Wu Ruiqi, Liu Yue, Wang Li, Li Bo, Xu Fuqiang
State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Key Laboratory of Magnetic Resonance in Biological System, Wuhan Institute of Physics and Mathematics, Center of Excellence for Brain Science and Intelligent Technology, the Chinese Academy of Sciences, Wuhan 430071, China, and
Wuhan National Laboratory for Optoelectronics, Wuhan 430074, China.
J Neurosci. 2017 Nov 1;37(44):10700-10711. doi: 10.1523/JNEUROSCI.2210-17.2017. Epub 2017 Oct 2.
Olfactory sensory neurons (OSNs) can sense both odorants and airflows. In the olfactory bulb (OB), the coding of odor information has been well studied, but the coding of mechanical stimulation is rarely investigated. Unlike odor-sensing functions of OSNs, the airflow-sensing functions of OSNs are also largely unknown. Here, the activity patterns elicited by mechanical airflow in male rat OBs were mapped using fMRI and correlated with local field potential recordings. In an attempt to reveal possible functions of airflow sensing, the relationship between airflow patterns and physiological parameters was also examined. We found the following: (1) the activity pattern in the OB evoked by airflow in the nasal cavity was more broadly distributed than patterns evoked by odors; (2) the pattern intensity increases with total airflow, while the pattern topography with total airflow remains almost unchanged; and (3) the heart rate, spontaneous respiratory rate, and electroencephalograph power in the β band decreased with regular mechanical airflow in the nasal cavity. The mapping results provide evidence that the signals elicited by mechanical airflow in OSNs are transmitted to the OB, and that the OB has the potential to code and process mechanical information. Our functional data indicate that airflow rhythm in the olfactory system can regulate the physiological and brain states, providing an explanation for the effects of breath control in meditation, yoga, and Taoism practices. Presentation of odor information in the olfactory bulb has been well studied, but studies about breathing features are rare. Here, using blood oxygen level-dependent functional MRI for the first time in such an investigation, we explored the global activity patterns in the rat olfactory bulb elicited by airflow in the nasal cavity. We found that the activity pattern elicited by airflow is broadly distributed, with increasing pattern intensity and similar topography under increasing total airflow. Further, heart rate, spontaneous respiratory rate in the lung, and electroencephalograph power in the β band decreased with regular airflow in the nasal cavity. Our study provides further understanding of the airflow map in the olfactory bulb o, and evidence for the possible mechanosensitivity functions of olfactory sensory neurons.
嗅觉感觉神经元（OSNs）既能感知气味分子，也能感知气流。在嗅球（OB）中，气味信息的编码已得到充分研究，但机械刺激的编码却很少被研究。与OSNs的气味感知功能不同，其气流感知功能也大多未知。在此，利用功能磁共振成像（fMRI）绘制了雄性大鼠嗅球中机械气流引发的活动模式，并将其与局部场电位记录相关联。为了揭示气流感知的可能功能，还研究了气流模式与生理参数之间的关系。我们发现以下几点：（1）鼻腔气流在嗅球中引发的活动模式比气味引发的模式分布更广；（2）模式强度随总气流增加而增加，而模式拓扑结构随总气流几乎保持不变；（3）鼻腔中规则的机械气流会使心率、自发呼吸频率和β波段脑电图功率降低。映射结果提供了证据，表明OSNs中机械气流引发的信号会传递到嗅球，且嗅球有对机械信息进行编码和处理的潜力。我们的功能数据表明，嗅觉系统中的气流节律可以调节生理和大脑状态，这为冥想、瑜伽和道教修行中呼吸控制的效果提供了解释。嗅球中气味信息的呈现已得到充分研究，但关于呼吸特征的研究却很少。在此，我们首次在这样的研究中使用血氧水平依赖性功能磁共振成像，探索了鼻腔气流在大鼠嗅球中引发的全局活动模式。我们发现气流引发的活动模式分布广泛，随着总气流增加，模式强度增加且拓扑结构相似。此外，鼻腔中规则的气流会使心率、肺部自发呼吸频率和β波段脑电图功率降低。我们的研究进一步加深了对嗅球中气流图谱的理解，并为嗅觉感觉神经元可能的机械敏感性功能提供了证据。
