Transcutaneous spinal direct current stimulation modulates human corticospinal system excitability.
This study aimed to assess the effects of thoracic anodal and cathodal transcutaneous spinal direct current stimulation (tsDCS) on upper and lower limb corticospinal excitability. Although there have been studies assessing how thoracic tsDCS influences the spinal ascending tract and reflexes, none has assessed the effects of this technique over upper and lower limb corticomotor neuronal connections. In 14 healthy subjects we recorded motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) from abductor hallucis (AH) and hand abductor digiti minimi (ADM) muscles before (baseline) and at different time points (0 and 30 min) after anodal or cathodal tsDCS (2.5 mA, 20 min, T9-T11 level). In 8 of the 14 subjects we also tested the soleus H reflex and the F waves from AH and ADM before and after tsDCS. Both anodal and cathodal tsDCS left the upper limb MEPs and F wave unchanged. Conversely, while leaving lower limb H reflex unchanged, they oppositely affected lower limb MEPs: whereas anodal tsDCS increased resting motor threshold [(mean ± SE) 107.33 ± 3.3% increase immediately after tsDCS and 108.37 ± 3.2% increase 30 min after tsDCS compared with baseline] and had no effects on MEP area and latency, cathodal tsDCS increased MEP area (139.71 ± 12.9% increase immediately after tsDCS and 132.74 ± 22.0% increase 30 min after tsDCS compared with baseline) without affecting resting motor threshold and MEP latency. Our results show that tsDCS induces polarity-specific changes in corticospinal excitability that last for >30 min after tsDCS offset and selectively affect responses in lower limb muscles innervated by lumbar and sacral motor neurons.
Fondazione IRCCS "Ca' Granda" Ospedale Maggiore di Milano, Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Milan, Italy; Unità Operativa di Neurologia, Dipartimento di Neuroscienze, Università di Pisa, Pisa, Italy;
Tommaso
T
Bocci
Fondazione IRCCS "Ca' Granda" Ospedale Maggiore di Milano, Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Milan, Italy; Dipartimento di Ingegneria e Architettura, Università degli Studi di Trieste, Trieste, Italy; and.
Sara
S
Marceglia
Fondazione IRCCS "Ca' Granda" Ospedale Maggiore di Milano, Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Milan, Italy;
Maurizio
M
Vergari
Fondazione IRCCS "Ca' Granda" Ospedale Maggiore di Milano, Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Milan, Italy;
Valeria
V
Cognetto
Fondazione IRCCS "Ca' Granda" Ospedale Maggiore di Milano, Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Milan, Italy;
Filippo
F
Cogiamanian
Unità Operativa di Neurologia, Dipartimento di Neuroscienze, Università di Pisa, Pisa, Italy; Istituto di Neuroscienze, Consiglio Nazionale delle Ricerche, Pisa, Italy.
Ferdinando
F
Sartucci
Fondazione IRCCS "Ca' Granda" Ospedale Maggiore di Milano, Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Milan, Italy; alberto.priori@unimi.it.
Alberto
A
Priori
D000328:Adult; D001921:Brain / Q000502:physiology*; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D006181:H-Reflex / Q000502:physiology; D006801:Humans; D035002:Lower Extremity / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D011712:Pyramidal Tracts / Q000502:physiology*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D004561:Transcutaneous Electric Nerve Stimulation / Q000379:methods; D034941:Upper Extremity / Q000502:physiology
corticospinal system; direct current stimulation; motor potentials; spinal cord; spinal cord stimulation; transcranial direct current stimulation; transcranial magnetic stimulation; transcutaneous spinal direct current stimulation