Institute of Cognitive Neuroscience, National Central University, Taoyuan, Taiwan; Cognitive Intelligence and Precision Healthcare Center, National Central University, Taoyuan, Taiwan; Brain Research Center, College of Health Sciences and Technology, National Central University, Taoyuan, Taiwan.
Graduate Institute of Mind, Brain and Consciousness, Taipei Medical University, Taipei, Taiwan; Brain and Consciousness Research Center, TMU-Shuang Ho Hospital, New Taipei City, Taiwan.
Neuroscience. 2021 Apr 15;460:69-87. doi: 10.1016/j.neuroscience.2021.02.013. Epub 2021 Feb 13.
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，这些活动通过各种振荡频率对信息进行编码。然而，之前的研究强调了时频功率变化，而忽略了节律幅度变化也可以在完全不同的维度上对特定频率的 VWM 信息进行编码的可能性。在这里，我们采用了最近开发的 Holo-Hilbert 谱分析来描述前额顶叶系统中 VWM 背后的这种非线性幅度调制（AM）。我们发现，在 VWM 维持和 VWM 检索期间，额中β和γ振荡的 AM 强度与人们的 VWM 表现相关。当通过经颅电刺激改变行为表现时，β频段的 AM 功率在 VWM 维持的后期发生变化，但γ频段没有，这与参与者的 VWM 变化有关。这种β AM 可能通过在θ周期内改变其幅度进行长距离传播来编码信息，因为我们的连接分析显示，在 VWM 维持期间，额中-右顶之间的θ-β双向耦合和在 VWM 维持和检索期间从右顶到左中枕叶的单向耦合，为 VWM 表现和个体差异提供了基础。
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