Short-term plasticity regulates the strength of central synapses as a function of previous activity. In the neocortex, direct synaptic interactions between areas play a central role in cognitive function, but the activity-dependent regulation of these long-range corticocortical connections and their impact on a postsynaptic target neuron is unclear. Here, we use an optogenetic strategy to study the connections between mouse primary somatosensory and motor cortex. We found that short-term facilitation was strong in both corticocortical synapses, resulting in far more sustained responses than local intracortical and thalamocortical connections. A major difference between pathways was that the synaptic strength and magnitude of facilitation were distinct for individual excitatory cells located across all cortical layers and specific subtypes of GABAergic neurons. Facilitation was dependent on the presynaptic calcium sensor synaptotagmin-7 and altered by several optogenetic approaches. Current-clamp recordings revealed that during repetitive activation, the short-term dynamics of corticocortical synapses enhanced the excitability of layer 2/3 pyramidal neurons, increasing the probability of spiking with activity. Furthermore, the properties of the connections linking primary with secondary somatosensory cortex resemble those between somatosensory–motor areas. These short-term changes in transmission properties suggest long-range corticocortical synapses are specialized for conveying information over relatively extended periods.

中文翻译：

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选择性光刺激揭示长程皮质皮质突触的短期促进作用

短期可塑性调节中央突触的强度，作为先前活动的函数。在新皮质中，区域之间的直接突触相互作用在认知功能中起着核心作用，但这些远程皮质皮质连接的活动依赖性调节及其对突触后目标神经元的影响尚不清楚。在这里，我们使用光遗传学策略来研究小鼠初级体感和运动皮层之间的联系。我们发现皮质皮质突触的短期促进作用很强，导致比局部皮质内和丘脑皮质连接更持久的反应。通路之间的一个主要区别是突触强度和易化程度对于位于所​​有皮层层和特定 GABA 能神经元亚型的单个兴奋性细胞是不同的。促进依赖于突触前钙传感器 synaptotagmin-7 并通过几种光遗传学方法改变​​。电流钳记录显示，在重复激活期间，皮质皮质突触的短期动态增强了锥体 2/3 层神经元的兴奋性，增加了活动峰值的可能性。此外，连接初级体感皮层和次级体感皮层的连接特性类似于体感运动区之间的连接特性。