title: Transcranial Alternating Current Stimulation (tACS) differentially modulates speech perception in young and older adults.
abstract: Normal aging is accompanied by a functional decline in processing temporal features of spoken language, such as voice onset time (VOT). On an electrophysiological level, this finding is paralleled by altered patterns of gamma oscillations.
  
  
  
  Using 40 Hz transcranial alternating current stimulation (tACS) over the bilateral auditory cortex, this study aims to compare the effect of tACS to modulate VOT-processing in samples of healthy young and older adults.
  
  
  
  Twenty-five healthy young (age 20-35 years) and 20 older adults (age 60-75 years) participated in this study. Presented with an auditory phoneme categorization task participants received 40 Hz and 6 Hz tACS on two consecutive sessions.
  
  
  
  While 40 Hz tACS diminished task accuracy in young adults, older adults benefitted from this stimulation resulting in a more precise phonetic categorization.
  
  
  
  The results of the study are discussed with respect to the non-linear relationship between gamma oscillations in the vicinity of the auditory cortex and VOT-processing. The present findings are promising in the context of an intervention for subjects with impaired ability to process temporal acoustic features in the speech signal.
authors.affiliation: Department of Neurology, Otto-von-Guericke University, Magdeburg, Germany; Research Unit for Neuroplasticity and Learning of the Healthy Aging Brain, University of Zurich, Switzerland. Electronic address: katharina.rufener@med.ovgu.de.
authors.forename: Katharina S
authors.initials: KS
authors.lastname: Rufener
authors.affiliation: International Normal Aging and Plasticity Imaging Center, Zurich, Switzerland.
authors.forename: Mathias S
authors.initials: MS
authors.lastname: Oechslin
authors.affiliation: Department of Neurology, Otto-von-Guericke University, Magdeburg, Germany.
authors.forename: Tino
authors.initials: T
authors.lastname: Zaehle
authors.affiliation: Research Unit for Neuroplasticity and Learning of the Healthy Aging Brain, University of Zurich, Switzerland; International Normal Aging and Plasticity Imaging Center, Zurich, Switzerland; University Research Priority Program "Dynamics of Healthy Aging", University of Zurich, Switzerland; Cognitive Psychology Unit (CPU), University of Klagenfurt, Klagenfurt am Wörthersee, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Meyer
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001303:Auditory Cortex / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013067:Speech Perception / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D055815:Young Adult
keywords: Aging; Auditory processing; Transcranial alternating current stimulation (tACS); Voice onset time (VOT)