Mixture and odorant processing in the olfactory systems of insects: a comparative perspective

Abstract

Natural olfactory stimuli are often complex mixtures of volatiles, of which the identities and ratios of constituents are important for odor-mediated behaviors. Despite this importance, the mechanism by which the olfactory system processes this complex information remains an area of active study. In this review, we describe recent progress in how odorants and mixtures are processed in the brain of insects. We use a comparative approach toward contrasting olfactory coding and the behavioral efficacy of mixtures in different insect species, and organize these topics around four sections: (1) Examples of the behavioral efficacy of odor mixtures and the olfactory environment; (2) mixture processing in the periphery; (3) mixture coding in the antennal lobe; and (4) evolutionary implications and adaptations for olfactory processing. We also include pertinent background information about the processing of individual odorants and comparative differences in wiring and anatomy, as these topics have been richly investigated and inform the processing of mixtures in the insect olfactory system. Finally, we describe exciting studies that have begun to elucidate the role of the processing of complex olfactory information in evolution and speciation.

Olfactory biosensor for insect semiochemicals analysis by impedance sensing of odorant-binding proteins on interdigitated electrodes

“…However, 4-allylveratrole and butanedione, which respectively belong to ethers and small soluble ketones, could not lead obvious conformation changes of the proteins. The results were in accord with the behavior researches of the insects (Clifford and Riffell, 2013). Therefore, with the prominent chemosensory abilities of the proteins, this OBPs-based impedance biosensor that made full use of the conformational change properties could provide an easy, rapid and sensitive approach for chemicals detection and analysis.…”

“…Among the thousands insects species, most of them have an enormous impact on global agriculture as pests and on public health as disease vectors. Adapted to an ever changing chemosensory world for survival, except for optesthesia, their specialized olfaction was highly evolved to sensitively and specifically detect semiochemicals in the natural world (Carey and Carlson, 2011;Clifford and Riffell, 2013;Schott et al, 2013).…”

Identification of olfactory receptor neurons in Uraba lugens (Lepidoptera: Nolidae) and its implications for host range

“…In moths, specialized ORNs appear to accommodate the recognition of specific blend ratios, which is enhanced by the co-compartmentalization of ORNs (Baker et al, 1998;Quero et al, 2001;Heinbockel et al, 2004;Clifford and Riffell, 2013). Phytophagous insects detect volatile compounds using a set of differentially tuned olfactory receptor neurons (ORNs) mostly present in the antennae.…”

Olfactory Disruption

“…3). 128 After detection but before perception, the circuits processing primary odor information reveal target pathways that gate behaviors like host seeking. While repellents do not directly target second-and third-order neurons associated with olfaction, the function of higher brain centers may indicate which ORNs (upstream signals) are most important.…”