Riffell Jeffrey A, Lei Hong, Christensen Thomas A, Hildebrand John G
University of Arizona, Tucson, 85721, USA.
Curr Biol. 2009 Feb 24;19(4):335-40. doi: 10.1016/j.cub.2009.01.041.
For animals to execute odor-driven behaviors, the olfactory system must process complex odor signals and maintain stimulus identity in the face of constantly changing odor intensities [1-5]. Surprisingly, how the olfactory system maintains identity of complex odors is unclear [6-10]. We took advantage of the plant-pollinator relationship between the Sacred Datura (Datura wrightii) and the moth Manduca sexta[11, 12] to determine how olfactory networks in this insect's brain represent odor mixtures. We combined gas chromatography and neural-ensemble recording in the moth's antennal lobe to examine population codes for the floral mixture and its fractionated components. Although the floral scent of D. wrightii comprises at least 60 compounds, only nine of those elicited robust neural responses. Behavioral experiments confirmed that these nine odorants mediate flower-foraging behaviors, but only as a mixture. Moreover, the mixture evoked equivalent foraging behaviors over a 1000-fold range in dilution, suggesting a singular percept across this concentration range. Furthermore, neural-ensemble recordings in the moth's antennal lobe revealed that reliable encoding of the floral mixture is organized through synchronized activity distributed across a population of glomerular coding units, and this timing mechanism may bind the features of a complex stimulus into a coherent odor percept.
为了使动物能够执行由气味驱动的行为，嗅觉系统必须处理复杂的气味信号，并在气味强度不断变化的情况下保持刺激的特征[1-5]。令人惊讶的是，嗅觉系统如何保持复杂气味的特征尚不清楚[6-10]。我们利用了曼陀罗（Datura wrightii）与烟草天蛾（Manduca sexta）之间的植物-传粉者关系[11, 12]，来确定这种昆虫大脑中的嗅觉网络如何表征气味混合物。我们将气相色谱法与烟草天蛾触角叶中的神经群体记录相结合，以研究花朵混合物及其分离成分的群体编码。尽管曼陀罗的花香包含至少60种化合物，但其中只有9种能引发强烈的神经反应。行为实验证实，这9种气味剂介导了花朵觅食行为，但仅作为一种混合物时才起作用。此外，该混合物在1000倍的稀释范围内能引发同等的觅食行为，这表明在这个浓度范围内存在单一的感知。此外，烟草天蛾触角叶中的神经群体记录显示，花朵混合物的可靠编码是通过分布在一群肾小球编码单元上的同步活动来组织的，并且这种时间机制可能将复杂刺激的特征绑定成一个连贯的气味感知。
