scholarly journals Reading out olfactory receptors: feedforward circuits detect odors in mixtures without demixing

2016 ◽  
Author(s):  
Alexander Mathis ◽  
Dan Rokni ◽  
Vikrant Kapoor ◽  
Matthias Bethge ◽  
Venkatesh N. Murthy
Keyword(s):  
Olfactory Bulb ◽  
Olfactory System ◽  
Olfactory Receptors ◽  
Sensory Systems ◽  
Neural Mechanisms ◽  
Small Subset ◽  
Nonlinear Interactions ◽  
Decision Boundaries ◽  
Insight Into

The olfactory system, like other sensory systems, can detect specific stimuli of interest amidst complex, varying backgrounds. To gain insight into the neural mechanisms underlying this ability, we imaged responses of mouse olfactory bulb glomeruli to single odors and hundreds of mixtures. We used this data to build a model of mixture responses that incorporated nonlinear interactions and trial-to-trial variability and explored potential decoding mechanisms that can mimic mouse performance from our previous study (Rokni et al., 2014) when given glomerular responses as input. We find that a linear decoder with sparse weights could match mouse performance using just a small subset of the glomeruli (~ 15). However, when such a decoder is trained only with single odors, it generalizes poorly to mixture stimuli due to nonlinear mixture responses. We show that mice similarly fail to generalize, although they could in principle fully decompose the mixtures. This suggests that mice learn this segregation task discriminatively by adjusting task-specific decision boundaries without taking advantage of a demixed representation of odors.

Single Cell Spike Activity in the Olfactory Bulb

1956 ◽  
Vol 186 (2) ◽  
pp. 255-257 ◽  
Author(s):  
Raymond R. Walsh
Keyword(s):  
Olfactory Bulb ◽  
Single Cell ◽  
Spike Activity ◽  
Olfactory System ◽  
Olfactory Receptors ◽  
Class I ◽  
Olfactory Stimulation ◽  
Fundamental Characteristic ◽  
Class Iii ◽  
Discharge Patterns

Studies of single-cell spike discharges in the olfactory bulb of the rabbit indicate the presence of three classes of neurons as characterized by their discharge patterns. Cells of class I discharge continuously and spontaneously; class II cells discharge intermittently in bursts, in synchrony with the passage of air through the nose. Cells of classes I and II are unmodified during olfactory stimulation. It appears there are many cells in the olfactory bulb whose discharge patterns are unrelated to excitation of the olfactory receptors by odors. Cells of class III respond to appropriate odors; the response of such cells to some odors and not others indicates that odor specificity is a fundamental characteristic of the olfactory system.

scholarly journals Extinction reverses olfactory fear-conditioned increases in neuron number and glomerular size

2015 ◽  
Vol 112 (41) ◽  
pp. 12846-12851 ◽  
Author(s):  
Filomene G. Morrison ◽  
Brian G. Dias ◽  
Kerry J. Ressler
Keyword(s):  
Olfactory Bulb ◽  
Learning And Memory ◽  
Olfactory Epithelium ◽  
Olfactory System ◽  
Structural Changes ◽  
Freezing Behavior ◽  
Extinction Training ◽  
Odor Stimulus ◽  
Main Olfactory Epithelium ◽  
Odor Learning

Although much work has investigated the contribution of brain regions such as the amygdala, hippocampus, and prefrontal cortex to the processing of fear learning and memory, fewer studies have examined the role of sensory systems, in particular the olfactory system, in the detection and perception of cues involved in learning and memory. The primary sensory receptive field maps of the olfactory system are exquisitely organized and respond dynamically to cues in the environment, remaining plastic from development through adulthood. We have previously demonstrated that olfactory fear conditioning leads to increased odorant-specific receptor representation in the main olfactory epithelium and in glomeruli within the olfactory bulb. We now demonstrate that olfactory extinction training specific to the conditioned odor stimulus reverses the conditioning-associated freezing behavior and odor learning-induced structural changes in the olfactory epithelium and olfactory bulb in an odorant ligand-specific manner. These data suggest that learning-induced freezing behavior, structural alterations, and enhanced neural sensory representation can be reversed in adult mice following extinction training.

scholarly journals Region-specific amyloid-β accumulation in the olfactory system influences olfactory sensory neuronal dysfunction in 5xFAD mice

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Gowoon Son ◽  
Seung-Jun Yoo ◽  
Shinwoo Kang ◽  
Ameer Rasheed ◽  
Da Hae Jung ◽  
...  
Keyword(s):  
Olfactory Bulb ◽  
Sensory Neurons ◽  
Olfactory System ◽  
Amyloid Β ◽  
Olfactory Sensory Neurons ◽  
Basal Cells ◽  
Irreversible Damage ◽  
5Xfad Mouse ◽  
Peripheral Areas ◽  
5Xfad Mice

Abstract Background Hyposmia in Alzheimer’s disease (AD) is a typical early symptom according to numerous previous clinical studies. Although amyloid-β (Aβ), which is one of the toxic factors upregulated early in AD, has been identified in many studies, even in the peripheral areas of the olfactory system, the pathology involving olfactory sensory neurons (OSNs) remains poorly understood. Methods Here, we focused on peripheral olfactory sensory neurons (OSNs) and delved deeper into the direct relationship between pathophysiological and behavioral results using odorants. We also confirmed histologically the pathological changes in 3-month-old 5xFAD mouse models, which recapitulates AD pathology. We introduced a numeric scale histologically to compare physiological phenomenon and local tissue lesions regardless of the anatomical plane. Results We observed the odorant group that the 5xFAD mice showed reduced responses to odorants. These also did not physiologically activate OSNs that propagate their axons to the ventral olfactory bulb. Interestingly, the amount of accumulated amyloid-β (Aβ) was high in the OSNs located in the olfactory epithelial ectoturbinate and the ventral olfactory bulb glomeruli. We also observed irreversible damage to the ectoturbinate of the olfactory epithelium by measuring the impaired neuronal turnover ratio from the basal cells to the matured OSNs. Conclusions Our results showed that partial and asymmetrical accumulation of Aβ coincided with physiologically and structurally damaged areas in the peripheral olfactory system, which evoked hyporeactivity to some odorants. Taken together, partial olfactory dysfunction closely associated with peripheral OSN’s loss could be a leading cause of AD-related hyposmia, a characteristic of early AD.

scholarly journals Organization and distribution of glomeruli in the bowhead whale olfactory bulb

2014 ◽  
Author(s):  
Takushi Kishida ◽  
J. G. M. Thewissen ◽  
Sharon Usip ◽  
John C George ◽  
Robert S Suydam
Keyword(s):  
Olfactory Bulb ◽  
Olfactory Receptor ◽  
Olfactory Receptors ◽  
Molecular Data ◽  
Dorsal Side ◽  
Bowhead Whale ◽  
Model Organisms ◽  
Marker Genes ◽  
Baleen Whales ◽  
Olfactory Receptor Genes

Although modern baleen whales still possess a functional olfactory systems that includes olfactory bulbs, cranial nerve I and olfactory receptor genes, their olfactory capabilities have been reduced profoundly. This is probably in response to their fully aquatic lifestyle. The glomeruli that occur in the olfactory bulb can be divided into two non-overlapping domains, a dorsal domain and a ventral domain. Recent molecular studies revealed that all modern whales have lost olfactory receptor genes and marker genes that are specific to the dorsal domain, and that a modern baleen whale possess only 60 olfactory receptor genes. Here we show that olfactory bulb of bowhead whales (Balaena mysticetus, Mysticeti) lacks glomeruli on the dorsal side, consistent with the molecular data. In addition, we estimate that there are more than 4,000 glomeruli in the bowhead whale olfactory bulb. Olfactory sensory neurons that express the same olfactory receptor in mice generally project to two specific glomeruli in an olfactory bulb, meaning that ratio of the number of olfactory receptors : the number of glomeruli is approximately 1:2. However, we show here that this ratio is not applicable to whales, indicating the limitation of mice as model organisms for understanding the initial coding of odor information among mammals.

scholarly journals A Mathematical Model of the Olfactory Bulb for the Selective Adaptation Mechanism in the Rodent Olfactory System

PLoS ONE ◽  
2016 ◽  
Vol 11 (12) ◽  
pp. e0165230
Author(s):  
Zu Soh ◽  
Shinya Nishikawa ◽  
Yuichi Kurita ◽  
Noboru Takiguchi ◽  
Toshio Tsuji
Keyword(s):  
Mathematical Model ◽  
Olfactory Bulb ◽  
Olfactory System ◽  
Selective Adaptation ◽  
Adaptation Mechanism

Retronasal Smell

Neuroenology ◽  
2016 ◽  
pp. 128-134
Author(s):  
Gordon M. Shepherd
Keyword(s):  
Olfactory Bulb ◽  
Olfactory Receptors ◽  
Olfactory Cortex ◽  
Initial Experience

We compare the initial experience of the aroma of the wine in the glass with the experience of the retronasal aroma as it contributes to the full flavor of the wine in the mouth and throat. We discuss the controversy over whether retronasal smell is less sensitive than orthonasal smell, and what could be the reasons. The processing of retronasal smell images is described from the olfactory receptors to the olfactory bulb, olfactory cortex, and highest cortical levels.

Autobiographical Memory and the Self-Concept

2020 ◽  
pp. 189-212
Author(s):  
Matthew D. Grilli ◽  
Lee Ryan
Keyword(s):  
Life History ◽  
Autobiographical Memory ◽  
Cognitive Neuroscience ◽  
Neural Mechanisms ◽  
The Self ◽  
Self Concept ◽  
Autobiographical Memories ◽  
Core Self ◽  
Insight Into

Autobiographical memory plays a central role in one’s conceptualization of the self. It does so not only by storing the content of one’s life history, but also by providing the memories that are used to construct who we are and what we hope to become. Based on theories and evidence from cognitive neuroscience, the authors of this chapter discuss the contents and organization of autobiographical memory and the neural mechanisms that support the retrieval of autobiographical memories. They also cover core self-related functions served by this type of memory. The chapter closes by considering how the cognitive neuroscience of autobiographical memory and its self-related functions can provide insight into mechanisms of enduring change.

scholarly journals The role of SNMPs in insect olfaction

2020 ◽  
Author(s):  
Sina Cassau ◽  
Jürgen Krieger
Keyword(s):  
Membrane Proteins ◽  
Olfactory System ◽  
Critical Role ◽  
Olfactory Receptors ◽  
Wide Distribution ◽  
Insect Olfaction ◽  
Survival And Reproduction ◽  
Odorant Binding ◽  
Encoding Genes

AbstractThe sense of smell enables insects to recognize olfactory signals crucial for survival and reproduction. In insects, odorant detection highly depends on the interplay of distinct proteins expressed by specialized olfactory sensory neurons (OSNs) and associated support cells which are housed together in chemosensory units, named sensilla, mainly located on the antenna. Besides odorant-binding proteins (OBPs) and olfactory receptors, so-called sensory neuron membrane proteins (SNMPs) are indicated to play a critical role in the detection of certain odorants. SNMPs are insect-specific membrane proteins initially identified in pheromone-sensitive OSNs of Lepidoptera and are indispensable for a proper detection of pheromones. In the last decades, genome and transcriptome analyses have revealed a wide distribution of SNMP-encoding genes in holometabolous and hemimetabolous insects, with a given species expressing multiple subtypes in distinct cells of the olfactory system. Besides SNMPs having a neuronal expression in subpopulations of OSNs, certain SNMP types were found expressed in OSN-associated support cells suggesting different decisive roles of SNMPs in the peripheral olfactory system. In this review, we will report the state of knowledge of neuronal and non-neuronal members of the SNMP family and discuss their possible functions in insect olfaction.

Phantom Smelling

2002 ◽  
Vol 94 (3) ◽  
pp. 841-850 ◽  
Author(s):  
George Grouios
Keyword(s):  
Neuronal Activity ◽  
Olfactory System ◽  
Olfactory Receptors ◽  
Brain Structures ◽  
Neural Representation ◽  
Olfactory Organ ◽  
Olfactory Perception ◽  
Serious Injury ◽  
Normal Input

A case of phantom smelling (phantosmia) is described in a 28-yr.-old man who developed permanent bilateral anosmia after a serious injury to olfaction-related brain structures at the age of 25 years. The findings indicate that, even years after loss of input from olfactory receptors, the neural representation of olfactory perception can still recreate olfactory sensations without any conscious recall of them. This indicates that the neural representation of olfactory sensations remains functional and implies that neuronal activity in the olfactory organ or in other brain structures gives rise to olfactory experiences perceived as originating from the perception of original odor substances. The report suggests the intriguing possibility that the olfactory perception is not a passive process that merely reflects its normal input from the olfactory system but is continuously generated by a neural representation in the olfactory organ or in other olfaction-related brain structures, based on both genetic and sensory determinants. To the author's knowledge this is the first reported case of its kind.

scholarly journals From Gas Sensors to Biomimetic Artificial Noses

Chemosensors ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 32 ◽  
Author(s):  
Paolo Pelosi ◽  
Jiao Zhu ◽  
Wolfgang Knoll
Keyword(s):  
Gas Sensors ◽  
Olfactory System ◽  
Recent Literature ◽  
State Of The Art ◽  
Olfactory Receptors ◽  
Electronic Circuits ◽  
Gas Detectors ◽  
Extreme Sensitivity ◽  
Novel Approaches ◽  
Human Nose

Since the first attempts to mimic the human nose with artificial devices, a variety of sensors have been developed, ranging from simple inorganic and organic gas detectors to biosensing elements incorporating proteins of the biological olfactory system. In order to design a device able to mimic the human nose, two major issues still need to be addressed regarding the complexity of olfactory coding and the extreme sensitivity of the biological system. So far, only 50 of the approximately 300–400 functioning olfactory receptors have been de-orphanized, still a long way from breaking the human olfactory code. On the other hand, the exceptional sensitivity of the human nose is based on amplification mechanisms difficult to reproduce with electronic circuits, and perhaps novel approaches are required to address this issue. Here, we review the recent literature on chemical sensing both in biological systems and artificial devices, and try to establish the state-of-the-art towards the design of an electronic nose.

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