生物谷报道：你或许听说过，一些人的鼻子有感知危险的特异功能。美国西北大学（Northwestern University, 生物谷注）最新研究表明，人类的鼻子确实能嗅出危险。人的大脑嗅觉区能建立糟糕经历与当时气味间的联系。因此当麻烦或危险再次临近时，鼻子能立刻闻出这种气味，并发出避开危险的“警报”。
西北大学研究人员通过一项实验，证明鼻子与危险有不可思议的联系。当实验志愿者闻特定气味时，研究人员以轻微电击刺激他们，使他们的大脑嗅觉区“记住”这种气味。
核磁共振检查结果显示，志愿者接受轻微电击后，大脑嗅觉区记忆气味功能得到提高。大脑神经“牢记”电击与气味间的联系，因此能更迅速区分两种相似气味。换言之，人类大脑能建立嗅出危险的机制。
研究人员说，这项实验解释了人类能感知危险迫近的原因。史前人类拥有区别不同动物气味的能力，正是在恶劣环境中为生存而进化发展的结果。
科学家早已发现，人类嗅觉与情绪之间有紧密联系。香水味或蛋糕的甜香味能让人回忆起美好往事。相反，机油气味则可能使患有“创伤后应激障碍”的士兵想起战场上的痛苦经历。
研究人员说，经历过厨房火灾的人闻到烟味时，能立即区分是东西烧糊的气味还是普通烟味。
因此，当人们被环境中的各种信息包围时，拥有嗅出危险的能力可以帮助人们敏锐察觉危险的临近。
这项成果刊登在美国3月28日的《科学》杂志上。
生物谷推荐原始出处：
Science 28 March 2008:
Vol. 319. no. 5871, pp. 1842 - 1845
DOI: 10.1126/science.1152837
Aversive Learning Enhances Perceptual and Cortical Discrimination of Indiscriminable Odor Cues
Wen Li,1* James D. Howard,1 Todd B. Parrish,1,2 Jay A. Gottfried1,3,4
Learning to associate sensory cues with threats is critical for minimizing aversive experience. The ecological benefit of associative learning relies on accurate perception of predictive cues, but how aversive learning enhances perceptual acuity of sensory signals, particularly in humans, is unclear. We combined multivariate functional magnetic resonance imaging with olfactory psychophysics to show that initially indistinguishable odor enantiomers (mirror-image molecules) become discriminable after aversive conditioning, paralleling the spatial divergence of ensemble activity patterns in primary olfactory (piriform) cortex. Our findings indicate that aversive learning induces piriform plasticity with corresponding gains in odor enantiomer discrimination, underscoring the capacity of fear conditioning to update perceptual representation of predictive cues, over and above its well-recognized role in the acquisition of conditioned responses. That completely indiscriminable sensations can be transformed into discriminable percepts further accentuates the potency of associative learning to enhance sensory cue perception and support adaptive behavior.
1 Cognitive Neurology and Alzheimer's Disease Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
2 Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
3 Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
4 Department of Psychology, Northwestern University, Evanston, IL 60208, USA.
* To whom correspondence should be addressed. E-mail: wenli@northwestern.edu .
