Frontoparietal Beta Amplitude Modulation and its Interareal Cross-frequency Coupling in Visual Working Memory

working memory (VWM) relies on sustained neural activities that code information via various oscillatory frequencies. Previous studies, however, have emphasized time?frequency power changes, while overlooking the possibility that rhythmic amplitude variations can also code frequency-specific VWM information in a completely different dimension. Here, we employed the recently-developed Holo-Hilbert spectral analysis to characterize such nonlinear amplitude modulation(s) (AM) underlying VWM in the frontoparietal systems. We found that the strength of AM in mid-frontal beta and gamma oscillations during late VWM maintenance and VWM retrieval correlated with people?s VWM performance. When behavioral performance was altered with transcranial electric stimulation, AM power changes during late VWM maintenance in beta, but not gamma, tracked participants? VWM variations. This beta AM likely codes information by varying its amplitude in theta period for long-range propagation, as our connectivity analysis revealed that interareal theta-beta couplings?bidirectional between mid-frontal and right-parietal during VWM maintenance and unidirectional from right-parietal to left-middleoccipital during late VWM maintenance and retrieval?underpins VWM performance and individual differences. ? 2021 IBRO. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study found that AM strength in mid-frontal beta and gamma oscillations during late VWM maintenance and retrieval correlated with individuals' VWM performance. When altering behavioral performance with transcranial electric stimulation, changes in beta AM power during late VWM maintenance tracked participants' VWM variations, highlighting the potential role of beta AM in coding VWM information.