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Updated: Mar 21, 2026
Transcranial Direct Current Stimulation and Simultaneous Functional Magnetic Resonance Imaging
Published on: April 27, 2014
Transcranial Alternating Current Stimulation (tACS) differentially modulates speech perception in young and older
Katharina S Rufener1, Mathias S Oechslin2, Tino Zaehle3
1Department of Neurology, Otto-von-Guericke University, Magdeburg, Germany; Research Unit for Neuroplasticity and Learning of the Healthy Aging Brain, University of Zurich, Switzerland.
Background:
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.
Objective:
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.
Methods:
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.
Results:
While 40 Hz tACS diminished task accuracy in young adults, older adults benefitted from this stimulation resulting in a more precise phonetic categorization.
Conclusion:
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.
