Functional Characteristics of a Tiny but Specialized Olfactory System: Olfactory Receptor Neurons of Carrot Psyllids (Homoptera: Triozidae)

The present study investigates a network model for implementing concentration-invariant representation for odors in the olfactory system. The network consists of olfactory receptor neurons, projection neurons, and inhibitory local neurons. Receptor neurons send excitatory inputs to projection neurons, which are modulated by the inhibitory inputs from local neurons. The modulation occurs at the presynaptic site from a receptor neuron to a projection one, leading to the operation of divisive normalization. The responses of local interneurons are determined by the total activities of olfactory receptor neurons. We find that with a proper parameter condition, the responses of projection neurons become effectively independent of the odor concentration. Simulation results confirm our theoretical analysis.

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Olfactory coding in the turbulent realm

10.1101/179085 ◽

2017 ◽

Author(s):

Vincent Jacob ◽

Christelle Monsempès ◽

Jean-Pierre Rospars ◽

Jean-Baptiste Masson ◽

Philippe Lucas

Keyword(s):

White Noise ◽

Firing Rate ◽

Olfactory Receptor ◽

Olfactory System ◽

Time Course ◽

Temporal Structure ◽

Olfactory Receptor Neurons ◽

Odor Source ◽

Long Distance ◽

Receptor Neurons

AbstractLong-distance olfactory search behaviors depend on odor detection dynamics. Due to turbulence, olfactory signals travel as bursts of variable concentration and spacing and are characterized by long-tail distributions of odor/no-odor events, challenging the computing capacities of olfactory systems. How animals encode complex olfactory scenes to track the plume far from the source remains unclear. Here we focus on the coding of the plume temporal dynamics in moths. We compare responses of olfactory receptor neurons (ORNs) and antennal lobe projection neurons (PNs) to sequences of pheromone stimuli either with white-noise patterns or with realistic turbulent temporal structures simulating a large range of distances (8 to 64 m) from the odor source. For the first time, we analyze what information is extracted by the olfactory system at large distances from the source. Neuronal responses are analyzed using linear–nonlinear models fitted with white-noise stimuli and used for predicting responses to turbulent stimuli. We found that neuronal firing rate is less correlated with the dynamic odor time course when distance to the source increases because of improper coding during long odor and no-odor events that characterize large distances. Rapid adaptation during long puffs does not preclude however the detection of puff transitions in PNs. Individual PNs but not individual ORNs encode the onset and offset of odor puffs for any temporal structure of stimuli. A higher spontaneous firing rate coupled to an inhibition phase at the end of PN responses contributes to this coding property. This allows PNs to decode the temporal structure of the odor plume at any distance to the source, an essential piece of information moths can use in their tracking behavior.Author SummaryLong-distance olfactory search is a difficult task because atmospheric turbulence erases global gradients and makes the plume discontinuous. The dynamics of odor detections is the sole information about the position of the source. Male moths successfully track female pheromone plumes at large distances. Here we show that the moth olfactory system encodes olfactory scenes simulating variable distances from the odor source by characterizing puff onsets and offsets. A single projection neuron is sufficient to provide an accurate representation of the dynamic pheromone time course at any distance to the source while this information seems to be encoded at the population level in olfactory receptor neurons.

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Non-synaptic interactions between olfactory receptor neurons, a possible key feature of odor processing in insects

10.1101/2020.07.23.217216 ◽

2020 ◽

Author(s):

Mario Pannunzi ◽

Thomas Nowotny

Keyword(s):

Lateral Inhibition ◽

Olfactory Receptor ◽

Olfactory System ◽

Antennal Lobe ◽

Olfactory Receptor Neurons ◽

Inhibition Mechanism ◽

Alternative Mechanism ◽

Odor Processing ◽

Synaptic Interactions ◽

Receptor Neurons

AbstractWhen flies explore their environment, they encounter odors in complex, highly intermittent plumes. To navigate a plume and, for example, find food, flies must solve several tasks, including reliably identifying mixtures of odorants and discriminating odorant mixtures emanating from a single source from odorants emitted from separate sources and mixing in the air. Lateral inhibition in the antennal lobe is commonly understood to help solving these two tasks. With a computational model of the Drosophila olfactory system, we analyze the utility of an alternative mechanism for solving them: Non-synaptic (“ephaptic”) interactions (NSIs) between olfactory receptor neurons that are stereotypically co-housed in the same sensilla. For both tasks, NSIs improve the insect olfactory system and outperform the standard lateral inhibition mechanism in the antennal lobe. These results shed light, from an evolutionary perspective, on the role of NSIs, which are normally avoided between neurons, for instance by myelination.

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What the fly’s nose tells the fly’s brain

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1510103112 ◽

2015 ◽

Vol 112 (30) ◽

pp. 9460-9465 ◽

Cited By ~ 43

Author(s):

Charles F. Stevens

Keyword(s):

Olfactory Receptor ◽

Olfactory System ◽

Small Population ◽

Olfactory Receptor Neurons ◽

Small Subset ◽

Second Stage ◽

The Third ◽

Third Stage ◽

Three Layer Architecture ◽

Receptor Neurons

The fly olfactory system has a three-layer architecture: The fly’s olfactory receptor neurons send odor information to the first layer (the encoder) where this information is formatted as combinatorial odor code, one which is maximally informative, with the most informative neurons firing fastest. This first layer then sends the encoded odor information to the second layer (decoder), which consists of about 2,000 neurons that receive the odor information and “break” the code. For each odor, the amplitude of the synaptic odor input to the 2,000 second-layer neurons is approximately normally distributed across the population, which means that only a very small fraction of neurons receive a large input. Each odor, however, activates its own population of large-input neurons and so a small subset of the 2,000 neurons serves as a unique tag for the odor. Strong inhibition prevents most of the second-stage neurons from firing spikes, and therefore spikes from only the small population of large-input neurons is relayed to the third stage. This selected population provides the third stage (the user) with an odor label that can be used to direct behavior based on what odor is present.

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Carnosine synthase deficiency is compatible with normal skeletal muscle and olfactory function but causes reduced olfactory sensitivity in aging mice

Journal of Biological Chemistry ◽

10.1074/jbc.ra120.014188 ◽

2020 ◽

Vol 295 (50) ◽

pp. 17100-17113

Author(s):

Lihua Wang-Eckhardt ◽

Asisa Bastian ◽

Tobias Bruegmann ◽

Philipp Sasse ◽

Matthias Eckhardt

Keyword(s):

Skeletal Muscle ◽

Antioxidant Activity ◽

Muscle Contraction ◽

Olfactory Receptor ◽

Olfactory System ◽

Physiological Role ◽

Olfactory Receptor Neurons ◽

Olfactory Sensitivity ◽

Receptor Neurons ◽

Deficient Mice

Carnosine (β-alanyl-l-histidine) and anserine (β-alanyl-3-methyl-l-histidine) are abundant peptides in the nervous system and skeletal muscle of many vertebrates. Many in vitro and in vivo studies demonstrated that exogenously added carnosine can improve muscle contraction, has antioxidant activity, and can quench various reactive aldehydes. Some of these functions likely contribute to the proposed anti-aging activity of carnosine. However, the physiological role of carnosine and related histidine-containing dipeptides (HCDs) is not clear. In this study, we generated a mouse line deficient in carnosine synthase (Carns1). HCDs were undetectable in the primary olfactory system and skeletal muscle of Carns1-deficient mice. Skeletal muscle contraction in these mice, however, was unaltered, and there was no evidence for reduced pH-buffering capacity in the skeletal muscle. Olfactory tests did not reveal any deterioration in 8-month-old mice lacking carnosine. In contrast, aging (18–24-month-old) Carns1-deficient mice exhibited olfactory sensitivity impairments that correlated with an age-dependent reduction in the number of olfactory receptor neurons. Whereas we found no evidence for elevated levels of lipoxidation and glycation end products in the primary olfactory system, protein carbonylation was increased in the olfactory bulb of aged Carns1-deficient mice. Taken together, these results suggest that carnosine in the olfactory system is not essential for information processing in the olfactory signaling pathway but does have a role in the long-term protection of olfactory receptor neurons, possibly through its antioxidant activity.

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