Padmanabhan Krishnan, Osakada Fumitaka, Tarabrina Anna, Kizer Erin, Callaway Edward M, Gage Fred H, Sejnowski Terrence J
Crick-Jacobs Center for Theoretical and Computational Biology, Salk Institute for Biological Studies, La Jolla, CA, United States.
Computational Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, United States.
Front Neuroanat. 2019 Jan 7;12:115. doi: 10.3389/fnana.2018.00115. eCollection 2018.
Neuronal activity in sensory regions can be modulated by attention, behavioral state, motor output, learning, and memory. This is often done through direct feedback or centrifugal projections originating from higher processing areas. Though, functionally important, the identity and organization of these feedback connections remain poorly characterized. Using a retrograde monosynaptic g-deleted rabies virus and whole-brain reconstructions, we identified the organization of feedback projecting neurons to the main olfactory bulb of the mouse. In addition to previously described projections from regions such as the Anterior Olfactory Nucleus (AON) and the piriform cortex, we characterized direct projections from pyramidal cells in the ventral CA1 region of hippocampus and the entorhinal cortex to the granule cell layer (GCL) of the main olfactory bulb (MOB). These data suggest that areas involved in stress, anxiety, learning and memory are all tethered to olfactory coding, two synapses away from where chemical compounds are first detected. Consequently, we hypothesize that understanding olfactory perception, even at the earliest stages, may require studying memory and behavior in addition to studying the physiochemical features of odors.
感觉区域的神经元活动可受到注意力、行为状态、运动输出、学习和记忆的调节。这通常是通过源自更高处理区域的直接反馈或离心投射来实现的。虽然这些反馈连接在功能上很重要，但其身份和组织特征仍不清楚。我们使用逆行单突触g缺失狂犬病毒和全脑重建技术，确定了向小鼠主嗅球投射反馈的神经元的组织方式。除了先前描述的来自前嗅核（AON）和梨状皮质等区域的投射外，我们还确定了海马腹侧CA1区和内嗅皮质的锥体细胞向主嗅球（MOB）颗粒细胞层（GCL）的直接投射。这些数据表明，参与应激、焦虑、学习和记忆的区域都与嗅觉编码相关，距离首次检测到化合物的位置有两个突触之遥。因此，我们推测，即使在最早阶段，理解嗅觉感知可能除了研究气味的物理化学特征外，还需要研究记忆和行为。
