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Low-frequency alternating current stimulation rhythmically suppresses gamma-band oscillations and impairs perceptual performance.

Donders Institute, Radboud University Nijmegen, Nijmegen, the Netherlands. CUBRIC, School of Psychology, Cardiff University, Cardiff, United Kingdom; Donders Institute, Radboud University Nijmegen, Nijmegen, the Netherlands. Department of Experimental Psychology, University of Oxford, United Kingdom; Donders Institute, Radboud University Nijmegen, Nijmegen, the Netherlands. School of Psychology, University of Birmingham, Birmingham, United Kingdom; Donders Institute, Radboud University Nijmegen, Nijmegen, the Netherlands. Department of Neurology and Stroke, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany; Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen, Germany; Donders Institute, Radboud University Nijmegen, Nijmegen, the Netherlands. Electronic address: til.bergmann@uni-tuebingen.de.

NeuroImage. 2019;:440-449
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Abstract

Low frequency oscillations such as alpha (8-12 Hz) are hypothesized to rhythmically gate sensory processing, reflected by 40-100 Hz gamma band activity, via the mechanism of pulsed inhibition. We applied transcranial alternating current stimulation (TACS) at individual alpha frequency (IAF) and flanking frequencies (IAF-4 Hz, IAF+4 Hz) to the occipital cortex of healthy human volunteers during concurrent magnetoencephalography (MEG), while participants performed a visual detection task inducing strong gamma-band responses. Occipital (but not retinal) TACS phasically suppressed stimulus-induced gamma oscillations in the visual cortex and impaired target detection, with stronger phase-to-amplitude coupling predicting behavioral impairments. Retinal control TACS ruled out retino-thalamo-cortical entrainment resulting from (subthreshold) retinal stimulation. All TACS frequencies tested were effective, suggesting that visual gamma-band responses can be modulated by a range of low frequency oscillations. We propose that TACS-induced membrane potential modulations mimic the rhythmic change in cortical excitability by which spontaneous low frequency oscillations may eventually exert their impact when gating sensory processing via pulsed inhibition.