title: 4-Hz Transcranial Alternating Current Stimulation Phase Modulates Hearing.
abstract: BACKGROUND
  Non-invasive brain stimulation with transcranial alternating currents (tACS) has been shown to entrain slow cortical oscillations and thereby influence various aspects of visual perception. Much less is known about its potential effects on auditory perception.
  
  
  OBJECTIVE
  In the present study, we apply a novel variant that enables near-equivalent stimulation of both auditory cortices to investigate the causal role of the phase of 4-Hz cortical oscillations for auditory perception.
  
  
  METHODS
  We measured detection performance for near-threshold auditory stimuli (4-Hz click trains) that were presented at various moments during ongoing tACS (two synchronous 4-Hz alternating currents applied transcranially to the two cerebral hemispheres).
  
  
  RESULTS
  We found that changes in the relative timing of acoustic and electric stimulation cause corresponding perceptual changes that oscillate predominantly at the 4-Hz frequency of the electric stimulation, which is consistent with previous results based on 10-Hz tACS.
  
  
  CONCLUSIONS
  TACS at various frequencies can affect auditory perception. Together with converging previous results based on acoustic stimulation (rather than tACS), this finding implies that fundamental aspects of auditory cognition are mediated by the temporal coherence of sound-induced cortical activity with ongoing cortical oscillations at multiple time scales.
authors.affiliation: Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Oxfordlaan 55, 6229 EV Maastricht, The Netherlands. Electronic address: L.Riecke@MaastrichtUniversity.nl.
authors.forename: Lars
authors.initials: L
authors.lastname: Riecke
authors.affiliation: Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Oxfordlaan 55, 6229 EV Maastricht, The Netherlands.
authors.forename: Elia
authors.initials: E
authors.lastname: Formisano
authors.affiliation: Experimental Psychology Lab, Department of Psychology, Cluster for Excellence "Hearing4all", European Medical School, University of Oldenburg, Ammerländer Heerstrasse 114-118, 26129 Oldenburg, Germany; Research Center Neurosensory Science, University of Oldenburg, Carl-von-Ossietzky-Strasse 9-11, 26111 Oldenburg, Germany.
authors.forename: Christoph S
authors.initials: CS
authors.lastname: Herrmann
authors.affiliation: Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Oxfordlaan 55, 6229 EV Maastricht, The Netherlands.
authors.forename: Alexander T
authors.initials: AT
authors.lastname: Sack
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001303:Auditory Cortex / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D058256:Brain Waves / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult
keywords: Auditory cortex; Entrainment; Hearing; Oscillation; tACS