Visual 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-middle-occipital during late VWM maintenance and retrieval—underpins VWM performance and individual differences.

视觉工作记忆（VWM）依赖于持续的神经活动，该活动通过各种振荡频率对信息进行编码。然而，先前的研究强调时频功率变化，而忽略了有节奏的幅度变化的可能性。变化还可以在完全不同的维度上编码特定于频率的VWM信息。在这里，我们采用了最新开发的Holo-Hilbert光谱分析来表征额前系统中VWM的这种非线性幅度调制（AM）。我们发现，在后期VWM维护和VWM检索期间，中额β和伽马振荡的AM强度与人们的VWM性能相关。当经颅电刺激改变行为表现时，在晚期VWM维持期间，β值（而不是伽马值）期间的AM功率变化会跟踪参与者的VWM变化。这个beta AM可能会通过改变theta周期内的幅度进行信息编码，以进行远程传播，