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Theta Phase-Dependent Modulation of Perception by Concurrent tACS and Periodic Visual Stimulation

Somer, Elif; Allen, John; Brooks, Joseph L.; Buttrill, Vaughan; Javadi, Amir-Homayoun


Elif Somer

John Allen

Vaughan Buttrill

Amir-Homayoun Javadi


Sensory perception can be modulated by the phase of neural oscillations, especially in the theta and alpha ranges. Oscillatory activity in the visual cortex can be entrained by transcranial alternating current stimulation (tACS) as well as periodic visual stimulation (i.e., flicker). Combined tACS and visual flicker stimulation modulates BOLD responses and concurrent 4-Hz auditory click trains, and tACS modulates auditory perception in a phase-dependent way. In this study, we investigated if phase synchrony between concurrent tACS and periodic visual stimulation (i.e., flicker) can modulate performance on a visual matching task. Participants completed a visual matching task on a flickering visual stimulus while receiving either in-phase (0°) or asynchronous (180°, 90°, or 270°) tACS at alpha or theta frequency. Stimulation was applied over either occipital cortex or dorsolateral pFC. Visual performance was significantly better during theta frequency tACS over the visual cortex when it was in-phase (0°) with visual stimulus flicker, compared with antiphase (180°). This effect did not appear with alpha frequency flicker or with dorsolateral pFC stimulation. Furthermore, a control sham group showed no effect. There were no significant performance differences among the asynchronous (180°, 90°, and 270°) phase conditions. Extending previous studies on visual and auditory perception, our results support a crucial role of oscillatory phase in sensory perception and demonstrate a behaviorally relevant combination of visual flicker and tACS. The spatial and frequency specificity of our results have implications for research on the functional organization of perception.


Somer, E., Allen, J., Brooks, J. L., Buttrill, V., & Javadi, A. (2020). Theta Phase-Dependent Modulation of Perception by Concurrent tACS and Periodic Visual Stimulation. Journal of Cognitive Neuroscience, 32(6), 1142-1152.

Journal Article Type Article
Acceptance Date Jan 8, 2020
Publication Date Apr 30, 2020
Journal Journal of Cognitive Neuroscience
Print ISSN 0898-929X
Publisher Massachusetts Institute of Technology Press
Peer Reviewed Peer Reviewed
Volume 32
Issue 6
Pages 1142-1152
Keywords Theta, phase-dependent, tACS, periodic visual stimulation.
Publisher URL