-TMS

Abstract

Non-invasive motor cortex stimulation may result in long-term potentiation (LTP)-like plasticity of corticospinal excitability, and this may be useful to support neurorehabilitation after lesion, such as in stroke. However, the reported plasticity effects show large interindividual variability, and even intraindividual reliability is moderate at best. One possible strategy to improve size effect and consistency is to couple pulsed transcranial magnetic stimulation (TMS) to the endogenous brain state. We show here that instantaneous brain states measured with EEG have significant impact on TMS-induced corticospinal excitability. Consistent stimulation on the negative peak of the ongoing µ-rhythm results in LTP-like plasticity in 21/23 subjects, while stimulation at the positive peak had no effect. Findings raise the intriguing possibility that real-time information of instantaneous brain state can be utilized to control efficacy of plasticity induction in humans, and this may be utilized in clinical settings to support therapeutic reorganization of brain networks.