Laboratory for Sensory Circuit Formation, RIKEN Center for Developmental Biology, Kobe 650-0047, Japan.
Animal Resource Development Unit and Genetic Engineering Team, RIKEN Center for Life Science Technologies, Kobe 650-0047, Japan.
Neuron. 2017 Dec 6;96(5):1139-1152.e7. doi: 10.1016/j.neuron.2017.11.008.
Mitral and tufted (M/T) cells in the olfactory bulb produce rich temporal patterns of activity in response to different odors. However, it remains unknown how these temporal patterns are generated and how they are utilized in olfaction. Here we show that temporal patterning effectively discriminates between the two sensory modalities detected by olfactory sensory neurons (OSNs): odor and airflow-driven mechanical signals. Sniff-induced mechanosensation generates glomerulus-specific oscillatory activity in M/T cells, whose phase was invariant across airflow speed. In contrast, odor stimulation caused phase shifts (phase coding). We also found that odor-evoked phase shifts are concentration invariant and stable across multiple sniff cycles, contrary to the labile nature of rate coding. The loss of oscillatory mechanosensation impaired the precision and stability of phase coding, demonstrating its role in olfaction. We propose that phase, not rate, coding is a robust encoding strategy of odor identity and is ensured by airflow-induced mechanosensation in OSNs.
嗅球中的二尖瓣和簇状（M/T）细胞对不同气味会产生丰富的时间活动模式。然而，目前尚不清楚这些时间模式是如何产生的，以及它们在嗅觉中是如何被利用的。在这里，我们表明时间模式可以有效地区分嗅感觉神经元（OSN）检测到的两种感觉模式：气味和气流驱动的机械信号。嗅诱导的机械感觉会在 M/T 细胞中产生特定于神经球的振荡活动，其相位在气流速度上是不变的。相比之下，气味刺激会引起相位移动（相位编码）。我们还发现，气味诱发的相位移动与浓度无关，并且在多个嗅探周期中保持稳定，这与比率编码的不稳定性相反。振荡机械感觉的丧失损害了相位编码的精度和稳定性，证明了其在嗅觉中的作用。我们提出，相位而不是速率编码是气味身份的稳健编码策略，并且由 OSN 中的气流诱导的机械感觉来保证。
