Asymmetric synaptic depression in cortical networks
Asymmetric synaptic depression in cortical networks
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DOI：
10.1093/cercor/bhm119
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发表时间：
2008-04-01
期刊：
影响因子：
3.7
通讯作者：
Dragoi, Valentin
中科院分区：
文献类型：
--
作者：
Chelaru, Mircea I.;Dragoi, Valentin
突触抑制对于控制皮质网络兴奋和抑制之间的平衡至关重要。多项研究表明，皮质内突触的抑制是不对称的，即抑制性突触的抑制程度小于兴奋性突触的抑制程度。这种不对称性是否对皮质功能有任何影响尚不清楚。在这里，我们表明，皮质内突触的差异抑制提供了一种机制，通过该机制，皮质回路的增益和敏感性随时间变化，以改善刺激编码。我们通过对初级视觉皮层（V1）中适应前馈输入的方向选择性神经元之间的反复相互作用进行建模，研究了不对称突触抑制的功能后果。我们通过分析证明，尽管兴奋性突触比抑制性突触抑制更多，但兴奋性反应的减少程度小于抑制性反应，从而增加了总体反应增益。这些变化在视觉皮层回路中产生选择性增益控制方面发挥着积极作用。具体来说，不对称突触抑制通过放大 V1 神经元对不频繁刺激的反应和敏感性并减弱对频繁刺激的反应和敏感性来调节网络选择性，正如实验中所观察到的那样。
Synaptic depression is essential for controlling the balance between excitation and inhibition in cortical networks. Several studies have shown that the depression of intracortical synapses is asymmetric, that is, inhibitory synapses depress less than excitatory ones. Whether this asymmetry has any impact on cortical function is unknown. Here we show that the differential depression of intracortical synapses provides a mechanism through which the gain and sensitivity of cortical circuits shifts over time to improve stimulus coding. We examined the functional consequences of asymmetric synaptic depression by modeling recurrent interactions between orientation-selective neurons in primary visual cortex (V1) that adapt to feedforward inputs. We demonstrate analytically that despite the fact that excitatory synapses depress more than inhibitory synapses, excitatory responses are reduced less than inhibitory ones to increase the overall response gain. These changes play an active role in generating selective gain control in visual cortical circuits. Specifically, asymmetric synaptic depression regulates network selectivity by amplifying responses and sensitivity of V1 neurons to infrequent stimuli and attenuating responses and sensitivity to frequent stimuli, as is indeed observed experimentally.