當(dāng)人的嗅覺(jué)被阻斷時(shí),，相應(yīng)的大腦活動(dòng)也會(huì)發(fā)生變化，不過(guò)這種變化會(huì)隨著嗅覺(jué)的恢復(fù)很快地逆轉(zhuǎn)復(fù)原,。先前的研究認(rèn)為嗅覺(jué)系統(tǒng)對(duì)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(xiàng)研究認(rèn)為嗅覺(jué)感知的穩(wěn)定性其實(shí)是因?yàn)榇竽X中存在快速補(bǔ)償變化,。
Keng Nei Wu等人通過(guò)完全堵住受試者的鼻孔來(lái)限制對(duì)其氣味的感知,，并讓受試者連續(xù)一個(gè)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(yàn)前后，受試者對(duì)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(dòng)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(dòng)便有所增加,，而初級(jí)嗅覺(jué)皮層的活動(dòng)則馬上減少。研究人員表示,，這種組合變化可能維持著嗅覺(jué)感知的穩(wěn)定性,。
在氣味感知受限一個(gè)星期后，大腦對(duì)氣味的反應(yīng)恢復(fù)到試驗(yàn)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(jué)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(jué)系統(tǒng),，對(duì)于無(wú)光的環(huán)境會(huì)產(chǎn)生持續(xù)時(shí)間較長(zhǎng)的反應(yīng),。科學(xué)家認(rèn)為之所以嗅覺(jué)系統(tǒng)會(huì)產(chǎn)生這種不同于其他感知系統(tǒng)的現(xiàn)象,，是因?yàn)樾嵊X(jué)的喪失一般是由病毒感染或過(guò)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.
