TMS bursts can modulate local and networks oscillations during lower-limb movement

Introduction: Lower-limb motor functions involve processing information via both motor and cognitive control networks. Measuring oscillations is a key element in communication within and between cortical networks during high order motor functions. Increased midfrontal theta oscillations are related to improved lower-limb motor performances in patients with movement disorders. Non-invasive neuromodulation approaches have not been explored extensively to understand the oscillatory mechanism of lower-limb motor functions. This study aims to examine the effects of repetitive transcranial magnetic stimulation (rTMS) on local and network EEG oscillations in healthy elderly subjects. Methods: Eleven healthy elder subjects (67-73 years) were recruited via advertisements, and underwent both active and sham stimulation procedures in a random, counterbalanced design. TMS bursts (θ-TMS; 4 pulses/sec) were applied over the midfrontal lead (vertex) before a GO-Cue pedaling task, and signals were analyzed using time-frequency methods. Results: TMS bursts increase the theta activity in the local (p=0.02), as well as the associated network during the lower-limb pedaling task (p = 0.02). Furthermore, after task-related TMS burst sessions, increased resting-state alpha activity was observed in the midfrontal region (p= 0.01). Conclusion: Our study suggests the ability of midfrontal TMS bursts to directly modulate local and network oscillations in a frequency manner during lower-limb motor task. TMS burst-induced modulation may provide insights into the functional roles of oscillatory activity during lower-limb movement in normal and disease conditions.