scholarly journals ODOR IDENTITY CAN BE EXTRACTED FROM THE RECIPROCAL CONNECTIVITY BETWEEN OLFACTORY BULB AND PIRIFORM CORTEX IN HUMANS

2021 ◽  
Author(s):  
Behzad Iravani ◽  
Artin Arshamian ◽  
Mikael Lundqvist ◽  
Leslie M Kay ◽  
Donald A Wilson ◽  
...  
Keyword(s):  
Olfactory Bulb ◽  
Information Flow ◽  
Information Exchange ◽  
Olfactory System ◽  
Critical Role ◽  
Piriform Cortex ◽  
Brain Regions ◽  
Oscillatory Circuit ◽  
Healthy Human ◽  
Gamma Frequency

Neuronal oscillations route external and internal information across brain regions. In the olfactory system, the two central nodes-the olfactory bulb (OB) and the piriform cortex (PC)-communicate with each other via neural oscillations to shape the olfactory percept. Communication between these nodes have been well characterized in non-human animals but less is known about their role in the human olfactory system. Using a recently developed and validated EEG-based method to extract signals from the OB and PC sources, we show in healthy human participants that there is a bottom-up information flow from the OB to the PC in the beta and gamma frequency bands, while top-down information from the PC to the OB is facilitated by delta and theta oscillations. Importantly, we demonstrate that there was enough in-formation to decipher odor identity above chance from the low gamma in the OB-PC oscillatory circuit as early as 100ms after odor onset. These data further our understanding of the critical role of bidirectional information flow in human sensory systems to produce perception. However, future studies are needed to determine what specific odor information is extracted and communicated in the information exchange.

From the periphery to the brain: Wiring the olfactory system

2011 ◽  
Vol 2 (4) ◽  
Author(s):  
Albert Blanchart ◽  
Laura López-Mascaraque
Keyword(s):  
Olfactory Bulb ◽  
Olfactory System ◽  
Neural Circuit ◽  
Critical Role ◽  
Precise Location ◽  
Reliable Transmission ◽  
Molecular Events ◽  
Perfect Model ◽  
Molecular Signals ◽  
The Brain

AbstractThe olfactory system represents a perfect model to study the interactions between the central and peripheral nervous systems in order to establish a neural circuit during early embryonic development. In addition, another important feature of this system is the capability to integrate new cells generated in two neurogenic zones: the olfactory epithelium in the periphery and the wall of the lateral ventricles in the CNS, both during development and adulthood. In all these processes the combination and sequence of specific molecular signals plays a critical role in the wiring of the olfactory axons, as well as the precise location of the incoming cell populations to the olfactory bulb. The purpose of this review is to summarize recent insights into the cellular and molecular events that dictate cell settling position and axonal trajectories from their origin in the olfactory placode to the formation of synapses in the olfactory bulb to ensure rapid and reliable transmission of olfactory information from the nose to the brain.

Chemical Factors Determine Olfactory System Beta Oscillations in Waking Rats

2007 ◽  
Vol 98 (1) ◽  
pp. 394-404 ◽  
Author(s):  
Catherine A. Lowry ◽  
Leslie M. Kay
Keyword(s):  
Olfactory Bulb ◽  
Vapor Pressure ◽  
Vapor Phase ◽  
Local Field ◽  
Olfactory System ◽  
Piriform Cortex ◽  
Field Potential ◽  
Gamma Oscillations ◽  
Beta Oscillations ◽  
Phase Concentration

Recent studies have pointed to olfactory system beta oscillations of the local field potential (15–30 Hz) and their roles both in learning and as specific responses to predator odors. To describe odorant physical properties, resultant behavioral responses and changes in the central olfactory system that may induce these oscillations without associative learning, we tested rats with 26 monomolecular odorants spanning 6 log units of theoretical vapor pressure (estimate of relative vapor phase concentration) and 10 different odor mixtures. We found odorant vapor phase concentration to be inversely correlated with investigation time on the first presentation, after which investigation times were brief and not different across odorants. Analysis of local field potentials from the olfactory bulb and anterior piriform cortex shows that beta oscillations in waking rats occur specifically in response to the class of volatile organic compounds with vapor pressures of 1–120 mmHg. Beta oscillations develop over the first three to four presentations and are weakly present for some odorants in anesthetized rats. Gamma oscillations show a smaller effect that is not restricted to the same range of odorants. Olfactory bulb theta oscillations were also examined as a measure of effective afferent input strength, and the power of these oscillations did not vary systematically with vapor pressure, suggesting that it is not olfactory bulb drive strength that determines the presence of beta oscillations. Theta band coherence analysis shows that coupling strength between the olfactory bulb and piriform cortex increases linearly with vapor phase concentration, which may facilitate beta oscillations above a threshold.

scholarly journals mTOR signaling in VIP neurons regulates circadian clock synchrony and olfaction

2018 ◽  
Vol 115 (14) ◽  
pp. E3296-E3304 ◽  
Author(s):  
Dong Liu ◽  
Adam Stowie ◽  
Nuria de Zavalia ◽  
Tanya Leise ◽  
Salil Saurav Pathak ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Critical Role ◽  
Piriform Cortex ◽  
Brain Regions ◽  
Mtor Signaling ◽  
Adult Brain ◽  
Olfactory Pathway ◽  
Knockout Mouse Model ◽  
Dividing Cells ◽  
Circadian Behavior

Mammalian/mechanistic target of rapamycin (mTOR) signaling controls cell growth, proliferation, and metabolism in dividing cells. Less is known regarding its function in postmitotic neurons in the adult brain. Here we created a conditional mTOR knockout mouse model to address this question. Using the Cre-LoxP system, the mTOR gene was specifically knocked out in cells expressing Vip (vasoactive intestinal peptide), which represent a major population of interneurons widely distributed in the neocortex, suprachiasmatic nucleus (SCN), olfactory bulb (OB), and other brain regions. Using a combination of biochemical, behavioral, and imaging approaches, we found that mice lacking mTOR in VIP neurons displayed erratic circadian behavior and weakened synchronization among cells in the SCN, the master circadian pacemaker in mammals. Furthermore, we have discovered a critical role for mTOR signaling in mediating olfaction. Odor stimulated mTOR activation in the OB, anterior olfactory nucleus, as well as piriform cortex. Odor-evoked c-Fos responses along the olfactory pathway were abolished in mice lacking mTOR in VIP neurons, which is consistent with reduced olfactory sensitivity in these animals. Together, these results demonstrate that mTOR is a key regulator of SCN circadian clock synchrony and olfaction.

scholarly journals Perturbation of in vivo neural activity following α-Synuclein seeding in the olfactory bulb

2020 ◽  
Author(s):  
Aishwarya S. Kulkarni ◽  
Maria del Mar Cortijo ◽  
Elizabeth R. Roberts ◽  
Tamara L. Suggs ◽  
Heather B. Stover ◽  
...  
Keyword(s):  
Olfactory Bulb ◽  
Neural Activity ◽  
Olfactory System ◽  
Piriform Cortex ◽  
Field Potential ◽  
Dopamine Neurons ◽  
Motor Deficits ◽  
Wild Type ◽  
Evoked Activity

AbstractBACKGROUNDParkinson’s disease (PD) neuropathology is characterized by intraneuronal protein aggregates composed of misfolded α-Synuclein (α-Syn), as well as degeneration of substantia nigra dopamine neurons. Deficits in olfactory perception and aggregation of α-Syn in the olfactory bulb (OB) are observed during early stages of PD, and have been associated with the PD prodrome, before onset of the classic motor deficits. α-Syn fibrils injected into the OB of mice cause progressive propagation of α-Syn pathology throughout the olfactory system and are coupled to olfactory perceptual deficits.OBJECTIVEWe hypothesized that accumulation of pathogenic α-Syn in the OB impairs neural activity in the olfactory system.METHODSTo address this, we monitored spontaneous and odor-evoked local field potential dynamics in awake wild type mice simultaneously in the OB and piriform cortex (PCX) one, two, and three months following injection of pathogenic preformed α-Syn fibrils in the OB.RESULTSWe detected α-Syn pathology in both the OB and PCX. We also observed that α-Syn fibril injections influenced odor-evoked activity in the OB. In particular, α-Syn fibril-injected mice displayed aberrantly high odor-evoked power in the beta spectral range. A similar change in activity was not detected in the PCX, despite high levels of α-Syn pathology.CONCLUSIONSTogether, this work provides evidence that synucleinopathy impacts in vivo neural activity in the olfactory system at the network-level.

scholarly journals A transformation from temporal to ensemble coding in a model of piriform cortex

2017 ◽  
Author(s):  
Merav Stern ◽  
Kevin A. Bolding ◽  
L.F. Abbott ◽  
Kevin M. Franks
Keyword(s):  
Olfactory Bulb ◽  
Olfactory System ◽  
Feedback Inhibition ◽  
Piriform Cortex ◽  
Odor Coding ◽  
System A ◽  
Coding Strategies ◽  
Concentration Changes ◽  
Recurrent Collateral ◽  
The Impact

ABSTRACTDifferent coding strategies are used to represent odor information at various stages of the mammalian olfactory system. A temporal latency code represents odor identity in olfactory bulb (OB), but this temporal information is discarded in piriform cortex (PCx) where odor identity is instead encoded through ensemble membership. We developed a spiking PCx network model to understand how this transformation is implemented. In the model, the impact of OB inputs activated earliest after inhalation is amplified within PCx by diffuse recurrent collateral excitation, which then recruits strong, sustained feedback inhibition that suppresses the impact of later-responding glomeruli. Simultaneous OB-PCx recordings indicate that indeed, over a single sniff, the earliest-active OB inputs are most effective at driving PCx activity. We model increasing odor concentrations by decreasing glomerulus onset latencies while preserving their activation sequences. This produces a multiplexed cortical odor code in which activated ensembles are robust to concentration changes while concentration information is encoded through population synchrony. Our model demonstrates how PCx circuitry can implement multiplexed ensemble-identity/temporal-concentration odor coding.

scholarly journals Perturbation of in vivo Neural Activity Following α-Synuclein Seeding in the Olfactory Bulb

2020 ◽  
Vol 10 (4) ◽  
pp. 1411-1427
Author(s):  
Aishwarya S. Kulkarni ◽  
Maria del Mar Cortijo ◽  
Elizabeth R. Roberts ◽  
Tamara L. Suggs ◽  
Heather B. Stover ◽  
...  
Keyword(s):  
Olfactory Bulb ◽  
Neural Activity ◽  
Olfactory System ◽  
Piriform Cortex ◽  
Field Potential ◽  
Dopamine Neurons ◽  
Motor Deficits ◽  
Wild Type ◽  
Evoked Activity

Background: Parkinson’s disease (PD) neuropathology is characterized by intraneuronal protein aggregates composed of misfolded α-Synuclein (α-Syn), as well as degeneration of substantia nigra dopamine neurons. Deficits in olfactory perception and aggregation of α-Syn in the olfactory bulb (OB) are observed during early stages of PD, and have been associated with the PD prodrome, before onset of the classic motor deficits. α-Syn fibrils injected into the OB of mice cause progressive propagation of α-Syn pathology throughout the olfactory system and are coupled to olfactory perceptual deficits. Objective: We hypothesized that accumulation of pathogenic α-Syn in the OB impairs neural activity in the olfactory system. Methods: To address this, we monitored spontaneous and odor-evoked local field potential dynamics in awake wild type mice simultaneously in the OB and piriform cortex (PCX) one, two, and three months following injection of pathogenic preformed α-Syn fibrils in the OB. Results: We detected α-Syn pathology in both the OB and PCX. We also observed that α-Syn fibril injections influenced odor-evoked activity in the OB. In particular, α-Syn fibril-injected mice displayed aberrantly high odor-evoked power in the beta spectral range. A similar change in activity was not detected in the PCX, despite high levels of α-Syn pathology. Conclusion: Together, this work provides evidence that synucleinopathy impacts in vivo neural activity in the olfactory system at the network-level.

scholarly journals Temporal Structure of Receptor Neuron Input to the Olfactory Bulb Imaged in Behaving Rats

2009 ◽  
Vol 101 (2) ◽  
pp. 1073-1088 ◽  
Author(s):  
Ryan M. Carey ◽  
Justus V. Verhagen ◽  
Daniel W. Wesson ◽  
Nicolás Pírez ◽  
Matt Wachowiak
Keyword(s):  
Olfactory Bulb ◽  
Nasal Cavity ◽  
Rise Time ◽  
Olfactory System ◽  
Sensory Input ◽  
Temporal Structure ◽  
Critical Role ◽  
Progressive Increase ◽  
Sorption Kinetics ◽  
Temporal Organization

The dynamics of sensory input to the nervous system play a critical role in shaping higher-level processing. In the olfactory system, the dynamics of input from olfactory receptor neurons (ORNs) are poorly characterized and depend on multiple factors, including respiration-driven airflow through the nasal cavity, odorant sorption kinetics, receptor–ligand interactions between odorant and receptor, and the electrophysiological properties of ORNs. Here, we provide a detailed characterization of the temporal organization of ORN input to the mammalian olfactory bulb (OB) during natural respiration, using calcium imaging to monitor ORN input to the OB in awake, head-fixed rats expressing odor-guided behaviors. We report several key findings. First, across a population of homotypic ORNs, each inhalation of odorant evokes a burst of action potentials having a rise time of about 80 ms and a duration of about 100 ms. This rise time indicates a relatively slow, progressive increase in ORN activation as odorant flows through the nasal cavity. Second, the dynamics of ORN input differ among glomeruli and for different odorants and concentrations, but remain reliable across successive inhalations. Third, inhalation alone (in the absence of odorant) evokes ORN input to a significant fraction of OB glomeruli. Finally, high-frequency sniffing of odorant strongly reduces the temporal coupling between ORN inputs and the respiratory cycle. These results suggest that the dynamics of sensory input to the olfactory system may play a role in coding odor information and that, in the awake animal, strategies for processing odor information may change as a function of sampling behavior.

scholarly journals A transformation from temporal to ensemble coding in a model of piriform cortex

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Merav Stern ◽  
Kevin A Bolding ◽  
LF Abbott ◽  
Kevin M Franks
Keyword(s):  
Olfactory Bulb ◽  
Olfactory System ◽  
Feedback Inhibition ◽  
Piriform Cortex ◽  
Odor Coding ◽  
System A ◽  
Coding Strategies ◽  
Concentration Changes ◽  
Recurrent Collateral ◽  
The Impact

Different coding strategies are used to represent odor information at various stages of the mammalian olfactory system. A temporal latency code represents odor identity in olfactory bulb (OB), but this temporal information is discarded in piriform cortex (PCx) where odor identity is instead encoded through ensemble membership. We developed a spiking PCx network model to understand how this transformation is implemented. In the model, the impact of OB inputs activated earliest after inhalation is amplified within PCx by diffuse recurrent collateral excitation, which then recruits strong, sustained feedback inhibition that suppresses the impact of later-responding glomeruli. We model increasing odor concentrations by decreasing glomerulus onset latencies while preserving their activation sequences. This produces a multiplexed cortical odor code in which activated ensembles are robust to concentration changes while concentration information is encoded through population synchrony. Our model demonstrates how PCx circuitry can implement multiplexed ensemble-identity/temporal-concentration odor coding.

scholarly journals 50 years of decoding olfaction

2018 ◽  
Vol 2 ◽  
pp. 239821281881749 ◽  
Author(s):  
Peter A Brennan
Keyword(s):  
Olfactory Bulb ◽  
Olfactory System ◽  
Piriform Cortex ◽  
Vomeronasal System ◽  
Main Olfactory Bulb ◽  
Late 20Th Century ◽  
Fundamental Insight ◽  
Main Olfactory System ◽  
G Protein Coupled

The identification, in the late 20th century, of unexpectedly large families of G-protein-coupled chemosensory receptors revolutionised our understanding of the olfactory system. The discovery that non-selective olfactory sensory neurons express a single olfactory receptor type and project to a specific glomerulus in the main olfactory bulb provided fundamental insight into the spatial pattern of odour representation in the main olfactory bulb. Studies using head-fixed awake mice and optogenetics have revealed the importance of the timing of glomerular input in relation to the sniff cycle and the role of piriform cortex in odour object recognition. What in the 1970s had appeared to be a relatively simple dichotomy between odour detection by the main olfactory system and pheromone detection by the vomeronasal system has been found to consist of multiple subsystems. These mediate innate responses to odours and pheromones and to substances as diverse as O2, volatile urinary constituents, peptides and proteins.

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