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（stimulus mixtures）这一问题迄今仍存在争议，对立观点主要分为两类：一类认为混合物以分析式方式被处理，即视作其组成成分的总和；另一类则认为混合物以整体式方式被处理，即视作不同于组成成分的独特实体。 掩蔽效应（overshadowing）是一种广泛存在的现象，可用于在这两种假说间作出判断。在掩蔽效应中，接受二元混合物（binary mixture）训练的个体，会以牺牲另一成分的学习效果为代价，更高效地习得其中一个成分。尽管成分显著性（即学习成功率）被认为是掩蔽效应的核心解释之一，但该现象背后的具体机制仍不明确。 我们以蜜蜂为研究对象，通过探究其嗅觉掩蔽效应来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组实验构建了目前最为全面的掩蔽效应数据集，共涉及超过2700只蜜蜂，这些蜜蜂分别接受了6种气味剂（odourant）或其组合而成的15种二元混合物的训练。研究结果表明，蜜蜂以分析式方式处理嗅觉混合物，且仅靠成分显著性无法预测掩蔽效应的发生。 在对学习成功率进行标准化处理后，我们发现一个意料之外的关键影响因素——气味剂的泛化轮廓（generalization profile）。泛化程度较低的气味剂能够提升自身的辨识度，进而在混合物中占据主导地位。因此，本研究揭示了决定嗅觉混合物中气味剂主导地位的特征，并将这一现象归因于昆虫神经系统中受体水平与中枢水平的神经活动差异。