title: Duration Dependent Effects of Transcranial Pulsed Current Stimulation (tPCS) Indexed by Electroencephalography.
abstract: OBJECTIVE
  To explore the duration of tPCS after effects given different durations of stimulation on power and interhemispheric coherence of the EEG frequency bands. Our hypothesis was that longer tPCS duration would induce a differential effect on the EEG analysis and a longer duration of after effects on the EEG frequency bands.
  
  
  METHODS
  We conducted a double blind, sham controlled study in which forty healthy subjects were randomized to receive a single session of either 10, 20, 30 min of active (2 mA, random frequency between 6 and 10 Hz, ear clip montage) or sham tPCS. EEG was recorded before and after the intervention to assess tPCS induced after effects.
  
  
  RESULTS
  We found that 10 and 20 min of active tPCS induced a significant increase in alpha (p = 0.004) and theta (p = 0.006) coherence in the frontal region as compared with the sham stimulation. No significant changes were found with 30 min of stimulation (p < 0.05). The Kaplan Meier analysis showed that 10 and 20 min of tPCS induced after effects that lasted 50 min.
  
  
  CONCLUSIONS
  These results evidence the nonlinear relationship between the stimulation duration and the tPCS after effects, suggesting the presence of homeostatic mechanisms.
authors.affiliation: Spaulding Neuromodulation Center, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Vasquez
authors.affiliation: Spaulding Neuromodulation Center, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Malavera
authors.affiliation: Spaulding Neuromodulation Center, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Deniz
authors.initials: D
authors.lastname: Doruk
authors.affiliation: Spaulding Neuromodulation Center, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA.|Department of Physical Medicine and Rehabilitation, School of Health Sciences, De Montfort University, Leicester, UK.|Division of General Medicine and Primary Care, Beth Israel Deaconess Medical Center, Brookline, MA, USA.
authors.forename: Leon
authors.initials: L
authors.lastname: Morales-Quezada
authors.affiliation: Spaulding Neuromodulation Center, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA.|Neuropsychophysiology Laboratory, CIPsi, School of Psychology, University of Minho, Campus de Gualtar, Braga, Portugal.
authors.forename: Sandra
authors.initials: S
authors.lastname: Carvalho
authors.affiliation: Spaulding Neuromodulation Center, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA.|Neuropsychophysiology Laboratory, CIPsi, School of Psychology, University of Minho, Campus de Gualtar, Braga, Portugal.
authors.forename: Jorge
authors.initials: J
authors.lastname: Leite
authors.affiliation: Spaulding Neuromodulation Center, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA. felipe.fregni@ppcr.hms.harvard.edu.
authors.forename: Felipe
authors.initials: F
authors.lastname: Fregni
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D058256:Brain Waves / Q000502:physiology*; D004311:Double-Blind Method; D004569:Electroencephalography; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D064368:Healthy Volunteers; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D013997:Time Factors; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D055815:Young Adult
keywords: EEG; homeostatic plasticity; interhemispheric coherence; power spectrum; transcranial pulsed current stimulation