Olfactory experience shapes the evaluation of odour similarity in ants: a behavioural and computational analysis

Abstract

Perceptual similarity between stimuli is often assessed via generalization, the response to stimuli that are similar to the one which was previously conditioned. Although conditioning procedures are variable, studies on how this variation may affect perceptual similarity remain scarce. Here, we use a combination of behavioural and computational analyses to investigate the influence of olfactory conditioning procedures on odour generalization in ants. Insects were trained following either absolute conditioning, in which a single odour (an aldehyde) was rewarded with sucrose, or differential conditioning, in which one odour (the same aldehyde) was similarly rewarded and another odour (an aldehyde differing in carbon-chain length) was punished with quinine. The response to the trained odours and generalization to other aldehydes were assessed. We show that olfactory similarity, rather than being immutable, varies with the conditioning procedure. Compared with absolute conditioning, differential conditioning enhances olfactory discrimination. This improvement is best described by a multiplicative interaction between two independent processes, the excitatory and inhibitory generalization gradients induced by the rewarded and the punished odour, respectively. We show that olfactory similarity is dramatically shaped by an individual's perceptual experience and suggest a new hypothesis for the nature of stimulus interactions underlying experience-dependent changes in perceptual similarity.

Compounds without borders: A mechanism for quantifying complex odors and responses to scent-pollution in bumblebees

“…Work on ants has shown that previously generalized odor pairs can be discriminated after training with differential conditioning, implying that the behavioral-discrimination measured was contextual [32]. Indeed, the role of experience in generalization behavior has been demonstrated in multiple studies [37,38]. This behaviorallydemonstrated ability to dynamically shift discrimination thresholds in insects has been supported by work showing that learning can modulate neural activity within the antennal lobe [16,17].…”

Aversive learning of odor-heat associations in ants

“…flies; Barth et al, 2014) and learning paradigms (e.g. appetitive conditioning in ants; Perez et al, 2016). It can be explained by the fact that differential conditioning provides a CS− against which the relevant CS+/US association can be contrasted.…”

“…It can be explained by the fact that differential conditioning provides a CS− against which the relevant CS+/US association can be contrasted. A modeling approach showed that the enhanced olfactory discrimination after differential learning is a consequence of the interaction between excitatory and inhibitory generalization gradients mediated by the CS+ and CS− odors (Perez et al, 2016). In free-flying bees trained to associate color stimuli with sucrose reward, colors that appeared to be non-discriminable after absolute conditioning became discriminable after differential conditioning, even if the same rewarded target was used in both conditioning forms (Dyer and Chittka, 2004;Giurfa, 2004).…”

Compounds without borders: a novel paradigm for quantifying complex odors and responses to scent-pollution in bumblebees

“…Work on ants has shown that previously generalized odor pairs can be discriminated after training with differential conditioning, implying that the behavioral-discrimination measured was contextual [29]. Indeed, the role of experience in generalization behavior has been demonstrated in multiple studies [34,35]. This behaviorallydemonstrated ability to dynamically shift discrimination thresholds in insects has been supported by work showing that learning can modulate neural activity within the antennal lobe [16,17].…”