Yang Weiguo, Sun Qian-Quan
Department of Zoology and Physiology, University of Wyoming, Laramie, WY Graduate Neuroscience Program, University of Wyoming, Laramie, WY.
Department of Zoology and Physiology, University of Wyoming, Laramie, WY
Physiol Rep. 2015 Sep;3(9). doi: 10.14814/phy2.12550.
How sensory information is processed within olfactory cortices is unclear. Here, we examined long-range circuit wiring between different olfactory cortical regions of acute mouse brain slices using a channelrhodopsin-2 (ChR2)-based neuronal targeting approach. Our results provide detailed information regarding the synaptic properties of the reciprocal long-range monosynaptic glutamatergic projections (LRMGP) between and within anterior piriform cortex (aPC), posterior piriform cortex (pPC), and lateral entorhinal cortex (LEC), thereby creating a long-range inter- and intracortical circuit diagrams at the level of synapses and single cortical neurons. Our results reveal the following information regarding hierarchical intra- and intercortical organizations: (i) there is massive bottom-up (i.e., rostral-caudal) excitation within the LRMGP accompanied with strong feedforward (FF) inhibition; (ii) there are convergent FF connections onto LEC from both aPC and pPC; (iii) feedback (FB) intercortical connections are weak with a significant fraction of presumptive silent synapses; and (iv) intra and intercortical long-range connections lack layer specificity and their innervation of interneurons are stronger than neighboring pyramidal neurons. The elucidation of the distinct hierarchical organization of long-range olfactory cortical circuits paves the way for further understanding of higher order cortical processing within the olfactory system.
嗅觉信息在嗅觉皮层内是如何被处理的尚不清楚。在这里，我们使用基于通道视紫红质-2（ChR2）的神经元靶向方法，研究了急性小鼠脑片不同嗅觉皮层区域之间的长程回路连接。我们的结果提供了关于梨状前皮质（aPC）、梨状后皮质（pPC）和外侧内嗅皮质（LEC）之间以及内部相互的长程单突触谷氨酸能投射（LRMGP）的突触特性的详细信息，从而在突触和单个皮层神经元水平上创建了一个长程皮质间和皮质内回路图。我们的结果揭示了以下关于皮质内和皮质间层次组织的信息：（i）LRMGP内存在大量自下而上（即从前到后）的兴奋，并伴有强烈的前馈（FF）抑制；（ii）aPC和pPC都有汇聚到LEC的FF连接；（iii）反馈（FB）皮质间连接较弱，有相当一部分推测为沉默突触；（iv）皮质内和皮质间的长程连接缺乏层特异性，它们对中间神经元的支配强于相邻的锥体神经元。对长程嗅觉皮质回路独特层次组织的阐明为进一步理解嗅觉系统内的高级皮质处理铺平了道路。
