Nesse William H, Bahmani Zahra, Clark Kelsey, Noudoost Behrad
Department of Mathematics, University of Utah, Salt Lake City, UT, United States.
Department of Biomedical Engineering, Tarbiat Modares University, Tehran, Iran.
Front Comput Neurosci. 2021 May 20;15:632730. doi: 10.3389/fncom.2021.632730. eCollection 2021.
Extrastriate visual neurons show no firing rate change during a working memory (WM) task in the absence of sensory input, but both αβ oscillations and spike phase locking are enhanced, as is the gain of sensory responses. This lack of change in firing rate is at odds with many models of WM, or attentional modulation of sensory networks. In this article we devised a computational model in which this constellation of results can be accounted for via selective activation of inhibitory subnetworks by a top-down working memory signal. We confirmed the model prediction of selective inhibitory activation by segmenting cells in the experimental neural data into putative excitatory and inhibitory cells. We further found that this inhibitory activation plays a dual role in influencing excitatory cells: it both modulates the inhibitory tone of the network, which underlies the enhanced sensory gain, and also produces strong spike-phase entrainment to emergent network oscillations. Using a phase oscillator model we were able to show that inhibitory tone is principally modulated through inhibitory network gain saturation, while the phase-dependent efficacy of inhibitory currents drives the phase locking modulation. The dual contributions of the inhibitory subnetwork to oscillatory and non-oscillatory modulations of neural activity provides two distinct ways for WM to recruit sensory areas, and has relevance to theories of cortical communication.
在没有感觉输入的工作记忆（WM）任务期间，纹外视觉神经元的放电率没有变化，但αβ振荡和尖峰相位锁定都增强了，感觉反应的增益也是如此。这种放电率缺乏变化与许多工作记忆模型或感觉网络的注意力调制不一致。在本文中，我们设计了一个计算模型，通过自上而下的工作记忆信号对抑制性子网络的选择性激活，可以解释这一系列结果。我们通过将实验神经数据中的细胞分为假定的兴奋性和抑制性细胞，证实了模型对选择性抑制激活的预测。我们进一步发现，这种抑制性激活在影响兴奋性细胞方面发挥双重作用：它既调节网络的抑制性基调，这是增强感觉增益的基础，又对出现的网络振荡产生强烈的尖峰相位夹带。使用相位振荡器模型，我们能够表明抑制性基调主要通过抑制性网络增益饱和来调节，而抑制性电流的相位依赖性功效驱动相位锁定调制。抑制性子网络对神经活动的振荡和非振荡调制的双重贡献为工作记忆招募感觉区域提供了两种不同的方式，并且与皮层通信理论相关。
