Neuronal tissue polarization induced by repetitive transcranial magnetic stimulation?
In a blinded cross-over design, 10 healthy controls received 900 monophasic and biphasic repetitive transcranial magnetic stimuli over the primary motor cortex. Stimulation frequency was 1 Hz, and stimulation intensity 90% of the individual resting motor threshold. Suprathreshold stimuli applied at 0.1 Hz before and after repetitive stimulation controlled for changes in corticospinal excitability. We found a lasting corticospinal inhibition that was significantly more pronounced after monophasic than after biphasic repetitive transcranial magnetic stimulation (motor evoked potential amplitude reduced by 35 +/- 20% vs 12 +/- 37%, mean+/- s.d.). We propose that the current flow in the coil plays a significant role in optimising after effects, and asymmetric current flow may be particularly efficient in building up tissue polarization.
Sommer
Martin
M
Department of Clinical Neurophysiology, University of Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany.
Lang
Nicolas
N
Tergau
Frithjof
F
Paulus
Walter
W
D000328:Adult; D004599:Electric Stimulation Therapy / Q000379:methods*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009044:Motor Cortex / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000627:therapeutic use