title: 40Hz-Transcranial alternating current stimulation (tACS) selectively modulates speech perception.
abstract: The present study investigated the functional relevance of gamma oscillations for the processing of rapidly changing acoustic features in speech signals. For this purpose we analyzed repetition-induced perceptual learning effects in 18 healthy adult participants. The participants received either 6Hz or 40Hz tACS over the bilateral auditory cortex, while repeatedly performing a phoneme categorization task. In result, we found that 40Hz tACS led to a specific alteration in repetition-induced perceptual learning. While participants in the non-stimulated control group as well as those in the experimental group receiving 6Hz tACS considerably improved their perceptual performance, the application of 40Hz tACS selectively attenuated the repetition-induced improvement in phoneme categorization abilities. Our data provide causal evidence for a functional relevance of gamma oscillations during the perceptual learning of acoustic speech features. Moreover, we demonstrate that even less than twenty minutes of alternating current stimulation below the individual perceptual threshold is sufficient to affect speech perception. This finding is relevant in that this novel approach might have implications with respect to impaired speech processing in dyslexics and older adults.
authors.affiliation: Research Unit for Neuroplasticity and Learning of the Healthy Aging Brain, University of Zurich, Switzerland; Department of Neurology, Otto-von-Guericke University Magdeburg, Germany. Electronic address: katharina.rufener@med.ovgu.de.
authors.forename: Katharina S
authors.initials: KS
authors.lastname: Rufener
authors.affiliation: Department of Neurology, Otto-von-Guericke University Magdeburg, Germany.
authors.forename: Tino
authors.initials: T
authors.lastname: Zaehle
authors.affiliation: International Normal Aging and Plasticity Imaging Center, Zurich, Switzerland.
authors.forename: Mathias S
authors.initials: MS
authors.lastname: Oechslin
authors.affiliation: University Research Priority Program "Dynamics of Healthy Aging", University of Zurich, Switzerland; Research Unit for Neuroplasticity and Learning of the Healthy Aging Brain, University of Zurich, Switzerland; International Normal Aging and Plasticity Imaging Center, Zurich, Switzerland; Cognitive Psychology Unit (CPU), University of Klagenfurt, Klagenfurt am Wörthersee, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Meyer
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D000513:Alpha Rhythm / Q000502:physiology*; D001303:Auditory Cortex / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D013067:Speech Perception / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D055815:Young Adult
keywords: Perceptual learning; Phoneme processing; Transcranial alternating current stimulation