Data from: Odourant dominance in olfactory mixture processing: what makes a strong odourant

The question of how animals process stimulus mixtures remains controversial as opposing views propose that mixtures are processed analytically, as the sum of their elements, or holistically, as unique entities different from their elements. Overshadowing is a widespread phenomenon that can help decide between these alternatives. In overshadowing, an individual trained with a binary mixture learns one element better at the expense of the other. Although element salience (learning success) has been suggested as a main explanation for overshadowing, the mechanisms underlying this phenomenon remain unclear. We studied olfactory overshadowing in honeybees to uncover the mechanisms underlying olfactory-mixture processing. We provide, to our knowledge, the most comprehensive dataset on overshadowing to date based on 90 experimental groups involving more than 2700 bees trained either with six odourants or with their resulting 15 binary mixtures. We found that bees process olfactory mixtures analytically and that salience alone cannot predict overshadowing. After normalizing learning success, we found that an unexpected feature, the generalization profile of an odourant, was determinant for overshadowing. Odourants that induced less generalization enhanced their distinctiveness and became dominant in the mixture. Our study thus uncovers features that determine odourant dominance within olfactory mixtures and allows the referring of this phenomenon to differences in neural activity both at the receptor and the central level in the insect nervous system.

动物如何处理刺激混合物的问题至今仍存在争议，对立观点分别认为，混合物会被以分析式处理——即作为其组成成分的总和，或是以整体式处理——即作为不同于组成成分的独特实体。遮蔽效应（overshadowing）是一种广泛存在的现象，可用于在这两种观点间做出判断。在遮蔽效应中，接受二元混合物训练的个体，能够以牺牲另一成分的学习效果为代价，更好地习得其中一种成分。尽管已有研究提出成分显著性（即学习成功率）是遮蔽效应的主要解释，但该现象背后的机制仍不明确。我们以蜜蜂为研究对象，探究其嗅觉遮蔽效应，以揭示嗅觉混合物处理的内在机制。据我们所知，本研究基于90个实验组、涉及超过2700只蜜蜂的实验数据，是目前为止最为全面的遮蔽效应数据集：这些蜜蜂分别接受了6种气味剂（odourants），或是由其组合形成的15种二元混合物的训练。我们发现，蜜蜂对嗅觉混合物采用分析式处理方式，且仅靠成分显著性无法预测遮蔽效应的发生。在对学习成功率进行标准化处理后，我们发现一项意外的特征——气味剂的泛化轮廓（generalization profile）才是决定遮蔽效应的关键因素。泛化程度较低的气味剂能够提升自身的独特性，进而在混合物中占据主导地位。综上，本研究揭示了决定嗅觉混合物中气味剂主导地位的关键特征，并将该现象归因于昆虫神经系统中受体及中枢层面的神经活动差异。