Brain State-dependent Brain Stimulation with Real-time Electroencephalography-Triggered Transcranial Magnetic Stimulation

The effect of a stimulus to the brain depends not only on the parameters of the stimulus but also on the dynamics of brain activity at the timeof the stimulation. The combination of electroencephalography (EEG) and transcranial magnetic stimulation (TMS) in a real-time brain state-dependent stimulation system allows the study of relations of dynamics of brain activity, cortical excitability, and plasticity induction. Here,we demonstrate a newly developed method to synchronize the timing of brain stimulation with the phase of ongoing EEG oscillations usinga real-time data analysis system. This real-time EEG-triggered TMS of the human motor cortex, when TMS is synchronized with the surfaceEEG negative peak of the sensorimotor μ-alpha (8-14 Hz) rhythm, has shown differential corticospinal excitability and plasticity effects. Theutilization of this method suggests that real-time information about the instantaneous brain state can be used for efficacious plasticity induction.Additionally, this approach enables personalized EEG-synchronized brain stimulation which may lead to the development of more effectivetherapeutic brain stimulation protocols.