title: Neural signature of tDCS, tPCS and their combination: Comparing the effects on neural plasticity.
abstract: Transcranial pulsed current stimulation (tPCS) and transcranial direct current stimulation (tDCS) are two noninvasive neuromodulatory brain stimulation techniques whose effects on human brain and behavior have been studied individually. In the present study we aimed to quantify the effects of tDCS and tPCS, individually and in combination, on cortical activity, sensitivity and pain-related assessments in healthy individuals in order to understand their neurophysiological mechanisms and potential applications in clinical populations. A total of 48 healthy individuals participated in this randomized double blind sham controlled study. Participants were randomized to receive a single stimulation session of either: active or sham tPCS and active or sham tDCS. Quantitative electroencephalography (qEEG), sensitivity and pain assessments were used before and after each stimulation session. We observed that tPCS had a higher effect on power, as compared to tDCS, in several bandwidths on various cortical regions: the theta band in the parietal region (p=0.021), the alpha band in the temporal (p=0.009), parietal (p=0.0063), and occipital (p<0.0001) regions. We found that the combination of tPCS and tDCS significantly decreased power in the low beta bandwidth of the frontal (p=0.0006), central (p=0.0001), and occipital (p=0.0003) regions, when compared to sham stimulation. Additionally, tDCS significantly increased power in high beta over the temporal (p=0.0015) and parietal (p=0.0007) regions, as compared to sham. We found no effect on sensitivity or pain-related assessments. We concluded that tPCS and tDCS have different neurophysiological mechanisms, elicit distinct signatures, and that the combination of the two leads to no effect or a decrease on qEEG power. Further studies are required to examine the effects of these techniques on clinical populations in which EEG signatures have been found altered.
authors.affiliation: Spaulding-Labuschagne Neuromodulation Center, Spaulding Rehabilitation Hospital, Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, USA; Coma Science Group, GIGA-Research, University and University Hospital of Liege, Liege, Belgium.
authors.forename: Aurore
authors.initials: A
authors.lastname: Thibaut
authors.affiliation: Spaulding-Labuschagne Neuromodulation Center, Spaulding Rehabilitation Hospital, Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, USA; Department of Psychology and Milan Center for Neuroscience-NeuroMi, University of Milano-Bicocca, Milano, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Russo
authors.affiliation: Spaulding-Labuschagne Neuromodulation Center, Spaulding Rehabilitation Hospital, Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, USA.
authors.forename: Leon
authors.initials: L
authors.lastname: Morales-Quezada
authors.affiliation: Laboratory for Neuropsychiatry and Neuromodulation, Transcranial Magnetic Stimulation Clinical Service, Department of Psychiatry, Massachusetts General Hospital, Boston, USA.
authors.forename: Aura
authors.initials: A
authors.lastname: Hurtado-Puerto
authors.affiliation: Spaulding-Labuschagne Neuromodulation Center, Spaulding Rehabilitation Hospital, Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, USA; Post-graduate Program in Medical Sciences, School of Medicine, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil; Laboratory of Pain and Neuromodulation at UFRGS, Porto Alegre, Brazil.
authors.forename: Alícia
authors.initials: A
authors.lastname: Deitos
authors.affiliation: Division of Translational Research, Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Freedman
authors.affiliation: Spaulding-Labuschagne Neuromodulation Center, Spaulding Rehabilitation Hospital, Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, USA; Neuropsychophysiology Laboratory, CIPsi, School of Psychology (EPsi), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Sandra
authors.initials: S
authors.lastname: Carvalho
authors.affiliation: Spaulding-Labuschagne Neuromodulation Center, Spaulding Rehabilitation Hospital, Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, USA. Electronic address: felipe.fregni@mgh.harvard.edu.
authors.forename: Felipe
authors.initials: F
authors.lastname: Fregni
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D004311:Double-Blind Method; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009473:Neuronal Plasticity / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation / Q000379:methods; D055815:Young Adult
keywords: EEG; Non-invasive brain stimulation; Top-down/bottom-up connectivity; tDCS; tPCS