title: Time Course of Corticospinal Excitability and Autonomic Function Interplay during and Following Monopolar tDCS.
abstract: While polarity-specific after-effects of monopolar transcranial direct current stimulation (tDCS) on corticospinal excitability are well-documented, modulation of vital parameters due to current spread through the brainstem is still a matter of debate, raising potential concerns about its use through the general public, as well as for neurorehabilitation purposes. We monitored online and after-effects of monopolar tDCS (primary motor cortex) in 10 healthy subjects by adopting a neuronavigated transcranial magnetic stimulation (TMS)/tDCS combined protocol. Motor evoked potentials (MEPs) together with vital parameters [e.g., blood pressure, heart-rate variability (HRV), and sympathovagal balance] were recorded and monitored before, during, and after anodal, cathodal, or sham tDCS. Ten MEPs, every 2.5-min time windows, were recorded from the right first dorsal interosseous (FDI), while 5-min epochs were used to record vital parameters. The protocol included 15 min of pre-tDCS and of online tDCS (anodal, cathodal, or sham). After-effects were recorded for 30 min. We showed a polarity-independent stabilization of cortical excitability level, a polarity-specific after-effect for cathodal and anodal stimulation, and an absence of persistent excitability changes during online stimulation. No significant effects on vital parameters emerged both during and after tDCS, while a linear increase in systolic/diastolic blood pressure and HRV was observed during each tDCS condition, as a possible unspecific response to experimental demands. Taken together, current findings provide new insights on the safety of monopolar tDCS, promoting its application both in research and clinical settings.
authors.affiliation: Unit of Neurology and Neurophysiology, Department of Medicine, Surgery and Neuroscience, University of Siena , Siena , Italy ; Brain Investigation and Neuromodulation Lab, University of Siena , Siena , Italy.
authors.forename: Emiliano
authors.initials: E
authors.lastname: Santarnecchi
authors.affiliation: Unit of Neurology and Neurophysiology, Department of Medicine, Surgery and Neuroscience, University of Siena , Siena , Italy ; Brain Investigation and Neuromodulation Lab, University of Siena , Siena , Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Feurra
authors.affiliation: Brain Investigation and Neuromodulation Lab, University of Siena , Siena , Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Barneschi
authors.affiliation: U.O.C. Stroke Unit, Department of Medicine, Surgery and Neuroscience, Le Scotte Policlinic , Siena , Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Acampa
authors.affiliation: Brain Investigation and Neuromodulation Lab, University of Siena , Siena , Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bianco
authors.affiliation: Unit of Neurology and Neurophysiology, Department of Medicine, Surgery and Neuroscience, University of Siena , Siena , Italy ; Brain Investigation and Neuromodulation Lab, University of Siena , Siena , Italy.
authors.forename: David
authors.initials: D
authors.lastname: Cioncoloni
authors.affiliation: Unit of Neurology and Neurophysiology, Department of Medicine, Surgery and Neuroscience, University of Siena , Siena , Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Rossi
authors.affiliation: Unit of Neurology and Neurophysiology, Department of Medicine, Surgery and Neuroscience, University of Siena , Siena , Italy ; Brain Investigation and Neuromodulation Lab, University of Siena , Siena , Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Rossi
keywords: neuromodulation; safety; transcranial direct current stimulation; transcranial magnetic stimulation; vital parameters
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