Depicting Transcranial Magnetic Stimulation from a Neuronal Perspective

Transcranial magnetic stimulation (TMS) is a widely used non-invasive tool to study and modulate human brain functions. However, our knowledge of TMS neurophysiology is largely limited due to various difficulties in studying neural activities in vivo in real-time under the strong electromagnetic interference generated by TMS. In this work, the author first reviews the state-of-the-art knowledge in the neurophysiology of TMS and highlights the need to conduct further studies at the level of individual neurons and their neural networks. The second chapter is dedicated to the technical development of a research platform that allows faithful concurrent TMS and EEP recording in laboratory rodents. Building on this methodology, the third chapter focuses on characterizing the dynamics of neuronal activities in M1 evoked by a monophasic single-pulse TMS (mspTMS) that triggers unilateral MEPs in the forearm. Bringing the investigation further, the fourth chapter explores the mechanism of TMS-evoked intermediate excitation, a period of synaptic-mediated excitatory neuronal activities in M1 triggered by TMS, in the cortico-basal ganglia-thalamo-cortical (CBGTC) and the cortico-cerebello-thalamo-cortical (CCTC) loop. Finally, the fifth chapter summarizes the results from this work, discusses their limitations and implications, and proposes future research