Enhancing the effects of theta-burst magnetic stimulation over the motor cortex: the role of muscular activity and stimulation intensity

Introduction: Metaplasticity refers to the activity-dependent modification of the ability of synapses to undergo subsequent potentiation or depression, and is thought to maintain homeostasis of cortical excitability. Theta-burst stimulation is a novel repetitive magnetic stimulation protocol used to model changes of synaptic efficacy in human motor cortex. It consists of 50Hz-bursts of 3 magnetic stimuli at 80% of the active motor threshold (AMT) repeated at 5Hz. Two modalities of TBS have been established: intermittent TBS (iTBS) and continuous TBS (cTBS). ITBS generates a facilitatory effect reflected by an in…