November 25, 2021 | 5 pm | Zoom
Real-time EEG-TMS for brain state-dependent stimulation in humans.
The electrophysiological states of the brain change rapidly over time. Different states show differential responsivity to a given input. Real-time analysis of brain states can be done with electroencephalography (EEG). We demonstrated that different phases of the sensorimotor μ-oscillation reflect differential excitability states of the corticospinal system by measuring motor evoked potential (MEP) amplitudes when transcranial magnetic stimulation (TMS) pulses were applied to either the peak or trough of the ongoing μ-rhythm. TMS at the trough resulted in larger MEPs than TMS at the peak. We also demonstrated that repetitive burst-TMS resulted in long-term potentiation (LTP)-like increase in MEP amplitudes, but only when the high-excitability state (trough) was targeted, not when the low-excitability state (peak) was targeted with the otherwise identical TMS protocol. First clinical applications of this brain state-dependent TMS will also be presented. In summary, we provide evidence that the instantaneous brain state is decisive on the magnitude and direction of repetitive TMS effects. Further development of brain state-dependent and closed-loop stimulation approaches will very likely soon lead to a paradigm shift in the field of therapeutic brain stimulation.