title: Both the cutaneous sensation and phosphene perception are modulated in a frequency-specific manner during transcranial alternating current stimulation.
abstract: OBJECTIVE
  Transcranial alternating current stimulation (tACS) is a non-invasive stimulation technique for shaping neuroplastic processes and possibly entraining ongoing neural oscillations in humans. Despite the growing number of studies using tACS, we know little about the procedural sensations caused by stimulation. In order to fill this gap, we explored the cutaneous sensation and phosphene perception during tACS.
  
  
  METHODS
  Twenty healthy participants took part in a randomized, single-blinded, sham-controlled study, where volunteers received short duration stimulation at 1.0 mA intensity between 2 to 250 Hz using the standard left motor cortex-contralateral supraorbital montage. We recorded the perception onset latency and the strength of the sensations assessed by visual rating scale as dependent variables.
  
  
  RESULTS
  We found that tACS evoked both cutaneous sensation and phosphene perception in a frequency-dependent manner. Our results show that the most perceptible procedural sensations were induced in the beta and gamma frequency range, especially at 20 Hz, whereas minimal procedural sensations were indicated in the ripple range (140 and 250 Hz).
  
  
  CONCLUSIONS
  We believe that our results provide a relevant insight into the procedural sensations caused by oscillatory currents, and will offer a basis for developing more sophisticated stimulation protocols and study designs for future investigations.
authors.affiliation: Department of Clinical Neurophysiology, Georg-August University of Göttingen, Göttingen, Germany. zsoltturi@gmail.com
authors.forename: Zs
authors.initials: Z
authors.lastname: Turi
authors.forename: G G
authors.initials: GG
authors.lastname: Ambrus
authors.forename: K
authors.initials: K
authors.lastname: Janacsek
authors.forename: K
authors.initials: K
authors.lastname: Emmert
authors.forename: L
authors.initials: L
authors.lastname: Hahn
authors.forename: W
authors.initials: W
authors.lastname: Paulus
authors.forename: A
authors.initials: A
authors.lastname: Antal
mesh_terms: D000328:Adult; D004558:Electric Stimulation / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D010465:Perception / Q000502:physiology*; D010719:Phosphenes / Q000502:physiology*; D012677:Sensation / Q000502:physiology*; D012867:Skin; D012879:Skin Physiological Phenomena; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D014793:Visual Cortex / Q000502:physiology; D055815:Young Adult