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Communications Biology Sep 2022The olfactory nerve map describes the topographical neural connections between the olfactory epithelium in the nasal cavity and the olfactory bulb. Previous studies have...
The olfactory nerve map describes the topographical neural connections between the olfactory epithelium in the nasal cavity and the olfactory bulb. Previous studies have constructed the olfactory nerve maps of rodents using histological analyses or transgenic animal models to investigate olfactory nerve pathways. However, the human olfactory nerve map remains unknown. Here, we demonstrate that high-field magnetic resonance imaging and diffusion tensor tractography can be used to visualize olfactory sensory neurons while maintaining their three-dimensional structures. This technique allowed us to evaluate the olfactory sensory neuron projections from the nasal cavities to the olfactory bulbs and visualize the olfactory nerve maps of humans, marmosets and mice. The olfactory nerve maps revealed that the dorsal-ventral and medial-lateral axes were preserved between the olfactory epithelium and olfactory bulb in all three species. Further development of this technique might allow it to be used clinically to facilitate the diagnosis of olfactory dysfunction.
Topics: Animals; Humans; Magnetic Resonance Imaging; Mice; Olfactory Bulb; Olfactory Mucosa; Olfactory Nerve; Olfactory Pathways
PubMed: 36068329
DOI: 10.1038/s42003-022-03794-y -
European Archives of... Jan 2019To evaluate the olfactory function and the olfactory bulb (OB) volume changes in Wilson's Disease (WD) patients.
PURPOSE
To evaluate the olfactory function and the olfactory bulb (OB) volume changes in Wilson's Disease (WD) patients.
METHODS
A prospective, controlled, single-blinded study was planned. 12 patients with WD (Group 1) and 12 healthy subjects (Group 2) were included in the study. Connecticut Chemosensory Clinical Research Center (CCCRC) test was applied to evaluate olfactory functions. OB volumes were measured with a 1.5 T General Electric Signa Excite MRI scanner.
RESULTS
There was a significant difference between the CCCRC scores of the two groups (p < 0.05). The difference of the OB volumes of the two groups was insignificant (p > 0.05).
CONCLUSIONS
WD patients are likely to experience olfactory dysfunction, so its assessment may be a useful tool to the follow-up care of these patients, although further studies are needed to evaluate correlations in WD evolution.
Topics: Adult; Female; Healthy Volunteers; Hepatolenticular Degeneration; Humans; Magnetic Resonance Imaging; Male; Olfactory Bulb; Prospective Studies; Single-Blind Method; Smell
PubMed: 30467777
DOI: 10.1007/s00405-018-5216-9 -
Neural Plasticity 2015The olfactory system provides a great opportunity to explore the mechanisms that underlie the formation and function of neural circuits because of the simplicity of its... (Review)
Review
The olfactory system provides a great opportunity to explore the mechanisms that underlie the formation and function of neural circuits because of the simplicity of its structure. Olfactory sensory neurons (OSNs) located in the peripheral olfactory epithelium (OE) take part in the initial formation and function of glomeruli in the olfactory bulb (OB) inside the central nervous system. Glomeruli are key in the process of transduction of olfactory information, as they constitute a map in the OB that sorts the different types of odorant inputs. This odorant categorization allows proper olfactory perception, and it is achieved through the anatomical organization and function of the different glomerular circuits. Once formed, glomeruli keep the capacity to undergo diverse plasticity processes, which is unique among the different neural circuits of the central nervous system. In this context, through the expression and function of the odorant receptors (ORs), OSNs perform two of the most important roles in the olfactory system: transducing odorant information to the nervous system and initiating the development of the glomerular map to organize olfactory information. This review addresses essential information that has emerged in recent years about the molecular basis of these processes.
Topics: Animals; Humans; Neuronal Plasticity; Olfactory Bulb; Olfactory Receptor Neurons; Receptors, Odorant; Smell
PubMed: 25688305
DOI: 10.1155/2015/975367 -
Folia Morphologica 2021The aim of this study was to determine the normal reference values for olfactory sulcus depth, olfactory tract length and olfactory bulb volume in the paediatric...
BACKGROUND
The aim of this study was to determine the normal reference values for olfactory sulcus depth, olfactory tract length and olfactory bulb volume in the paediatric population with routine magnetic resonance imaging (MRI) and determine the relationship, if any, between these values and patient sex and age.
MATERIALS AND METHODS
Ninety patients with a median age of 8 years (age range: 3-17 years), consisting of 45 males and 45 females with normal brain MRI scans were evaluated. The patients were divided into three subgroups based on age range, with n = 30 per subgroup; group 1: young children (3-6 years), group 2: children (7-11 years) and group 3: adolescents (12-17 years). In the cranial MRI examination of all groups, the right, left and total olfactory bulb volume values were measured in mm3, the right and left olfactory tract length values and the right and left olfactory sulcus depth values were calculated manually in mm. Demographic data including sex and age were recorded.
RESULTS
There was no significant difference between the age groups in terms of sex. Right-left olfactory sulcus depth; right-left olfactory tract length and right-left total olfactory bulb volume values increased significantly when they are compared in terms of age groups (p < 0.0001, = 0.028; < 0.0001, < 0.0001; < 0.0001, < 0.0001; < 0.0001, respectively). There was no significant difference between right and left olfactory tract length and olfactory bulb volumes in all groups (p = 0.792 and p = 0.478), but the right olfactory sulcus depth was significantly larger than the left (p = 0.003).
CONCLUSIONS
Especially as the age progresses, olfactory tract length and olfactory bulb volume dimensions of olfactory nerve and olfactory sulcus depth should be checked during diagnosis of respective illnesses in paediatric population.
Topics: Adolescent; Adult; Child; Child, Preschool; Female; Humans; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Male; Olfaction Disorders; Olfactory Bulb; Prefrontal Cortex
PubMed: 33084007
DOI: 10.5603/FM.a2020.0125 -
Journal of Neurophysiology Oct 2017Synaptic inhibition critically influences sensory processing throughout the mammalian brain, including the main olfactory bulb (MOB), the first station of sensory... (Review)
Review
Synaptic inhibition critically influences sensory processing throughout the mammalian brain, including the main olfactory bulb (MOB), the first station of sensory processing in the olfactory system. Decades of research across numerous laboratories have established a central role for granule cells (GCs), the most abundant GABAergic interneuron type in the MOB, in the precise regulation of principal mitral and tufted cell (M/TC) firing rates and synchrony through lateral and recurrent inhibitory mechanisms. In addition to GCs, however, the MOB contains a vast diversity of other GABAergic interneuron types, and recent findings suggest that, while fewer in number, these oft-ignored interneurons are just as important as GCs in shaping odor-evoked M/TC activity. Here I challenge the prevailing centrality of GCs. In this review, I first outline the specific properties of each GABAergic interneuron type in the rodent MOB, with particular emphasis placed on direct interneuron recordings and cell type-selective manipulations. On the basis of these properties, I then critically reevaluate the contribution of GCs vs. other interneuron types to the regulation of odor-evoked M/TC firing rates and synchrony via lateral, recurrent, and other inhibitory mechanisms. This analysis yields a novel model in which multiple interneuron types with distinct abundances, connectivity patterns, and physiologies complement one another to regulate M/TC activity and sensory processing.
Topics: Animals; GABAergic Neurons; Interneurons; Mammals; Olfactory Bulb
PubMed: 28724776
DOI: 10.1152/jn.00109.2017 -
Brain Structure & Function Sep 2014Parkinson's disease (PD) is a neurodegenerative disease characterized by bradykinesia, rigidity, resting tremor, and postural instability. Neuropathologically,... (Review)
Review
Parkinson's disease (PD) is a neurodegenerative disease characterized by bradykinesia, rigidity, resting tremor, and postural instability. Neuropathologically, intracellular aggregates of α-synuclein in Lewy bodies and Lewy neurites appear in particular brain areas according to a sequence of stages. Clinical diagnosis is usually established when motor symptoms are evident (corresponding to Braak stage III or later), years or even decades after onset of the disease. Research at early stages is therefore essential to understand the etiology of PD and improve treatment. Although classically considered as a motor disease, non-motor symptoms have recently gained interest. Olfactory deficits are among the earliest non-motor features of PD. Interestingly, α-synuclein deposits are present in the olfactory bulb and anterior olfactory nucleus at Braak stage I. Several lines of evidence have led to proposals that PD pathology spreads by a prion-like mechanism via the olfactory and vagal systems to the substantia nigra. In this context, current data on the temporal appearance of α-synuclein aggregates in the olfactory system of both humans and transgenic mice are of particular relevance. In addition to the proposed retrograde nigral involvement via brainstem nuclei, olfactory pathways could potentially reach the substantia nigra, and the possibility of centrifugal progression warrants investigation. This review analyzes the involvement of α-synuclein in different elements of the olfactory system, in both humans and transgenic models, from the hodological perspective of possible anterograde and/or retrograde progression of this proteinopathy within the olfactory system and beyond-to the substantia nigra and the remainder of the central and peripheral nervous systems.
Topics: Animals; Humans; Olfactory Bulb; Olfactory Pathways; Parkinson Disease; alpha-Synuclein
PubMed: 24135772
DOI: 10.1007/s00429-013-0651-2 -
Folia Morphologica 2022This study aimed to reveal the change in olfactory bulbus volume (OBV) and olfactory sulcus depth (OSD) in healthy Turkish paediatric individuals between 1 month and 18...
BACKGROUND
This study aimed to reveal the change in olfactory bulbus volume (OBV) and olfactory sulcus depth (OSD) in healthy Turkish paediatric individuals between 1 month and 18 years of age with 3 Tesla magnetic resonance imaging (MRI), taking into account different age groups and gender factors.
MATERIALS AND METHODS
In this retrospective study, 190 paediatric individuals who underwent cranial MRI were evaluated. Healthy paediatric cases were divided into four groups as infantile period (first 24 months when cerebral myelinisation was completed), early childhood (2-6 years), childhood (6-12 years) and adolescence (12-18 years). OBV and OSD measurements were performed on coronal T2-weighted brain MRI by 3 Tesla magnetic resonance scan. The mean, right and left OBVs and OSDs were used for evaluation.
RESULTS
The mean age was 9.9 ± 7.5 months for the infantile period, 4.5 ± 1.3 years for early childhood, 9.3 ± 1.7 years for childhood and 15.2 ± 1.7 years for adolescence. Mean, right and left OBV was found to be slightly larger in male children than in female children (p = 0.015, p = 0.033 and p = 0.010, respectively). There was no statistical difference between the genders for mean, right and left OSD (p = 0.559, p = 0.536 and p = 0.598, respectively). Among the age groups, the values of the 3rd and 4th groups in terms of mean, right and left OBV were higher than in the other two groups (p < 0.001). In terms of OSD, mean, right and left values were higher in group 2, 3 and 4 than in group 1 (p < 0.001).
CONCLUSIONS
These data differ by paediatric age group and gender for the development of OBV and OSD. Normal values for the paediatric age group and gender should be calculated to detect olfactory dysfunction.
Topics: Adolescent; Child; Child, Preschool; Female; Humans; Infant; Magnetic Resonance Imaging; Male; Olfaction Disorders; Olfactory Bulb; Prefrontal Cortex; Retrospective Studies
PubMed: 33749801
DOI: 10.5603/FM.a2021.0022 -
The International Journal of... Sep 2017Evidence for olfactory dysfunction in schizophrenia has been firmly established. However, in the typical understanding of schizophrenia, olfaction is not recognized to...
BACKGROUND
Evidence for olfactory dysfunction in schizophrenia has been firmly established. However, in the typical understanding of schizophrenia, olfaction is not recognized to contribute to or interact with the illness. Despite the solid presence of olfactory dysfunction in schizophrenia, its relation to the rest of the illness remains largely unclear. Here, we aimed to examine functional connectivity of the olfactory bulb, olfactory tract, and piriform cortices and isolate the network that would account for the altered olfaction in schizophrenia.
METHODS
We examined the functional connectivity of these specific olfactory regions in order to isolate other brain regions associated with olfactory processing in schizophrenia. Using the resting state functional MRI data from the Center for Biomedical Research Excellence in Brain Function and Mental Illness, we compared 84 patients of schizophrenia and 90 individuals without schizophrenia.
RESULTS
The schizophrenia group showed disconnectivity between the anterior piriform cortex and the nucleus accumbens, between the posterior piriform cortex and the middle frontal gyrus, and between the olfactory tract and the visual cortices.
CONCLUSIONS
The current results suggest functional disconnectivity of olfactory regions in schizophrenia, which may account for olfactory dysfunction and disrupted integration with other sensory modalities in schizophrenia.
Topics: Adult; Brain Mapping; Case-Control Studies; Female; Frontal Lobe; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Male; Middle Aged; Olfaction Disorders; Olfactory Bulb; Olfactory Pathways; Oxygen; Rest; Schizophrenia; Young Adult
PubMed: 28582529
DOI: 10.1093/ijnp/pyx045 -
Cell and Tissue Research Jan 2021Evolutionarily, olfaction is one of the oldest senses and pivotal for an individual's health and survival. The olfactory bulb (OB), as the first olfactory relay station... (Review)
Review
Evolutionarily, olfaction is one of the oldest senses and pivotal for an individual's health and survival. The olfactory bulb (OB), as the first olfactory relay station in the brain, is known to heavily process sensory information. To adapt to an animal's needs, OB activity can be influenced by many factors either from within (intrinsic neuromodulation) or outside (extrinsic neuromodulation) the OB which include neurotransmitters, neuromodulators, hormones, and neuropeptides. Extrinsic sources seem to be of special importance as the OB receives massive efferent input from numerous brain centers even outweighing the sensory input from the nose. Here, we review neuromodulatory processes in the rodent OB from such extrinsic sources. We will discuss extrinsic neuromodulation according to points of origin, receptors involved, affected circuits, and changes in behavior. In the end, we give a brief outlook on potential future directions in research on neuromodulation in the OB.
Topics: Animals; Olfactory Bulb; Rodentia
PubMed: 33355709
DOI: 10.1007/s00441-020-03365-9 -
Acta Physiologica (Oxford, England) Oct 2019Leptin is an important peptide hormone that regulates food intake and plays a crucial role in modulating olfactory function. Although a few previous studies have...
AIM
Leptin is an important peptide hormone that regulates food intake and plays a crucial role in modulating olfactory function. Although a few previous studies have investigated the effect of leptin on odor perception and discrimination in rodents, research on the neural basis underlying the behavioral changes is lacking. Here we study how leptin affects behavioral performance during a go/no-go task and how it modulates neural activity of mitral/tufted cells in the olfactory bulb, which plays an important role in odor information processing and representation.
METHODS
A go/no-go odor discrimination task was used in the behavioral test. For in vivo studies, single unit recordings, local field potential recordings and fiber photometry recordings were used. For in vitro studies, we performed patch clamp recordings in the slice of the olfactory bulb.
RESULTS
Behaviorally, leptin affects performance and reaction time in a difficult odor-discrimination task. Leptin decreases the spontaneous firing of single mitral/tufted cells, decreases the odor-evoked beta and high gamma local field potential response, and has bidirectional effects on the odor-evoked responses of single mitral/tufted cells. Leptin also inhibits the population calcium activity in genetically identified mitral/tufted cells and granule cells. Furthermore, in vitro slice recordings reveal that leptin inhibits mitral cell activity through direct modulation of the voltage-sensitive potassium channel.
CONCLUSIONS
The behavioral reduction in odor discrimination observed after leptin administration is likely due to decreased neural activity in mitral/tufted cells, caused by modulation of potassium channels in these cells.
Topics: Action Potentials; Animals; Behavior, Animal; Electrophysiological Phenomena; Ketones; Leptin; Male; Mice; Odorants; Olfactory Bulb; Olfactory Perception; Patch-Clamp Techniques; Pentanols; Smell
PubMed: 31144469
DOI: 10.1111/apha.13319