大脑如何在瞬息万变的环境中准确感知气味？中科院武汉物理与数学研究所最近的研究结果发现，嗅觉系统的第一中枢——嗅球——在脑不同的运行状态下对气味的响应总强度大致相同，说明人或动物对气味的分别并不是在嗅球完成，可能是在更高级的嗅觉中枢实现。
这一研究成果，3月22日发表于美国科学院院刊，并入选为封面文章之一。耶鲁大学FahmeedHyder教授专门撰文评论该成果。除中科院武汉物数所外，武汉光电国家实验室和湖北第二师范学院也参与了该研究。
据论文作者之一李安安博士介绍，该结果从另一方面来看，嗅球能把不同脑状态下获取的嗅觉信息真实可靠地送到更高级中枢。
相对于科学界对视觉与听觉的深入研究，嗅觉研究相对较少。嗅觉对于动物早期生存，寻找食物和配偶，认知猎物和天敌，都非常重要。嗅觉也明显地影响人类的生理心理及社会行为。中科院武汉物数所嗅觉神经生物学课题组重点研究对象是嗅球——在嗅觉的信息编码、处理和传送过程中占有重要地位的脑区。
课题组通过对麻醉深度的操控，使动物大脑处于不同的运行状态，并记录两种状态下嗅球对气味刺激的反应。结果发现，嗅球中的神经总活动和神经元放电频率分布，在气味刺激后与各自基线相比均发生明显改变，但气味刺激后两种状态之间相比，并无明显差别。进一步的实验证实，大脑在不同状态下，一种尚待研究的神经机制可确保对气味准确编码，将外界气味信息可靠地传递到嗅球，形成相应的嗅觉感知。
此成果对于人们进一步了解感觉系统，如何在不同条件下完成高保真的信息输入，有积极作用。（生物谷Bioon.com）
生物谷推荐原文出处：
PNAS doi: 10.1073/pnas.1013814108
Brain-state–independent neural representation of peripheral stimulation in rat olfactory bulb
Anan Lia,b, Ling Gonga, and Fuqiang Xua,c,1
Abstract
It is critical for normal brains to perceive the external world precisely and accurately under ever-changing operational conditions, yet the mechanisms underlying this fundamental brain function in the sensory systems are poorly understood. To address this issue in the olfactory system, we investigated the responses of olfactory bulbs to odor stimulations under different brain states manipulated by anesthesia levels. Our results revealed that in two brain states, where the spontaneous baseline activities differed about twofold based on the local field potential (LFP) signals, the levels of neural activities reached after the same odor stimulation had no significant difference. This phenomenon was independent of anesthetics (pentobarbital or chloral hydrate), stimulating odorants (ethyl propionate, ethyl butyrate, ethyl valerate, amyl acetate, n-heptanal, or 2-heptanone), odor concentrations, and recording sites (the mitral or granular cell layers) for LFPs in three frequency bands (12–32 Hz, 33–64 Hz, and 65–90 Hz) and for multiunit activities. Furthermore, the activity patterns of the same stimulation under these two brain states were highly similar at both LFP and multiunit levels. These converging results argue the existence of mechanisms in the olfactory bulbs that ensure the delivery of peripheral olfactory information to higher olfactory centers with high fidelity under different brain states.
