Abstract

Synchronized oscillatory gamma-band activity (30-100Hz) has been suggested to constitute a key mechanism to dynamically orchestrate sensory information integration across multiple spatio-temporal scales. We here tested whether interhemispheric functional connectivity and ensuing auditory perception can selectively be modulated by high-density transcranial alternating current stimulation (HD-tACS). For this purpose, we applied multi-site HD-tACS at 40Hz bilaterally with a phase lag of 180° and recorded a 64-channel EEG to study the oscillatory phase dynamics at the source-space level during a dichotic listening (DL) task in twenty-six healthy participants. In this study, we revealed an oscillatory phase signature at 40Hz which reflects different temporal profiles of the phase asymmetries during left and right ear percept. Here we report that 180°-tACS did not affect the right ear advantage during DL at group level. However, a follow-up analysis revealed that the intrinsic phase asymmetries during sham-tACS determined the directionality of the behavioral modulations: While a shift to left ear percept was associated with augmented interhemispheric asymmetry (closer to 180°), a shift to right ear processing was elicited in subjects with lower asymmetry (closer to 0°). Crucially, the modulation of the interhemispheric network dynamics depended on the deviation of the tACS-induced phase-lag from the intrinsic phase asymmetry. Our characterization of the oscillatory network trends is giving rise to the importance of phase-specific gamma-band coupling during ambiguous auditory perception, and emphasizes the necessity to address the inter-individual variability of phase asymmetries in future studies by tailored stimulation protocols.

Highlights

  • The right ear advantage was present during both sham- (LISham: M = 23.714±18.557) and verum-transcranial alternating current stimulation (tACS) (LIVerum: M = 24.756±21.535) as participants perceived significantly more syllables presented to the right ear than to the left ear, which was confirmed by two-sided ttests for both tACS-sessions (sham: t(25) = 6.480; p < .001, d = 2.43; verum: t(25) = 5.809; p < .001 d = 2.22)

  • We argue that the selective modulation of conscious auditory perception might depend on the deviation of the exogenous from the endogenous phase lag: The interhemispheric network was prone to inhibition when the intrinsic lag differed strongly from the transcranially-induced 180 ̊-lag, whereas a shift to left ear percept was facilitated when the deviation of the tACS-induced lag from the intrinsic lag was low

  • This study provides novel insights into how the intrinsic phase relationship can be exploited as a significant network parameter for the implementation of optimized stimulation protocols

Read more

Summary

Objectives

Our goal was to keep results comparable with our supplementary reliability analysis, as classical test theory demands an equal number of observations throughout all subjects for the assessment of reliability scores [38]

Methods
Results
Discussion
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call