据美国物理学家组织网10月18日（北京时间）报道，哈佛大学神经生物学家培养出一种能“闻”出光线的小鼠，为研究人员更好地理解嗅觉功能的神经机制提供了一种新工具。本周的Nature Neuroscience杂志详述了这项研究，这为未来研究气味和感受之间的关系以及其他感知系统的神经机制开辟了新方向。
要分析大脑的嗅觉感知是如何辨别气味的，最好的方法是研究大脑的活动方式。但气味种类繁多，化学成分非常复杂，变化微细让人难以捉摸，因此追寻这些由嗅觉刺激形成的大脑模式非常困难。
如果让鼻子作为视网膜那会怎么样呢？哈佛大学分子与细胞生物学教授温卡泰斯·默西和冷泉港实验室的同事利用遗传光学技术，把一种光敏蛋白质跟小鼠的嗅觉输入系统结合，培育了一批转基因小鼠，它们的所有嗅觉感受神经元都能表达视网膜素转导通道2（channelrhodopsin-2）蛋白质，这些转基因小鼠的嗅觉路径因此变成由光来激活，代替气味来研究大脑神经细胞如何区别不同气味。
嗅觉信息会在大脑中形成不同的三维空间组织形态，由于光输入很容易被控制，研究人员因此能设计一系列试验，利用光选择性地刺激鼻子里的特定感觉神经，研究大脑中嗅球的激活模式。
默西说，因为用外来光照代替气味在大脑中形成的空间组织只是一种临时性结构，新研究也存在一定的局限，并不能完全解释气味感受能力。研究还显示，在气味被感受的过程中，“嗅闻”的时机起着很大作用。（生物谷Bioon.com）
生物谷推荐英文摘要：
Nature Neuroscience doi:10.1038/nn.2673
Non-redundant odor coding by sister mitral cells revealed by light addressable glomeruli in the mouse
Ashesh K Dhawale, Akari Hagiwara, Upinder S Bhalla, Venkatesh N Murthy & Dinu F Albeanu
Sensory inputs frequently converge on the brain in a spatially organized manner, often with overlapping inputs to multiple target neurons. Whether the responses of target neurons with common inputs become decorrelated depends on the contribution of local circuit interactions. We addressed this issue in the olfactory system using newly generated transgenic mice that express channelrhodopsin-2 in all of the olfactory sensory neurons. By selectively stimulating individual glomeruli with light, we identified mitral/tufted cells that receive common input (sister cells). Sister cells had highly correlated responses to odors, as measured by average spike rates, but their spike timing in relation to respiration was differentially altered. In contrast, non-sister cells correlated poorly on both of these measures. We suggest that sister mitral/tufted cells carry two different channels of information: average activity representing shared glomerular input and phase-specific information that refines odor representations and is substantially independent for sister cells.
