Center for Neural Circuits and Behavior and Department of Neurosciences, University of California, San Diego, La Jolla, United States.
Elife. 2022 Feb 7;11:e75065. doi: 10.7554/eLife.75065.
Olfactory information is encoded in lateral entorhinal cortex (LEC) by two classes of layer 2 (L2) principal neurons: fan and pyramidal cells. However, the functional properties of L2 cells and how they contribute to odor coding are unclear. Here, we show in awake mice that L2 cells respond to odors early during single sniffs and that LEC is essential for rapid discrimination of both odor identity and intensity. Population analyses of L2 ensembles reveal that rate coding distinguishes odor identity, but firing rates are only weakly concentration dependent and changes in spike timing can represent odor intensity. L2 principal cells differ in afferent olfactory input and connectivity with inhibitory circuits and the relative timing of pyramidal and fan cell spikes provides a temporal code for odor intensity. Downstream, intensity is encoded purely by spike timing in hippocampal CA1. Together, these results reveal the unique processing of odor information by LEC subcircuits and highlight the importance of temporal coding in higher olfactory areas.
嗅觉信息由两种类型的 2 层(L2)主神经元在外侧缰核(LEC)中编码:扇区细胞和锥体细胞。然而,L2 细胞的功能特性以及它们如何有助于气味编码尚不清楚。在这里,我们在清醒的小鼠中表明,L2 细胞在单次嗅探的早期对气味做出反应,并且 LEC 对于快速区分气味身份和强度是必不可少的。L2 细胞群体分析表明,速率编码区分气味身份,但放电率仅与浓度弱相关,而尖峰时间的变化可以表示气味强度。主细胞在传入的嗅觉输入和与抑制回路的连接以及尖峰和扇区细胞尖峰的相对时间上存在差异,为气味强度提供了时间编码。在下游,强度仅由海马 CA1 中的尖峰时间编码。总的来说,这些结果揭示了 LEC 子电路对气味信息的独特处理,并强调了时间编码在较高嗅觉区域的重要性。