The trial-to-trial response variability in sensory cortices and the extent to which this variability can be coordinated among cortical units have strong implications for cortical signal processing. Yet, little is known about the relative contributions and dynamics of defined sources to the cortical response variability and their correlations across cortical units. To fill this knowledge gap, here we obtained and analyzed multisite local field potential (LFP) recordings from visual cortex of turtles in response to repeated naturalistic movie clips and decomposed cortical across-trial LFP response variability into three defined sources, namely, input, network, and local fluctuations. We found that input fluctuations dominate cortical response variability immediately following stimulus onset, whereas network fluctuations dominate the response variability in the steady state during continued visual stimulation. Concurrently, we found that the network fluctuations dominate the correlations of the variability during the ongoing and steady-state epochs, but not immediately following stimulus onset. Furthermore, simulations of various model networks indicated that (i) synaptic time constants, leading to oscillatory activity, and (ii) synaptic clustering and synaptic depression, leading to spatially constrained pockets of coherent activity, are both essential features of cortical circuits to mediate the observed relative contributions and dynamics of input, network, and local fluctuations to the cortical LFP response variability and their correlations across recording sites. In conclusion, these results show how a mélange of multiscale thalamocortical circuit features mediate a complex stimulus-modulated cortical activity that, when naively related to the visual stimulus alone, appears disguised as high and coordinated across-trial response variability.

中文翻译：

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视觉皮层反应变异的动力学和来源及其协调

感觉皮层的试验间反应变异性以及这种变异性在皮层单位之间的协调程度对皮层信号处理具有重要意义。然而，关于已定义来源对皮层反应变异性及其跨皮层单元的相关性的相对贡献和动态知之甚少。为了填补这一知识空白，我们从海龟的视觉皮层获得并分析了多点局部场电位 (LFP) 记录，以响应重复的自然主义电影剪辑，并将皮质跨试验 LFP 响应变异性分解为三个定义的源，即输入、网络, 和局部波动。我们发现输入波动在刺激开始后立即主导皮层反应变异性，而网络波动在持续的视觉刺激期间主导稳态的响应变化。同时，我们发现网络波动在持续和稳态时期主导了变异性的相关性，但不是在刺激开始后立即发生。此外，各种模型网络的模拟表明（i）突触时间常数，导致振荡活动，和（ii）突触聚集和突触抑制，导致空间受限的连贯活动口袋，都是皮层电路介导观察到输入、网络和局部波动对皮质 LFP 响应变异性及其在记录站点之间的相关性的相对贡献和动态。综上所述，