當(dāng)人的嗅覺被阻斷時，相應(yīng)的大腦活動也會發(fā)生變化,，不過這種變化會隨著嗅覺的恢復(fù)很快地逆轉(zhuǎn)復(fù)原,。先前的研究認(rèn)為嗅覺系統(tǒng)對氣味喪失之后的感知變化具有一定的抵抗性，但是本周《自然—神經(jīng)科學(xué)》雜志上的一項研究認(rèn)為嗅覺感知的穩(wěn)定性其實是因為大腦中存在快速補(bǔ)償變化,。
Keng Nei Wu等人通過完全堵住受試者的鼻孔來限制對其氣味的感知,，并讓受試者連續(xù)一個星期呆在醫(yī)院的低氣味監(jiān)護(hù)室中。結(jié)果發(fā)現(xiàn)在試驗前后,，受試者對氣味的感受很大程度上并未發(fā)生改變,。但是，與氣味相關(guān)的大腦活動卻有所變化,。在氣味感知受限后,，受試者大腦眶額皮層的活動便有所增加,，而初級嗅覺皮層的活動則馬上減少。研究人員表示,，這種組合變化可能維持著嗅覺感知的穩(wěn)定性,。
在氣味感知受限一個星期后，大腦對氣味的反應(yīng)恢復(fù)到試驗前的水平,，這表示這種以氣味受限的方式引發(fā)的變化已經(jīng)快速逆轉(zhuǎn)了,。嗅覺系統(tǒng)的這種快速逆轉(zhuǎn)與其他感知系統(tǒng)有很大不同，比如視覺系統(tǒng),，對于無光的環(huán)境會產(chǎn)生持續(xù)時間較長的反應(yīng),。科學(xué)家認(rèn)為之所以嗅覺系統(tǒng)會產(chǎn)生這種不同于其他感知系統(tǒng)的現(xiàn)象,，是因為嗅覺的喪失一般是由病毒感染或過敏癥引起的,。（生物谷Bioon.com）
doi:10.1038/nn.3186
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Olfactory input is critical for sustaining odor quality codes in human orbitofrontal cortex
Keng Nei Wu, Bruce K Tan, James D Howard, David B Conley & Jay A Gottfried
Ongoing sensory input is critical for shaping internal representations of the external world. Conversely, a lack of sensory input can profoundly perturb the formation of these representations. The olfactory system is particularly vulnerable to sensory deprivation, owing to the widespread prevalence of allergic, viral and chronic rhinosinusitis, but how the brain encodes and maintains odor information under such circumstances remains poorly understood. Here we combined functional magnetic resonance imaging (fMRI) with multivariate (pattern-based) analyses and psychophysical approaches to show that a 7-d period of olfactory deprivation induces reversible changes in odor-evoked fMRI activity in piriform cortex and orbitofrontal cortex (OFC). Notably, multivoxel ensemble codes of odor quality in OFC became decorrelated after deprivation, and the magnitude of these changes predicted subsequent olfactory perceptual plasticity. Our findings suggest that transient changes in these key olfactory brain regions are instrumental in sustaining odor perception integrity in the wake of disrupted sensory input.
