感覺系統的基本功能是準確地把瞬息萬變的環境信息提供給大腦，而大腦的一個基本功能是在不斷變化的內環境下，準確地感知外部世界。這樣的正常功能，對于日常生活、生存以及腦功能如在適當的情形下做出正確的判斷、計劃以及zui終決定等至關重要。然而，感覺系統如何在不同的生理狀態下完成高保真的輸入，我們的了解卻十分有限。

中科院武漢物理與數學研究所徐富強研究員和李安安博士等人以嗅覺系統的*中樞嗅球作為研究對象，通過對麻醉深度的操控，使動物大腦處于不同的運行狀態（高基線和低基線兩種狀態），利用電生理記錄的方法研究動物在這兩種情況下嗅球如何編碼同一氣味刺激的信息。研究表明，動物在處于這兩種運行狀態下，嗅球中的神經總活動和神經元放電頻率分布，在氣味刺激后與各自基線相比均發生明顯改變，但氣味刺激后兩種狀態之間相比，并無明顯差別。這種對同一刺激獨立于大腦狀態的神經表達現象并不受所使用的麻醉劑類型、氣味結構和濃度、嗅球的不同功能層、同一功能層內不同的位點以及電信號類型（不同頻段的局部場電位和多單位放電）的影響。因此，嗅球對同一氣味刺激的編碼是通過相對穩定的神經元組合，以反應強度而不是相對反應強度來實現，同時提示嗅球中存在目前還不清楚的神經機制來確保在不同大腦狀態下對氣味準確編碼，從而將外界氣味信息可靠地傳遞到更的嗅覺中樞，形成相應的嗅覺感知。

研究結果Brain-state–independent neural representation ofperipheral stimulation in rat olfactory bulb發表在美國《國家*院刊》（PNAS）上.

該研究得到國家自然科學基金委杰出青年基金、國家創新研究群體和中科院“百人計劃”項目的支持。（轉生物谷Bioon.com）

原文出處：

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 accuray 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.