Component Information Is Preserved in Glomerular Responses to Binary Odor Mixtures in the Moth Spodoptera littoralis

Abstract

Natural odors are often complex mixtures of different compounds. These mixtures can be perceived to have qualities that are different from their components. Moreover, components can be difficult to distinguish within a blend, even if those components are identifiable when presented individually. Thus, odor components can interact along the olfactory pathway in a nonlinear fashion such that the mixture is not perceived simply as the sum of its components. Here we investigated odor-evoked changes in Ca2+ concentration to binary blends of plant-related substances in individually identified glomeruli in the moth Spodoptera littoralis. We used a wide range of blend ratios and a range of concentrations below the level at which glomerular responses become saturated. We found no statistically significant cases where the mixture response was greater than both component responses at the same total concentration (synergistic interactions) and no statistically significant cases where the mixture response was less than either component presented individually (suppressive interactions). Therefore, we conclude that, for the plant mixtures studied, information of their components is preserved in the neural representations encoded at the first stage of olfactory processing in this moth species.

Antennal Lobe Processing Correlates to Moth Olfactory Behavior

“…This is in agreement with previous insect studies ( Deisig et al, 2006;Carlsson et al, 2007;Silbering and Galizia, 2007). However, at the output level, strong nonlinear interactions that could not be predicted from the single component patterns occurred in six of seven animals, even when controlling for concentration (see Materials and Methods, Optophysiology, Odor stimulation).…”

Coding and interaction of sex pheromone and plant volatile signals in the antennal lobe of the codling moth Cydia pomonella

“…Mixture interactions between general odours are known from other moth species (Carlsson et al, 2007;Namiki et al, 2008;Piñero et al, 2008), and we found consistent effects in male and female AL neurons to the mixture of pear ester and acetic acid, which has been shown to be behaviourally synergistic in both sexes (Landolt et al, 2007).…”

Compound valence is conserved in binary odor mixtures in Drosophila melanogaster

“…Furthermore, olfactory information is significantly modulated by a dense network of local neurons in the first olfactory center of the insect brain, the antennal lobe (AL) (reviewed in Galizia and Rössler, 2010;Masse et al, 2009;Wilson, 2013;Wilson and Mainen, 2006). Nevertheless, physiological odor mixture responses in the AL are qualitatively predictable on the basis of mixture constituent responses in Drosophila (Olsen et al, 2010;Silbering and Galizia, 2007) and other insects (Carlsson et al, 2007;Deisig et al, 2006;Deisig et al, 2010;Fernandez et al, 2009;Joerges et al, 1997;Stierle et al, 2013; but see Anton and Hansson, 1996;Kuebler et al, 2011;Kuebler et al, 2012;Meyer and Galizia, 2012). Therefore, if single OSN class responses are already behaviorally meaningful, the innate hedonic valence of odor mixtures may in fact be predictable on the basis of the valences of mixture constituents.…”