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.