scholarly journals Front-end Weber-Fechner gain control enhances the fidelity of combinatorial odor coding

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Nirag Kadakia ◽  
Thierry Emonet
Keyword(s):  
Gain Control ◽  
Feedback Mechanism ◽  
Olfactory Receptor Neurons ◽  
Receptor Sensitivity ◽  
Adaptation Mechanism ◽  
Odor Coding ◽  
Front End ◽  
Receptor Neurons ◽  
Odor Classification ◽  
Odor Signals

We showed previously (Gorur-Shandilya et al., 2017) that Drosophila olfactory receptor neurons (ORNs) expressing the co-receptor Orco scale their gain inversely with mean odor intensity according to Weber-Fechner’s law. Here, we show that this front-end adaptation promotes the reconstruction of odor identity from dynamic odor signals, even in the presence of confounding background odors and rapid intensity fluctuations. These enhancements are further aided by known downstream transformations in the antennal lobe and mushroom body. Our results, which are applicable to various odor classification and reconstruction schemes, stem from the fact that this adaptation mechanism is not intrinsic to the identity of the receptor involved. Instead, a feedback mechanism adjusts receptor sensitivity based on the activity of the receptor-Orco complex, according to Weber-Fechner’s law. Thus, a common scaling of the gain across Orco-expressing ORNs may be a key feature of ORN adaptation that helps preserve combinatorial odor codes in naturalistic landscapes.

scholarly journals Front-end Weber-Fechner gain control enhances the fidelity of combinatorial odor coding

2018 ◽  
Author(s):  
Nirag Kadakia ◽  
Thierry Emonet
Keyword(s):  
Scaling Law ◽  
Gain Control ◽  
Vital Role ◽  
Biophysical Model ◽  
Natural Environments ◽  
Odor Coding ◽  
Tuning Curves ◽  
Front End ◽  
Receptor Neurons ◽  
Odor Signals

Odor identity is encoded by spatiotemporal patterns of activity in olfactory receptor neurons (ORNs). In natural environments, the intensity and timescales of odor signals can span several orders of magnitude, and odors can mix with one another, potentially scrambling the combinatorial code mapping neural activity to odor identity. Recent studies have shown that inDrosophila melanogasterthe ORNs that express the olfactory co-receptor Orco scale their gain inversely with mean odor concentration according to the Weber-Fechner Law of psychophysics. Here we use a minimal biophysical model of signal transduction, ORN firing, and signal decoding to investigate the implications of this front-end scaling law for the neural representations of odor identity. We find that Weber-Fechner scaling enhances coding capacity and promotes the reconstruction of odor identity from dynamic odor signals, even in the presence of confounding background odors and rapid intensity fluctuations. We show that these enhancements are further aided by downstream transformations in the antennal lobe and mushroom body. Thus, despite the broad overlap between individual ORN tuning curves, a mechanism of front-end adaptation, when endowed with Weber-Fechner scaling, may play a vital role in preserving representations of odor identity in naturalistic odor landscapes.

scholarly journals An update on anatomy and function of the teleost olfactory system

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7808 ◽  
Author(s):  
Jesús Olivares ◽  
Oliver Schmachtenberg
Keyword(s):  
Olfactory System ◽  
Olfactory Receptor Neurons ◽  
Odorant Receptors ◽  
Odor Coding ◽  
Animal Group ◽  
Different Types ◽  
Olfactory Systems ◽  
Receptor Neurons ◽  
Olfactory Organs ◽  
And Function

About half of all extant vertebrates are teleost fishes. Although our knowledge about anatomy and function of their olfactory systems still lags behind that of mammals, recent advances in cellular and molecular biology have provided us with a wealth of novel information about the sense of smell in this important animal group. Its paired olfactory organs contain up to five types of olfactory receptor neurons expressing OR, TAAR, VR1- and VR2-class odorant receptors associated with individual transduction machineries. The different types of receptor neurons are preferentially tuned towards particular classes of odorants, that are associated with specific behaviors, such as feeding, mating or migration. We discuss the connections of the receptor neurons in the olfactory bulb, the differences in bulbar circuitry compared to mammals, and the characteristics of second order projections to telencephalic olfactory areas, considering the everted ontogeny of the teleost telencephalon. The review concludes with a brief overview of current theories about odor coding and the prominent neural oscillations observed in the teleost olfactory system.

scholarly journals Calcium-activated chloride channels clamp odor-evoked spike activity in olfactory receptor neurons

2018 ◽  
Author(s):  
Joseph D. Zak ◽  
Julien Grimaud ◽  
Rong-Chang Li ◽  
Chih-Chun Lin ◽  
Venkatesh N. Murthy
Keyword(s):  
Olfactory Receptor ◽  
Chloride Channels ◽  
Feedback Mechanism ◽  
Olfactory Receptor Neurons ◽  
Odor Source ◽  
Wild Type ◽  
Behavioral Deficits ◽  
Receptor Neurons

AbstractThe calcium-activated chloride channel anoctamin-2 (Ano2) is thought to amplify transduction currents in ORNs, a hypothesis supported by previous studies in dissociated neurons from Ano2-/- mice. Paradoxically, despite a reduction in transduction currents in Ano2-/- ORNs, their spike output for odor stimuli may be higher. We examined the role of Ano2 in ORNs in their native environment in freely breathing mice by imaging activity in ORN axons as they arrive in the olfactory bulb glomeruli. Odor-evoked responses in ORN axons of Ano2-/- mice were consistently larger for a variety of odorants and concentrations. In an open arena, Ano2-/- mice took longer to approach a localized odor source than wild-type mice, revealing clear olfactory behavioral deficits. Our studies provide the first in vivo evidence toward an alternative role for Ano2 in the olfactory transduction cascade, where it may serve as a feedback mechanism to clamp ORN spike output.

scholarly journals High Precision of Spike Timing across Olfactory Receptor Neurons Allows Rapid Odor Coding in Drosophila

iScience ◽  
2018 ◽  
Vol 4 ◽  
pp. 76-83 ◽  
Author(s):  
Alexander Egea-Weiss ◽  
Alpha Renner ◽  
Christoph J. Kleineidam ◽  
Paul Szyszka
Keyword(s):  
High Precision ◽  
Olfactory Receptor ◽  
Spike Timing ◽  
Olfactory Receptor Neurons ◽  
Odor Coding ◽  
Receptor Neurons

scholarly journals Olfactory receptor neurons use gain control and complementary kinetics to encode intermittent odorant stimuli

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Srinivas Gorur-Shandilya ◽  
Mahmut Demir ◽  
Junjiajia Long ◽  
Damon A Clark ◽  
Thierry Emonet
Keyword(s):  
Olfactory Receptor ◽  
Gain Control ◽  
Olfactory Receptor Neurons ◽  
Kinetic Properties ◽  
Odor Plume ◽  
Spike Generation ◽  
Olfactory Responses ◽  
Mean And Variance ◽  
Receptor Neurons

Insects find food and mates by navigating odorant plumes that can be highly intermittent, with intensities and durations that vary rapidly over orders of magnitude. Much is known about olfactory responses to pulses and steps, but it remains unclear how olfactory receptor neurons (ORNs) detect the intensity and timing of natural stimuli, where the absence of scale in the signal makes detection a formidable olfactory task. By stimulating Drosophila ORNs in vivo with naturalistic and Gaussian stimuli, we show that ORNs adapt to stimulus mean and variance, and that adaptation and saturation contribute to naturalistic sensing. Mean-dependent gain control followed the Weber-Fechner relation and occurred primarily at odor transduction, while variance-dependent gain control occurred at both transduction and spiking. Transduction and spike generation possessed complementary kinetic properties, that together preserved the timing of odorant encounters in ORN spiking, regardless of intensity. Such scale-invariance could be critical during odor plume navigation.

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