Principles of odor coding in vertebrates and artificial chemosensory systems

Abstract

The biological olfactory system is the sensory system responsible for the detection of the chemical composition of the environment. Several attempts to mimic biological olfactory systems have led to various artificial olfactory systems using different technical approaches. Here we provide a parallel description of biological olfactory systems and their technical counterparts. We start with a presentation of the input to the systems, the stimuli, and treat the interface between the external world and the environment where receptor neurons or artificial chemosensors reside. We then delineate the functions of receptor neurons and chemosensors as well as their overall I-O relationships. Up to this point, our account of the systems goes along similar lines. The next processing steps differ considerably: while in biology the processing step following the receptor neurons is the "integration" and "processing" of receptor neuron outputs in the olfactory bulb, this step has various realizations in electronic noses. For a long period of time, the signal processing stages beyond the olfactory bulb, i.e., the higher olfactory centers were little studied. Only recently there has been a marked growth of studies tackling the information processing in these centers. In electronic noses, a third stage of processing has virtually never been considered. In this review, we provide an up-to-date overview of the current knowledge of both fields and, for the first time, attempt to tie them together. We hope it will be a breeding ground for better information, communication, and data exchange between very related but so far little connected fields.

Network formation and reorganization of the olfactory system of Xenopus laevis

“…Odorants are made up of highly varied molecular features, or sets of features, that can be perceived as an odor. These "inputs", unlike with other sensory systems (like the auditory and visual system), do not vary along any single parameter (Manzini et al, 2022). They are detected by highly specialized odorant receptor proteins that have varying affinities to specific molecular properties (Manzini et al, 2022).…”

“…The sense of smell, or olfaction, is a form of chemosensation, in which molecular features from the external environment, called odorants, are detected and interpreted by the olfactory system (Farbman, 1992). The olfactory system is responsible for recognizing an almost infinite number of odorants that do not vary across any single parameter (Manzini et al, 2022). A range of what is visible or audible, for example, can be defined by the frequency and intensity of wavelengths (Bushdid et al, 2014), whereas a range of what can be perceived as an odor is much more difficult to define (Manzini et al, 2022).…”

“…The olfactory system is responsible for recognizing an almost infinite number of odorants that do not vary across any single parameter (Manzini et al, 2022). A range of what is visible or audible, for example, can be defined by the frequency and intensity of wavelengths (Bushdid et al, 2014), whereas a range of what can be perceived as an odor is much more difficult to define (Manzini et al, 2022).…”

“…Although the input is hugely varied, across different environments and species, olfactory systems across phyla are highly conserved in regards to anatomy, organization and function (Hildebrand and Shepherd, 1997;Gelperin, 1999;Eisthen, 2002;Ache and Young, 2005). They are composed of a neuronal network made up of neuroepithelial regions that reside within the peripheral nervous system, that connect with olfactory processing and relay centers in the central nervous system (Manzini et al, 2022). The processing of odorants lead to the regulation of physiological and behavioral changes essential for survival and reproduction (Ache and Young, 2005;Manzini et al, 2022).…”

“…They are composed of a neuronal network made up of neuroepithelial regions that reside within the peripheral nervous system, that connect with olfactory processing and relay centers in the central nervous system (Manzini et al, 2022). The processing of odorants lead to the regulation of physiological and behavioral changes essential for survival and reproduction (Ache and Young, 2005;Manzini et al, 2022).…”