Highlights
- •Bilateral prefrontal theta-tACS improves multitasking performance.
- •The improvements are coupled with changes across multiple oscillatory frequencies.
- •tACS effects on multitasking performance are not necessarily phase-dependent.
- •Changing the ISI of the stimulation protocol eliminated positive tACS effects.
- •Stimulation protocol is important for generating positive tACS effects.
Abstract
Background
We have previously demonstrated that transcranial alternating current stimulation
(tACS) can generate positive effects on multitasking performance and associated neurophysiological
measures when it is applied with anti-phase theta band stimulation across bilateral
prefrontal cortex (PFC) and a short (1-min) inter-session interval (ISI). However,
it is unclear how altering the phase of stimulation and the duration of the ISI might
impact positive tACS effects. Here, we investigated the role of tACS parameters in
engendering performance improvements by manipulating these two stimulation parameters
(i.e. phase and ISI) in two experiments.
Methods
Repetitive sessions of bilateral PFC theta-tACS were applied with in-phase stimulation +
1-min ISI (experiment 1) and anti-phase stimulation + 5-min ISI (experiment 2) while
participants were engaged in a multitasking challenge accompanied by electroencephalography
(EEG) data collection.
Results
Compared to the control group, in-phase stimulation + 1-min ISI showed an enhancement
of multitasking performance coupled with a modulation of posterior alpha (8–12 Hz)
and beta (13–30 Hz) activities. However, repetitive sessions of anti-phase tACS +
5-min ISI did not generate significant enhancement in multitasking performance, nor
changes in neural oscillatory activities compared to the control group.
Conclusion
The results revealed that the previous reported positive tACS effects on multitasking
performance are not affected by manipulating the phase of current polarity. Yet, changing
the ISI of the stimulation protocol eliminated the previous observed performance improvements.
Taken together, these results stress the importance of stimulation protocol for generating
positive tACS effects on cognitive function and neural oscillations.
Keywords
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Article info
Publication history
Published online: October 23, 2018
Accepted:
October 19,
2018
Received in revised form:
August 30,
2018
Received:
April 4,
2018
Identification
Copyright
© 2018 Elsevier Inc. All rights reserved.
