Visual attention is a selective process of visual information and improves perceptual performance by modulating activities of neurons in the visual system. It has been reported that attention increased firing rates of neurons, reduced their response variability and improved reliability of coding relevant stimuli. Recent neurophysiological studies demonstrated that attention also enhanced the synaptic efficacy between neurons mediated through NMDA and AMPA receptors. Majority of computational models of attention usually are based on firing rates, which cannot explain attentional modulations observed at the synaptic level. To understand mechanisms of attentional modulations at the synaptic level, we proposed a neural network consisting of three layers, corresponding to three different brain regions. Each layer has excitatory and inhibitory neurons. Each neuron was modeled by the Hodgkin–Huxley model. The connections between neurons were through excitatory AMPA and NMDA receptors, as well as inhibitory GABA_A receptors. Since the binding process of neurotransmitters with receptors is stochastic in the synapse, it is hypothesized that attention could reduce the variation of the stochastic binding process and increase the fraction of bound receptors in the model. We investigated how attention modulated neurons’ responses at the synaptic level on the basis of this hypothesis. Simulated results demonstrated that attention increased firing rates of neurons and reduced their response variability. The attention-induced effects were stronger in higher regions compared to those in lower regions, and stronger for inhibitory neurons than for excitatory neurons. In addition, AMPA receptor antagonist (CNQX) impaired attention-induced modulations on neurons’ responses, while NMDA receptor antagonist (APV) did not. These results suggest that attention may modulate neuronal activity at the synaptic level.

中文翻译：

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具有多层的皮质模型，用于研究突触水平神经元的视觉注意调节。

视觉注意力是视觉信息的选择性过程，通过调节视觉系统中神经元的活动来提高感知性能。据报道，注意力增加了神经元的放电率，减少了它们的反应变异性并提高了编码相关刺激的可靠性。最近的神经生理学研究表明，注意力还增强了通过 NMDA 和 AMPA 受体介导的神经元之间的突触功效。大多数注意力计算模型通常基于放电率，这无法解释在突触水平上观察到的注意力调节。为了理解突触层面的注意力调节机制，我们提出了一个由三层组成的神经网络，对应于三个不同的大脑区域。每层都有兴奋性和抑制性神经元。每个神经元均由霍奇金-赫胥黎模型建模。神经元之间的连接是通过兴奋性 AMPA 和 NMDA 受体以及抑制性 GABA _A受体实现的。由于神经递质与受体的结合过程在突触中是随机的，因此假设注意力可以减少随机结合过程的变化并增加模型中结合受体的比例。基于这一假设，我们研究了注意力如何在突触水平上调节神经元的反应。模拟结果表明，注意力增加了神经元的放电率并降低了它们的反应变异性。与较低区域相比，较高区域的注意力诱导效应更强，并且抑制性神经元的注意力诱导效应比兴奋性神经元更强。此外，AMPA 受体拮抗剂 (CNQX) 会损害注意力诱导的神经元反应调节，而 NMDA 受体拮抗剂 (APV) 则不会。这些结果表明注意力可能会调节突触水平的神经元活动。