Piriform Cortex and Olfactory Tubercle

Irritation and negative valence are closely associated in perception. However, these perceptual aspects can be dissociated in olfaction where irritation can accompany both pleasant and unpleasant odorants. Whereas the sensation of odor reflects transduction at olfactory receptors, irritation reflects concurrent transduction of the odorant at trigeminal receptors. Thus a stimulus can be either a pure olfactant activating the olfactory receptors only or a bimodal odorant activating both types of receptors. Using event-related functional magnetic resonance imaging and a 2 × 2 experimental design contrasting odorant valence (pleasant/unpleasant) and odorant type (pure olfactant/bimodal) we found activity in piriform cortex to be associated with valence, and not type, of odors. In contrast, activity in the olfactory tubercle was associated with type, and not valence, of odors. Importantly, this was found when perceived intensity was held equal across odorants. These findings suggest that dissociable neural substrates subserve the encoding of irritation and valence in olfaction.

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The Neurotransmitter Receptor Architecture of the Mouse Olfactory System

Frontiers in Neuroanatomy ◽

10.3389/fnana.2021.632549 ◽

2021 ◽

Vol 15 ◽

Author(s):

Kimberley Lothmann ◽

Katrin Amunts ◽

Christina Herold

Keyword(s):

Olfactory System ◽

Piriform Cortex ◽

Hierarchical Cluster ◽

Distribution Patterns ◽

Olfactory Cortex ◽

Cluster Solution ◽

Olfactory Tubercle ◽

Neurotransmitter Receptor ◽

Heterogeneous Expression

The uptake, transmission and processing of sensory olfactory information is modulated by inhibitory and excitatory receptors in the olfactory system. Previous studies have focused on the function of individual receptors in distinct brain areas, but the receptor architecture of the whole system remains unclear. Here, we analyzed the receptor profiles of the whole olfactory system of adult male mice. We examined the distribution patterns of glutamatergic (AMPA, kainate, mGlu2/3, and NMDA), GABAergic (GABAA, GABAA(BZ), and GABAB), dopaminergic (D1/5) and noradrenergic (α1 and α2) neurotransmitter receptors by quantitative in vitro receptor autoradiography combined with an analysis of the cyto- and myelo-architecture. We observed that each subarea of the olfactory system is characterized by individual densities of distinct neurotransmitter receptor types, leading to a region- and layer-specific receptor profile. Thereby, the investigated receptors in the respective areas and strata showed a heterogeneous expression. Generally, we detected high densities of mGlu2/3Rs, GABAA(BZ)Rs and GABABRs. Noradrenergic receptors revealed a highly heterogenic distribution, while the dopaminergic receptor D1/5 displayed low concentrations, except in the olfactory tubercle and the dorsal endopiriform nucleus. The similarities and dissimilarities of the area-specific multireceptor profiles were analyzed by a hierarchical cluster analysis. A three-cluster solution was found that divided the areas into the (1) olfactory relay stations (main and accessory olfactory bulb), (2) the olfactory cortex (anterior olfactory cortex, dorsal peduncular cortex, taenia tecta, piriform cortex, endopiriform nucleus, entorhinal cortex, orbitofrontal cortex) and the (3) olfactory tubercle, constituting its own cluster. The multimodal receptor-architectonic analysis of each component of the olfactory system provides new insights into its neurochemical organization and future possibilities for pharmaceutic targeting.

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Diversity of Neural Signals Mediated by Multiple, Burst-Firing Mechanisms in Rat Olfactory Tubercle Neurons

Journal of Neurophysiology ◽

10.1152/jn.00807.2007 ◽

2007 ◽

Vol 98 (5) ◽

pp. 2716-2728 ◽

Cited By ~ 11

Author(s):

Elizabeth Chiang ◽

Ben W. Strowbridge

Keyword(s):

Olfactory Bulb ◽

Piriform Cortex ◽

Calcium Currents ◽

Olfactory Tubercle ◽

Cellular Mechanisms ◽

Neural Signals ◽

Olfactory Information ◽

Whole Cell Patch Clamp ◽

Cell Layers ◽

Transient Events

Olfactory information is processed by a diverse group of interconnected forebrain regions. Most efforts to define the cellular mechanisms involved in processing olfactory information have been focused on understanding the function of the olfactory bulb, the primary second-order olfactory region, and its principal target, the piriform cortex. However, the olfactory bulb also projects to other targets, including the rarely studied olfactory tubercle, a ventral brain region recently implicated in regulating cocaine-related reward behavior. We used whole cell patch-clamp recordings from rat tubercle slices to define the intrinsic properties of neurons in the dense and multiform cell layers. We find three common firing modes of tubercle neurons: regular-spiking, intermittent-discharging, and bursting. Regular-spiking neurons are typically spiny-dense-cell-layer cells with pyramidal-shaped, dendritic arborizations. Intermittently discharging and bursting neurons comprise the majority of the deeper multiform layer and share a common morphology: multipolar, sparsely spiny cells. Rather than generating all-or-none stereotyped discharges, as observed in many brain areas, bursting cells in the tubercle generate depolarizing plateau potentials that trigger graded but time-limited discharges. We find two distinct subclasses of bursting cells that respond similarly to step stimuli but differ in the role transmembrane Ca currents play in their intrinsic behavior. Calcium currents amplify depolarizing inputs and enhance excitability in regenerative bursting cells, whereas the primary action of Ca in nonregenerative bursting tubercle neurons appears to be to decrease excitability by triggering Ca-activated K currents. Nonregenerative bursting cells exhibit a prolonged refractory period after even short discharges suggesting that they may function to detect transient events.

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Sharp wave-associated synchronized inputs from the piriform cortex activate olfactory tubercle neurons during slow-wave sleep

Journal of Neurophysiology ◽

10.1152/jn.00535.2013 ◽

2014 ◽

Vol 111 (1) ◽

pp. 72-81 ◽

Cited By ~ 14

Author(s):

Kimiya Narikiyo ◽

Hiroyuki Manabe ◽

Kensaku Mori

Keyword(s):

Slow Wave ◽

Olfactory System ◽

Slow Wave Sleep ◽

Piriform Cortex ◽

Current Source ◽

Olfactory Tubercle ◽

Neuronal Circuitry ◽

Anterior Piriform Cortex ◽

Sharp Waves ◽

Density Analysis

During slow-wave sleep, anterior piriform cortex neurons show highly synchronized discharges that accompany olfactory cortex sharp waves (OC-SPWs). The OC-SPW-related synchronized activity of anterior piriform cortex neurons travel down to the olfactory bulb and is thought to be involved in the reorganization of bulbar neuronal circuitry. However, influences of the OC-SPW-related activity on other regions of the central olfactory system are still unknown. Olfactory tubercle is an area of OC and part of ventral striatum that plays a key role in reward-directed motivational behaviors. In this study, we show that in freely behaving rats, olfactory tubercle receives OC-SPW-associated synchronized inputs during slow-wave sleep. Local field potentials in the olfactory tubercle showed SPW-like activities that were in synchrony with OC-SPWs. Single-unit recordings showed that a subpopulation of olfactory tubercle neurons discharged in synchrony with OC-SPWs. Furthermore, correlation analysis of spike activity of anterior piriform cortex and olfactory tubercle neurons revealed that the discharges of anterior piriform cortex neurons tended to precede those of olfactory tubercle neurons. Current source density analysis in urethane-anesthetized rats indicated that the current sink of the OC-SPW-associated input was located in layer III of the olfactory tubercle. These results indicate that OC-SPW-associated synchronized discharges of piriform cortex neurons travel to the deep layer of the olfactory tubercle and drive discharges of olfactory tubercle neurons. The entrainment of olfactory tubercle neurons in the OC-SPWs suggests that OC-SPWs coordinate reorganization of neuronal circuitry across wide areas of the central olfactory system including olfactory tubercle during slow-wave sleep.

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Functional Assessment of Intrahypothalamic Implants of Immortalized Gonadotropin-Releasing Hormone-Secreting Cells in Female Hypogonadal Mice

Cell Transplantation ◽

10.1177/096368979300200309 ◽

1993 ◽

Vol 2 (3) ◽

pp. 251-257 ◽

Cited By ~ 8

Author(s):

Gregory M. Miller ◽

Ann-Judith Silverman ◽

James L. Roberts ◽

Ke Wen Dong ◽

Marie J. Gibson

Keyword(s):

Functional Assessment ◽

Piriform Cortex ◽

Gonadotropin Releasing Hormone ◽

Olfactory Tubercle ◽

Secreting Cell ◽

Pharmacological Agents ◽

Releasing Hormone ◽

Lh Release ◽

Lh Secretion ◽

Intravenous Catheters

The hypogonadal (HPG) mouse is a mutant that lacks a functional gonadotropin-releasing hormone (GnRH) gene. In this study, female HPG mice received bilateral intrahypothalamic implants of an immortalized GnRH-secreting cell line (GT1-7). Nine mice were tested 42-65 days after implantation to determine whether these cells could support spontaneous and/or N-methyl-D, L,-aspartic acid (NMDA)-stimulated luteinizing hormone (LH) secretion. When sampled via intravenous catheters, four mice had measurable LH secretion. Three of these mice responded to NMDA challenges with significant increases in circulating LH. GnRH immunocytochemistry revealed that GT1-7 cells were present in these four mice and three others in which LH values were not detectable. There were about 1200 GnRH cells dispersed within the piriform cortex and olfactory tubercle, and no tumor found in one of the HPG mice that responded to NMDA, whereas the other NMDA responders had large bilateral hypothalamic tumors. The presence or absence of such tumors did not predict the capacity to respond to the NMDA challenge with alterations in LH secretion. This study provides the first evidence that intrahypothalamic GT1-7 cells can support LH release in the HPG mouse, and that this secretion can be modified by pharmacological agents.

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Glutamatergic Neurons in the Piriform Cortex Influence the Activity of D1- and D2-Type Receptor-Expressing Olfactory Tubercle Neurons

Journal of Neuroscience ◽

10.1523/jneurosci.1444-19.2019 ◽

2019 ◽

Vol 39 (48) ◽

pp. 9546-9559 ◽

Cited By ~ 3

Author(s):

Kate A. White ◽

Yun-Feng Zhang ◽

Zhijian Zhang ◽

Janardhan P. Bhattarai ◽

Andrew H. Moberly ◽

...

Keyword(s):

Piriform Cortex ◽

Olfactory Tubercle ◽

Glutamatergic Neurons ◽

Type Receptor

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Catecholamine innervation of the basal forebrain III. Olfactory bulb, anterior olfactory nuclei, olfactory tubercle and piriform cortex

The Journal of Comparative Neurology ◽

10.1002/cne.901800309 ◽

1978 ◽

Vol 180 (3) ◽

pp. 533-544 ◽

Cited By ~ 174

Author(s):

James H. Fallon ◽

Robert Y. Moore

Keyword(s):

Olfactory Bulb ◽

Basal Forebrain ◽

Piriform Cortex ◽

Olfactory Tubercle

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Rapid Sensorimotor Reinforcement in the Olfactory Striatum

10.1101/730697 ◽

2019 ◽

Author(s):

Daniel J. Millman ◽

Venkatesh N. Murthy

Keyword(s):

Sensory Input ◽

Piriform Cortex ◽

Explicit Representation ◽

Olfactory Tubercle ◽

Category Representation ◽

Stimulus Information ◽

Motor Action ◽

Stimulus Response ◽

Reward Prediction ◽

Support Decision Making

AbstractRodents can successfully learn multiple, novel stimulus-response associations after only a few repetitions when the contingencies predict reward. The circuits modified during such reinforcement learning to support decision making are not known, but the olfactory tubercle (OT) and posterior piriform cortex (pPC) are candidates for decoding reward category from olfactory sensory input and relaying this information to cognitive and motor areas. Here, we show that an explicit representation for reward category emerges in the OT within minutes of learning a novel odor-reward association, whereas the pPC lacks an explicit representation even after weeks of overtraining. The explicit reward category representation in OT is visible in the first sniff (50-100ms) of an odor on each trial, and precedes the motor action. Together, these results suggest that coding of stimulus information required for reward prediction does not occur within olfactory cortex, but rather in circuits involving the olfactory striatum.

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