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Frontiers in Neural Circuits 2020Olfaction plays an important role in the evaluation, motivation, and palatability of food. The chemical identity of odorants is coded by a spatial combination of... (Review)
Review
Olfaction plays an important role in the evaluation, motivation, and palatability of food. The chemical identity of odorants is coded by a spatial combination of activated glomeruli in the olfactory bulb, which is referred to as the odor map. However, the functional roles of the olfactory cortex, a collective region that receives axonal projections from the olfactory bulb, and higher olfactory centers in odor-guided eating behaviors are yet to be elucidated. The olfactory tubercle (OT) is a component of the ventral striatum and forms a node within the mesolimbic dopaminergic pathway. Recent studies have revealed the anatomical domain structures of the OT and their functions in distinct odor-guided motivated behaviors. Another component of the ventral striatum, the nucleus accumbens, is well known for its involvement in motivation and hedonic responses for foods, which raises the possibility of functional similarities between the OT and nucleus accumbens in eating. This review first summarizes recent findings on the domain- and neuronal subtype-specific roles of the OT in odor-guided motivated behaviors and then proposes a model for the regulation of eating behaviors by the OT.
Topics: Animals; Feeding Behavior; Humans; Motivation; Nucleus Accumbens; Odorants; Olfactory Tubercle
PubMed: 33262693
DOI: 10.3389/fncir.2020.577880 -
Frontiers in Neural Circuits 2024The olfactory tubercle (OT) is a unique part of the olfactory cortex of the mammal brain in that it is also a component of the ventral striatum. It is crucially involved... (Review)
Review
The olfactory tubercle (OT) is a unique part of the olfactory cortex of the mammal brain in that it is also a component of the ventral striatum. It is crucially involved in motivational behaviors, particularly in adaptive olfactory learning. This review introduces the basic properties of the OT, its synaptic connectivity with other brain areas, and the plasticity of the connectivity associated with learning behavior. The adaptive properties of olfactory behavior are discussed further based on the characteristics of OT neuronal circuits.
Topics: Animals; Neuronal Plasticity; Humans; Olfactory Tubercle; Learning
PubMed: 38841557
DOI: 10.3389/fncir.2024.1423505 -
Journal of Neurochemistry Feb 2020The ventral striatum is a collection of brain structures, including the nucleus accumbens, ventral pallidum and the olfactory tubercle (OT). While much attention has... (Review)
Review
The ventral striatum is a collection of brain structures, including the nucleus accumbens, ventral pallidum and the olfactory tubercle (OT). While much attention has been devoted to the nucleus accumbens, a comprehensive understanding of the ventral striatum and its contributions to neurological diseases requires an appreciation for the complex neurochemical makeup of the ventral striatum's other components. This review summarizes the rich neurochemical composition of the OT, including the neurotransmitters, neuromodulators and hormones present. We also address the receptors and transporters involved in each system as well as their putative functional roles. Finally, we end with briefly reviewing select literature regarding neurochemical changes in the OT in the context of neurological disorders, specifically neurodegenerative disorders. By overviewing the vast literature on the neurochemical composition of the OT, this review will serve to aid future research into the neurobiology of the ventral striatum.
Topics: Animals; Humans; Olfactory Tubercle; Ventral Striatum
PubMed: 31755104
DOI: 10.1111/jnc.14919 -
Frontiers in Neural Circuits 2024Olfactory dysfunctions decrease daily quality of life (QOL) in part by reducing the pleasure of eating. Olfaction plays an essential role in flavor sensation and... (Review)
Review
Olfactory dysfunctions decrease daily quality of life (QOL) in part by reducing the pleasure of eating. Olfaction plays an essential role in flavor sensation and palatability. The decreased QOL due to olfactory dysfunction is speculated to result from abnormal neural activities in the olfactory and limbic areas of the brain, as well as peripheral odorant receptor dysfunctions. However, the specific underlying neurobiological mechanisms remain unclear. As the olfactory tubercle (OT) is one of the brain's regions with high expression of endogenous opioids, we hypothesize that the mechanism underlying the decrease in QOL due to olfactory dysfunction involves the reduction of neural activity in the OT and subsequent endogenous opioid release in specialized subregions. In this review, we provide an overview and recent updates on the OT, the endogenous opioid system, and the pleasure systems in the brain and then discuss our hypothesis. To facilitate the effective treatment of olfactory dysfunctions and decreased QOL, elucidation of the neurobiological mechanisms underlying the pleasure of eating through flavor sensation is crucial.
Topics: Humans; Quality of Life; Animals; Smell; Opioid Peptides; Olfactory Tubercle; Olfaction Disorders
PubMed: 38872907
DOI: 10.3389/fncir.2024.1408189 -
Frontiers in Neuroanatomy 2017Understanding of the olfactory neural circuits has progressed beyond analysis of how odor information from the external environment is processed in the brain. While... (Review)
Review
Understanding of the olfactory neural circuits has progressed beyond analysis of how odor information from the external environment is processed in the brain. While spatially-organized sub-circuits were found to exist up to the olfactory bulb (OB), the arrangement in the olfactory cortex (OC), especially in its representative piriform cortex (PC), appears diffuse and dispersed. An emerging view is that the activity of OC neurons may not simply encode odor identity but rather encode plastic odor information such as odor value. Although many studies support this notion, odor value can be either positive or negative, and the existence of sub-circuits corresponding to individual value types is not well explored. To address this question, I introduce here two olfactory areas other than the PC, OB and olfactory tubercle (OT) whose analysis may facilitate understanding of functional sub-circuits related to different odor values. Peripheral and centrifugal inputs to the OB are considered to relate to odor identity and odor value, respectively and centrifugal inputs to the OB potentially represent different odor values during different behavioral periods. The OT has spatially-segregated functional domains related to distinct motivated and hedonic behaviors. Thus, the OT provides a good starting point from which functional sub-circuits across various olfactory regions can be traced. Further analysis across wide areas of the olfactory system will likely reveal the functional sub-circuits that link odor identity with distinct odor values and direct distinct odor-induced motivated and hedonic behaviors.
PubMed: 28443001
DOI: 10.3389/fnana.2017.00033 -
Chemical Senses Sep 2016Modern neuroscience often relies upon artistic renderings to illustrate key aspects of anatomy. These renderings can be in 2 or even 3 dimensions. Three-dimensional... (Review)
Review
Modern neuroscience often relies upon artistic renderings to illustrate key aspects of anatomy. These renderings can be in 2 or even 3 dimensions. Three-dimensional renderings are especially helpful in conceptualizing highly complex aspects of neuroanatomy which otherwise are not visually apparent in 2 dimensions or even intact biological samples themselves. Here, we provide 3 dimensional renderings of the gross- and cellular-anatomy of the rodent olfactory tubercle. Based upon standing literature and detailed investigations into rat brain specimens, we created biologically inspired illustrations of the olfactory tubercle in 3 dimensions as well as its connectivity with olfactory bulb projection neurons, the piriform cortex association fiber system, and ventral pallidum medium spiny neurons. Together, we intend for these illustrations to serve as a resource to the neuroscience community in conceptualizing and discussing this highly complex and interconnected brain system with established roles in sensory processing and motivated behaviors.
Topics: Animals; Olfactory Tubercle; Rats; Ventral Striatum
PubMed: 27340137
DOI: 10.1093/chemse/bjw069 -
Neuroscience and Biobehavioral Reviews Jan 2011Since its designation in 1896 as a putative olfactory structure, the olfactory tubercle has received little attention in terms of elucidating its role in the processing... (Review)
Review
Since its designation in 1896 as a putative olfactory structure, the olfactory tubercle has received little attention in terms of elucidating its role in the processing and perception of odors. Instead, research on the olfactory tubercle has mostly focused on its relationship with the reward system. Here we provide a comprehensive review of research on the olfactory tubercle-with an emphasis on the likely role of this region in olfactory processing and its contributions to perception. Further, we propose several testable hypotheses regarding the likely involvement of the olfactory tubercle in both basic (odor detection, discrimination, parallel processing of olfactory information) and higher-order (social odor processing, hedonics, multi-modal integration) functions. Together, the information within this review highlights an understudied yet potentially critical component in central odor processing.
Topics: Animals; Humans; Odorants; Olfactory Pathways; Perception; Sensation; Smell
PubMed: 20800615
DOI: 10.1016/j.neubiorev.2010.08.004 -
Current Opinion in Neurobiology Feb 2014Sensory information in the visual, auditory and somatosensory systems is organized topographically, with key sensory features ordered in space across neural sheets.... (Review)
Review
Sensory information in the visual, auditory and somatosensory systems is organized topographically, with key sensory features ordered in space across neural sheets. Despite the existence of a spatially stereotyped map of odor identity within the olfactory bulb, it is unclear whether the higher olfactory cortex uses topography to organize information about smells. Here, we review recent work on the anatomy, microcircuitry and neuromodulation of two higher-order olfactory areas: the piriform cortex and the olfactory tubercle. The piriform is an archicortical region with an extensive local associational network that constructs representations of odor identity. The olfactory tubercle is an extension of the ventral striatum that may use reward-based learning rules to encode odor valence. We argue that in contrast to brain circuits for other sensory modalities, both the piriform and the olfactory tubercle largely discard any topography present in the bulb and instead use distributive afferent connectivity, local learning rules and input from neuromodulatory centers to build behaviorally relevant representations of olfactory stimuli.
Topics: Animals; Brain Mapping; Humans; Models, Neurological; Olfactory Pathways; Olfactory Perception
PubMed: 24492088
DOI: 10.1016/j.conb.2013.09.010 -
Nature Communications Oct 2023The ventral striatum is a reward center implicated in the pathophysiology of depression. It contains islands of Calleja, clusters of dopamine D3 receptor-expressing...
The ventral striatum is a reward center implicated in the pathophysiology of depression. It contains islands of Calleja, clusters of dopamine D3 receptor-expressing granule cells, predominantly in the olfactory tubercle (OT). These OT D3 neurons regulate self-grooming, a repetitive behavior manifested in affective disorders. Here we show that chronic restraint stress (CRS) induces robust depression-like behaviors in mice and decreases excitability of OT D3 neurons. Ablation or inhibition of these neurons leads to depression-like behaviors, whereas their activation ameliorates CRS-induced depression-like behaviors. Moreover, activation of OT D3 neurons has a rewarding effect, which diminishes when grooming is blocked. Finally, we propose a model that explains how OT D3 neurons may influence dopamine release via synaptic connections with OT spiny projection neurons (SPNs) that project to midbrain dopamine neurons. Our study reveals a crucial role of OT D3 neurons in bidirectionally mediating depression-like behaviors, suggesting a potential therapeutic target.
Topics: Mice; Animals; Islands of Calleja; Depression; Ventral Striatum; Olfactory Tubercle; Dopaminergic Neurons
PubMed: 37898623
DOI: 10.1038/s41467-023-42662-z -
The Journal of Neuroscience : the... Sep 2020In the mid-19th century, a misconception was born, which understandably persists in the minds of many neuroscientists today. The eminent scientist Albert von Kölliker... (Review)
Review
In the mid-19th century, a misconception was born, which understandably persists in the minds of many neuroscientists today. The eminent scientist Albert von Kölliker named a tubular-shaped piece of tissue found in the brains of all mammals studied to date, the tuberculum olfactorium - or what is commonly known as the olfactory tubercle (OT). In doing this, Kölliker ascribed "olfactory" functions and an "olfactory" purpose to the OT. The OT has since been classified as one of several olfactory cortices. However, further investigations of OT functions, especially over the last decade, have provided evidence for roles of the OT beyond olfaction, including in learning, motivated behaviors, and even seeking of psychoactive drugs. Indeed, research to date suggests caution in assigning the OT with a purely olfactory role. Here, I build on previous research to synthesize a model wherein the OT, which may be more appropriately termed the "tubular striatum" (TuS), is a neural system in which sensory information derived from an organism's experiences is integrated with information about its motivational states to guide affective and behavioral responses.
Topics: Animals; Corpus Striatum; Humans; Olfactory Perception
PubMed: 32968026
DOI: 10.1523/JNEUROSCI.1109-20.2020