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 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 Recurrent cortical circuits implement concentration-invariant odor coding

Science ◽  
2018 ◽  
Vol 361 (6407) ◽  
pp. eaat6904 ◽  
Author(s):  
Kevin A. Bolding ◽  
Kevin M. Franks
Keyword(s):  
Olfactory Bulb ◽  
Concentration Dependence ◽  
Neural Circuit ◽  
Feedback Inhibition ◽  
Piriform Cortex ◽  
Cortical Activity ◽  
Cortical Circuits ◽  
Odor Coding ◽  
Recurrent Collateral ◽  
The Impact

Animals rely on olfaction to find food, attract mates, and avoid predators. To support these behaviors, they must be able to identify odors across different odorant concentrations. The neural circuit operations that implement this concentration invariance remain unclear. We found that despite concentration-dependence in the olfactory bulb (OB), representations of odor identity were preserved downstream, in the piriform cortex (PCx). The OB cells responding earliest after inhalation drove robust responses in sparse subsets of PCx neurons. Recurrent collateral connections broadcast their activation across the PCx, recruiting global feedback inhibition that rapidly truncated and suppressed cortical activity for the remainder of the sniff, discounting the impact of slower, concentration-dependent OB inputs. Eliminating recurrent collateral output amplified PCx odor responses rendered the cortex steeply concentration-dependent and abolished concentration-invariant identity decoding.

scholarly journals Recurrent cortical circuits implement concentration-invariant odor coding

2018 ◽  
Author(s):  
Kevin A. Bolding ◽  
Kevin M. Franks
Keyword(s):  
Olfactory Bulb ◽  
Concentration Dependence ◽  
Neural Circuit ◽  
Feedback Inhibition ◽  
Piriform Cortex ◽  
Cortical Activity ◽  
Cortical Circuits ◽  
Odor Coding ◽  
Recurrent Collateral ◽  
The Impact

Animals rely on olfaction to find food, attract mates and avoid predators. To support these behaviors, animals must reliably identify odors across different odorant concentrations. The neural circuit operations that implement this concentration invariance remain unclear. Here we demonstrate that, despite concentration-dependence in olfactory bulb (OB), representations of odor identity are preserved downstream, in piriform cortex (PCx). The OB cells responding earliest after inhalation drive robust responses in a sparse subset of PCx neurons. Recurrent collateral connections broadcast their activation across PCx, recruiting strong, global feedback inhibition that rapidly suppresses cortical activity for the remainder of the sniff, thereby discounting the impact of slower, concentration-dependent OB inputs. Eliminating recurrent collateral output dramatically amplifies PCx odor responses, renders cortex steeply concentration-dependent, and abolishes concentration-invariant identity decoding.

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 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 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 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.

scholarly journals Spontaneous activity in the piriform cortex extends the dynamic range of cortical odor coding

2017 ◽  
Vol 114 (9) ◽  
pp. 2407-2412 ◽  
Author(s):  
Malinda L. S. Tantirigama ◽  
Helena H.-Y. Huang ◽  
John M. Bekkers
Keyword(s):  
Olfactory Bulb ◽  
Spontaneous Activity ◽  
Dynamic Range ◽  
Piriform Cortex ◽  
Spontaneous Firing ◽  
Odor Coding ◽  
Layer 2 ◽  
Olfactory Stimuli ◽  
External Stimuli ◽  
Odor Representation

Neurons in the neocortex exhibit spontaneous spiking activity in the absence of external stimuli, but the origin and functions of this activity remain uncertain. Here, we show that spontaneous spiking is also prominent in a sensory paleocortex, the primary olfactory (piriform) cortex of mice. In the absence of applied odors, piriform neurons exhibit spontaneous firing at mean rates that vary systematically among neuronal classes. This activity requires the participation of NMDA receptors and is entirely driven by bottom-up spontaneous input from the olfactory bulb. Odor stimulation produces two types of spatially dispersed, odor-distinctive patterns of responses in piriform cortex layer 2 principal cells: Approximately 15% of cells are excited by odor, and another approximately 15% have their spontaneous activity suppressed. Our results show that, by allowing odor-evoked suppression as well as excitation, the responsiveness of piriform neurons is at least twofold less sparse than currently believed. Hence, by enabling bidirectional changes in spiking around an elevated baseline, spontaneous activity in the piriform cortex extends the dynamic range of odor representation and enriches the coding space for the representation of complex olfactory stimuli.

scholarly journals Coding of odor stimulus features among secondary olfactory structures

2015 ◽  
Vol 114 (1) ◽  
pp. 736-745 ◽  
Author(s):  
Christina Z. Xia ◽  
Stacey Adjei ◽  
Daniel W. Wesson
Keyword(s):  
Olfactory System ◽  
Piriform Cortex ◽  
Odor Stimulus ◽  
Odor Perception ◽  
Odor Coding ◽  
Network Function ◽  
Complex Functions ◽  
Odor Exposure ◽  
Stimulus Features ◽  
The Brain

Sensory systems must represent stimuli in manners dependent upon a wealth of factors, including stimulus intensity and duration. One way the brain might handle these complex functions is to assign the tasks throughout distributed nodes, each contributing to information processing. We sought to explore this important aspect of sensory network function in the mammalian olfactory system, wherein the intensity and duration of odor exposure are critical contributors to odor perception. This is a quintessential model for exploring processing schemes given the distribution of odor information by olfactory bulb mitral and tufted cells into several anatomically distinct secondary processing stages, including the piriform cortex (PCX) and olfactory tubercle (OT), whose unique contributions to odor coding are unresolved. We explored the coding of PCX and OT neuron responses to odor intensity and duration. We found that both structures similarly partake in representing descending intensities of odors by reduced recruitment and modulation of neurons. Additionally, while neurons in the OT adapt to odor exposure, they display reduced capacity to adapt to either repeated presentations of odor or a single prolonged odor presentation compared with neurons in the PCX. These results provide insights into manners whereby secondary olfactory structures may, at least in some cases, uniquely represent stimulus features.

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