Sensory Circuits and Neurotechnology Laboratory, Francis Crick Institute, London NW1 1AT, United Kingdom
Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, United Kingdom.
J Neurosci. 2022 May 25;42(21):4278-4296. doi: 10.1523/JNEUROSCI.1422-21.2022. Epub 2022 Apr 19.
Odors are transported by turbulent air currents, creating complex temporal fluctuations in odor concentration that provide a potentially informative stimulus dimension. We have shown that mice are able to discriminate odor stimuli based on their temporal structure, indicating that information contained in the temporal structure of odor plumes can be extracted by the mouse olfactory system. Here, using extracellular and intracellular electrophysiological recordings, we show that mitral cells (MCs) and tufted cells (TCs) of the male C57BL/6 mouse olfactory bulb can encode the dominant temporal frequencies present in odor stimuli up to at least 20 Hz. A substantial population of cell-odor pairs showed significant coupling of their subthreshold membrane potential with the odor stimulus at both 2 Hz (29/70) and the suprasniff frequency 20 Hz (24/70). Furthermore, mitral/tufted cells (M/TCs) show differential coupling of their membrane potential to odor concentration fluctuations with tufted cells coupling more strongly for the 20 Hz stimulation. Frequency coupling was always observed to be invariant to odor identity, and M/TCs that coupled well to a mixture also coupled to at least one of the components of the mixture. Interestingly, pharmacological blocking of the inhibitory circuitry strongly modulated frequency coupling of cell-odor pairs at both 2 Hz (10/15) and 20 Hz (9/15). These results provide insight into how both cellular and circuit properties contribute to the encoding of temporal odor features in the mouse olfactory bulb. Odors in the natural environment have a strong temporal structure that can be extracted and used by mice in their behavior. Here, using extracellular and intracellular electrophysiological techniques, we show that the projection neurons in the olfactory bulb can encode and couple to the dominant frequency present in an odor stimulus. Furthermore, frequency coupling was observed to be differential between mitral and tufted cells and was odor invariant but strongly modulated by local inhibitory circuits. In summary, this study provides insight into how both cellular and circuit properties modulate encoding of odor temporal features in the mouse olfactory bulb.
气味通过湍流空气传播，在气味浓度中产生复杂的时间波动，为潜在的信息刺激维度提供了基础。我们已经表明，老鼠能够根据气味的时间结构来区分气味刺激，这表明老鼠的嗅觉系统可以从气味羽流的时间结构中提取信息。在这里，我们使用细胞外和细胞内电生理记录，表明雄性 C57BL/6 小鼠嗅球的僧帽细胞（MCs）和锥形细胞（TCs）可以对刺激气味中存在的主要时间频率进行编码，其频率高达至少 20Hz。相当一部分细胞-气味对在 2Hz（29/70）和嗅阈以上的 20Hz（24/70）时，其亚阈膜电位与气味刺激有显著的耦合。此外，与气味浓度波动的僧帽/锥形细胞（M/TCs）的膜电位有明显的耦合，而锥形细胞的耦合更强，在 20Hz 刺激时。频率耦合总是与气味身份无关，对混合物耦合良好的 M/TCs 也与混合物的至少一个成分耦合。有趣的是，抑制性电路的药理学阻断强烈调节了 2Hz（10/15）和 20Hz（9/15）时的细胞-气味对的频率耦合。这些结果提供了一些线索，说明细胞和电路特性如何共同作用，从而对小鼠嗅球中气味的时间特征进行编码。在自然环境中，气味具有很强的时间结构，可以被老鼠在其行为中提取和利用。在这里，我们使用细胞外和细胞内电生理技术，表明嗅球中的投射神经元可以对气味刺激中的主导频率进行编码并进行耦合。此外，我们观察到，在僧帽细胞和锥形细胞之间存在频率耦合的差异，这种差异与气味无关，但被局部抑制性电路强烈调制。总之，这项研究为我们提供了一些线索，说明细胞和电路特性如何共同作用，从而对小鼠嗅球中气味的时间特征进行编码。
