Animals encounter information from different resources simultaneously, integrating input from multiple sensory systems before responding behaviorally. When different cues interact with one another, they may enhance, diminish, or have no impact on their responses. In this project, we test how the presence of chemical cues affect the perception of visual cues. Zebrafish (Danio rerio) often use both chemical cues and visual cues to communicate with shoal mates, to assess predation risk, and to locate food. For example, zebrafish rely on both olfactory cues and visual cues for kin recognition, and they frequently use both chemical and visual cues to search for and to capture prey. In zebrafish, the terminal nerve (TN) constitutes the olfacto-visual centrifugal pathway and connects the olfactory bulb with the retina, thus allowing olfactory perception also to activate visual receptors. Past studies have found that the presence of an olfactory cue can modulate visual sensitivity in zebrafish through the terminal nerve pathway. Alternatively, given that zebrafish are highly social, the presence of social chemical cues may distract individuals from responding to other visual cues, such as food and predator visual cues. Foraging and predator chemical cues, including chemical food cues and alarm cues, may also distract individuals from responding to non-essential visual cues. Here, we test whether the response to a visual cue either increases or decreases when presented in concert with alanine, an amino acid that represents the olfactory cues of zebrafish prey. We found that the presence of chemical cues did not affect whether zebrafish responded to visual cues, but that the fish took longer to respond to visual cues when chemical cues were also present. These findings suggest that different aspects of behavior could be affected by the interaction between sensory modalities. We also found that this impact of delayed response was significant only when the visual cue<br/>was weak compared to the strength of the chemical cue, suggesting that the salience of interacting cues may also have an influence on determining the outcomes of the interactions. Overall, the interactive effects of chemicals on an animal’s response to visual cues may also have wide-ranging impacts on behavior including foraging, mating, and evading predators, and the interaction of cues may affect different aspects of the same behavior.

Insects are able to navigate their environments because they can detect hydrocarbons and volatile odors, but it is not clear which one has the fastest reaction when detected, or how much of a response can be produced due to either one. In order to determine which category of odorant is detected first as well as which one causes the highest response rate, data on electrophysiological responses from ants was analyzed. While the statistical tests can be done to understand and answer the questions raised by the study, there are various hydrocarbons and volatile odors that were not used in the data. Conclusive evidence only applies to the odorants used in the experiments.

Enantiomers are pairs of non-superimposable mirror-image molecules. One molecule in the pair is the clockwise version (+) while the other is the counterclockwise version (-). Some pairs have divergent odor qualities, e.g. L-carvone (“spearmint”) vs. D-carvone (“caraway”), while other pairs do not. Existing theory about the origin of such differences is largely qualitative (Friedman and Miller, 1971; Bentley, 2006; Brookes et al., 2008). While quantitative models based on intrinsic molecular features predict some structure–odor relationships (Keller et al., 2017), they cannot identify, e.g. the more intense enantiomer in a pair; the mathematical operations underlying such features are invariant under symmetry (Shadmany et al., 2018). Only the olfactory receptor (OR) can break this symmetry because each molecule within an enantiomeric pair will have a different binding configuration with a receptor. However, features that predict odor divergence within a pair may be identifiable; for example, six-membered ring flexibility has been offered as a candidate (Brookes et al., 2008). To address this problem, we collected detection threshold data for >400 molecules (organized into enantiomeric pairs) from a variety of public data sources and academic literature. From each pair, we computed the within-pair divergence in odor detection threshold, as well as Mordred descriptors (molecular features derived from the structure of a molecule) and Morgan fingerprints (mathematical representations of molecule structure). While these molecular features are identical within-pair (due to symmetry), they remain distinct across pairs. The resulting structure+perception dataset was used to build a predictive model of odor detection threshold divergence. It predicted a modest fraction of variance in odor detection threshold divergence (r 2 ~ 0.3 in cross-validation). We speculate that most of the remaining variance could be explained by a better understanding of the ligand-receptor binding process.