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Proc Biol Sci. 2015 Mar 7;282(1802). pii: 20142562. doi: 10.1098/rspb.2014.2562.

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

Author information

1
Research Center on Animal Cognition, Université de Toulouse, 118 Route de Narbonne, Toulouse Cedex 9 31062, France Research Center on Animal Cognition, CNRS, 118 Route de Narbonne, Toulouse Cedex 9 31062, France.
2
Research Center on Animal Cognition, Université de Toulouse, 118 Route de Narbonne, Toulouse Cedex 9 31062, France Research Center on Animal Cognition, CNRS, 118 Route de Narbonne, Toulouse Cedex 9 31062, France Evolution Genomes and Speciation Lab, UPR 9034, CNRS, Avenue de la Terrasse, Bâtiment 13, Boite Postale 1, Gif sur Yvette 91198, France.
3
Department of Biology, University of Konstanz, Konstanz 78457, Germany.
4
Research Center on Animal Cognition, Université de Toulouse, 118 Route de Narbonne, Toulouse Cedex 9 31062, France Research Center on Animal Cognition, CNRS, 118 Route de Narbonne, Toulouse Cedex 9 31062, France martin.giurfa@univ-tlse3.fr.

Abstract

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.

KEYWORDS:

honeybees; mixture processing; odourant dominance; olfaction; olfactory learning; overshadowing

PMID:
25652840
PMCID:
PMC4344151
DOI:
10.1098/rspb.2014.2562
[Indexed for MEDLINE]
Free PMC Article

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