Processing of Feature Selectivity in Cortical Networks with Specific Connectivity

Although non-specific at the onset of eye opening, networks in rodent visual cortex attain a non-random structure after eye opening, with a specific bias for connections between neurons of similar preferred orientations. As orientation selectivity is already present at eye opening, it remains unclear how this specificity in network wiring contributes to feature selectivity. Using large-scale inhibition-dominated spiking networks as a model, we show that feature-specific connectivity leads to a linear amplification of feedforward tuning, consistent with recent electrophysiological single-neuron recordings in rodent neocortex. Our results show that optimal amplification is achieved at an intermediate regime of specific connectivity. In this configuration a moderate increase of pairwise correlations is observed, consistent with recent experimental findings. Furthermore, we observed that feature-specific connectivity leads to the emergence of orientation-selective reverberating activity, and entails pattern completion in network responses. Our theoretical analysis provides a mechanistic understanding of subnetworks’ responses to visual stimuli, and casts light on the regime of operation of sensory cortices in the presence of specific connectivity.尽管啮齿类视觉皮层（rodent visual cortex）的神经网络在睁眼初期尚无特异性，但在睁眼后会形成非随机结构，且对具有相似偏好朝向的神经元之间的连接存在特定偏向。由于朝向选择性（orientation selectivity）在睁眼时便已存在，目前学界尚未明确这种网络连接特异性如何促成特征选择性。本研究以大规模抑制占优的脉冲神经网络为模型，证实特征特异性连接可实现前馈调谐（feedforward tuning）的线性放大，这一结果与近期啮齿类新皮层（rodent neocortex）中的电生理单细胞记录结果相符。我们的研究表明，最优放大效应出现在特征特异性连接的中间运作区间。在此配置下，可观察到成对相关性（pairwise correlations）的适度增强，这与近期实验发现一致。此外，特征特异性连接还会催生具有朝向选择性的回响活动（reverberating activity），并实现网络响应的模式补全（pattern completion）。本研究的理论分析为阐释子网络（subnetworks）对视觉刺激的响应提供了机制层面的理解，并为阐明存在特异性连接时感觉皮层（sensory cortices）的运作区间指明了方向。