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Diagnostic and Interventional Radiology... Mar 2023Olfactory dysfunction is a well-known complication in epilepsy. Studies have demonstrated that olfactory bulb volume (OBV), olfactory tract length (OTL), and olfactory...
PURPOSE
Olfactory dysfunction is a well-known complication in epilepsy. Studies have demonstrated that olfactory bulb volume (OBV), olfactory tract length (OTL), and olfactory sulcus depth (OSD) can be reliably evaluated using magnetic resonance imaging (MRI). In this study, we compared the OBV, OTL, and OSD values of children with epilepsy and those of healthy children (controls) of similar age. Our aim was to determine the presence of olfactory dysfunction in children with epilepsy and demonstrate the effects of the epilepsy type and treatment on olfactory function in these patients.
METHODS
Cranial MRI images of 36 patients with epilepsy and 108 controls (3-17 years) were evaluated. The patients with epilepsy were divided into groups according to the type of disease and treatment method. Subsequently, OBV and OSD were measured from the coronal section and OTL from the sagittal section. The OBV, OTL, and OSD values were compared between the epilepsy group, subgroups, and controls.
RESULTS
OBV was significantly reduced in the children with epilepsy compared with the control group ( < 0.001). No significant difference between the healthy children and those with epilepsy was determined in terms of OTL and OSD. Although OBV was moderately positively correlated with age in the control group (r = 0.561, < 0.001), it was poorly correlated with age in children with epilepsy (r = 0.393, = 0.018).
CONCLUSION
The results of our study indicate that OBV decreases in children with epilepsy, but epilepsy type and treatment method do not affect OBV, OTL, or OSD ( > 0.05).
Topics: Humans; Child; Magnetic Resonance Imaging; Epilepsy; Olfactory Bulb; Olfaction Disorders
PubMed: 36988051
DOI: 10.5152/dir.2022.21287 -
International Journal of Molecular... Feb 2023Centrifugal projections in the olfactory system are critical to both olfactory processing and behavior. The olfactory bulb (OB), the first relay station in odor...
Centrifugal projections in the olfactory system are critical to both olfactory processing and behavior. The olfactory bulb (OB), the first relay station in odor processing, receives a substantial number of centrifugal inputs from the central brain regions. However, the anatomical organization of these centrifugal connections has not been fully elucidated, especially for the excitatory projection neurons of the OB, the mitral/tufted cells (M/TCs). Using rabies virus-mediated retrograde monosynaptic tracing in Thy1-Cre mice, we identified that the three most prominent inputs of the M/TCs came from the anterior olfactory nucleus (AON), the piriform cortex (PC), and the basal forebrain (BF), similar to the granule cells (GCs), the most abundant population of inhibitory interneurons in the OB. However, M/TCs received proportionally less input from the primary olfactory cortical areas, including the AON and PC, but more input from the BF and contralateral brain regions than GCs. Unlike organizationally distinct inputs from the primary olfactory cortical areas to these two types of OB neurons, inputs from the BF were organized similarly. Furthermore, individual BF cholinergic neurons innervated multiple layers of the OB, forming synapses on both M/TCs and GCs. Taken together, our results indicate that the centrifugal projections to different types of OB neurons may provide complementary and coordinated strategies in olfactory processing and behavior.
Topics: Mice; Animals; Olfactory Bulb; Olfactory Pathways; Smell; Olfactory Cortex; Basal Forebrain
PubMed: 36902010
DOI: 10.3390/ijms24054579 -
ORL; Journal For Oto-rhino-laryngology... 2022While magnetic resonance imaging (MRI) is not included in the current guidelines for diagnosing olfactory disorders in the most recent position paper on olfactory...
INTRODUCTION
While magnetic resonance imaging (MRI) is not included in the current guidelines for diagnosing olfactory disorders in the most recent position paper on olfactory dysfunction, both 1.5T and 3T MRI are commonly used in the diagnostic workup of many patients with olfactory loss. Often, MRI is used to rule out intracranial tumours, but other useful information may be obtained from MRI scans in these patients. The potential of MRI in olfactory loss depends on sufficient knowledge of structural changes in different aetiologies of olfactory loss. We present common clinical MRI findings in olfactory loss and evaluate the usefulness of structural integrity scores in differentiating between aetiologies.
METHODS
In this study, we investigated if white matter hyperintensities (WMHs, measured by Fazekas score), global cortical atrophy (GCA), and medial temporal lobe atrophy (MTA) are more common in patients with idiopathic olfactory loss than in patients with acquired olfactory loss due to other aetiologies. Furthermore, we compared olfactory bulb (OB) configurations in different olfactory loss aetiologies.
RESULTS
In 88 patients with olfactory loss, WMHs, GCA, and MTA were not more significant findings on MRI in idiopathic olfactory loss (n = 51) compared with other causes of acquired olfactory loss (Fazekas score p = 0.2977; GCA score p = 0.6748; MTA score p = 0.7851). Bulb configurations differed in patients suffering from post-traumatic olfactory loss and may aid in identifying the underlying aetiology in patients where trauma is among the suspected causes of olfactory loss.
CONCLUSION
We recommend that structural MRI with an OB sequence is included in the diagnostic evaluation of olfactory loss with suspected congenital and post-traumatic aetiology and should be considered in idiopathic olfactory loss with suspected central aetiology (e.g., tumour).
Topics: Humans; Atrophy; Magnetic Resonance Imaging; Olfaction Disorders; Olfactory Bulb; White Matter
PubMed: 34879365
DOI: 10.1159/000520567 -
Proceedings of the National Academy of... Mar 2018Olfaction is an important sensory modality driving fundamental behaviors. During odor-dependent learning, a positive value is commonly assigned to an odorant, and...
Olfaction is an important sensory modality driving fundamental behaviors. During odor-dependent learning, a positive value is commonly assigned to an odorant, and multiple forms of plasticity are involved when such odor-reward associations are formed. In rodents, one of the mechanisms underlying plasticity in the olfactory bulb consists in recruiting new neurons daily throughout life. However, it is still unknown whether adult-born neurons might participate in encoding odor value. Here, we demonstrate that exposure to reward-associated odors specifically increases activity of adult-born neurons but not preexisting neurons. Remarkably, adult-born neuron activation during rewarded odor presentation heightens discrimination learning and enhances the ability to update the odor value during reversal association. Moreover, in some cases, activation of this interneuron population can trigger olfactory learning without sensory stimulation. Taken together, our results show a specific involvement of adult-born neurons in facilitating odor-reward association during adaptive learning.
Topics: Animals; Discrimination Learning; Female; Male; Models, Neurological; Odorants; Olfactory Bulb; Olfactory Receptor Neurons; Rats; Reward; Smell
PubMed: 29467284
DOI: 10.1073/pnas.1716400115 -
Balkan Medical Journal Jan 2019This report produces a bibliographic study of psychophysical tests proposed clinical assessments of retronasal olfaction.
BACKGROUND
This report produces a bibliographic study of psychophysical tests proposed clinical assessments of retronasal olfaction.
AIMS
We review how these tests can be utilized and discuss their methodological properties.
STUDY DESIGN
Systematic review.
METHODS
We undertook a systematic literature review investigating the retronasal olfaction test methods. PubMed, the free online MEDLINE database on biomedical sciences, was searched for the period from 1984 to 2015 using the following relevant key phrases: “retronasal olfaction”, “orthonasal olfaction”, “olfaction disorders”, and “olfaction test”. For each of the selected titles cited in this study, the full manuscript was read and analyzed by each of the three authors of this paper independently before collaborative discussion for summation and analytical reporting. Two reviewers independently read the abstracts and full texts and categorised them into one of three subgroups as follow, suitable, not-suitable, and unsure. Then they cross-checked the results, and a third reviewer decided assigned the group “unsure” to either the suitable group or the not-suitable group. Fifty eight studies revealed as suitable for review by two authors whereas 13 found not suitable for review. The total amount of 60 uncertain (unsure) or differently categorized articles were further examined by the third author which resulted in 41 approvals and 19 rejections. Hence 99 approved articles passed the next step. Exclusion criteria were reviews, case reports, animal studies, and the articles of which methodology was a lack of olfaction tests. By this way excluded 69 papers, and finally, 30 original human research articles were taken as the data.
RESULTS
The study found that the three most widely used and accepted retronasal olfaction test methods are the retronasal olfaction test, the candy smell test and odorant presentation containers. All of the three psychophysical retronasal olfaction tests were combined with orthonasal tests in clinical use to examine and understand the smell function of the patient completely. There were two limitations concerning testing: “the lack concentrations and doses of test materials” and “performing measurements within the supra-threshold zone”.
CONCLUSION
The appropriate test agents and optimal concentrations for the retronasal olfaction tests remain unclear and emerge as limitations of the retronasal olfaction test technique. The first step to overcoming these limitations will probably require identification of retronasal olfaction thresholds. Once these are determined, the concept of retronasal olfaction and its testing methods may be thoroughly reviewed.
Topics: Diagnostic Techniques, Neurological; Humans; Nasal Cavity; Olfaction Disorders; Olfactory Bulb; Smell
PubMed: 30264731
DOI: 10.4274/balkanmedj.2018.0052 -
International Journal of Occupational... Oct 2014Formaldehyde inhalation exposure, which can occur through occupational exposure, can lead to sensory irritation, neurotoxicity, mood disorders, and learning and memory...
BACKGROUND
Formaldehyde inhalation exposure, which can occur through occupational exposure, can lead to sensory irritation, neurotoxicity, mood disorders, and learning and memory impairment. However, its influence on olfactory function is unclear.
OBJECTIVES
To investigate the mechanism and the effect of repeated formaldehyde inhalation exposure on olfactory function.
METHODS
Rats were treated with formaldehyde inhalation (13·5±1·5 ppm, twice 30 minutes/day) for 14 days. Buried food pellet and locomotive activity tests were used to detect olfactory function and locomotion. Western blots were used to evaluate synaptosomal-associated protein 25 (SNAP25) protein levels in the olfactory bulb (OB) lysate and synaptosome, as well as mature and immature olfactory sensory neuron markers, olfactory marker protein (OMP), and Tuj-1. Real-time polymerase chain reaction (PCR) was used to detect SNAP25 mRNA amounts.
RESULTS
Repeated formaldehyde inhalation exposure impaired olfactory function, whereas locomotive activities were unaffected. SNAP25 protein decreased significantly in the OB, but not in the occipital lobe. SNAP25 also decreased in the OB synaptosome when synaptophysin did not change after formaldehyde treatment. mRNA levels of SNAP25A and SNAP25B were unaffected. Mature and immature olfactory sensory neuron marker, OMP, and Tuj-1, did not change after formaldehyde treatment.
CONCLUSION
Repeated formaldehyde exposure impaired olfactory function by disturbing SNAP25 protein in the OB.
Topics: Animals; Blotting, Western; Formaldehyde; Inhalation Exposure; Male; Motor Activity; Olfactory Bulb; Rats; Rats, Sprague-Dawley; Real-Time Polymerase Chain Reaction; Smell; Synaptosomal-Associated Protein 25
PubMed: 25131264
DOI: 10.1179/2049396714Y.0000000079 -
Pediatric Radiology Sep 2019We describe association of olfactory bulb and olfactory tract abnormalities in a child with acrocallosal syndrome caused by kinesin family membrane 7 (KIF7) mutation in...
We describe association of olfactory bulb and olfactory tract abnormalities in a child with acrocallosal syndrome caused by kinesin family membrane 7 (KIF7) mutation in sonic hedgehog pathway. The child also had fontanellar bone in the anterior fontanelle, short sagittal suture, sagittal synostosis, hippocampal malrotation and Joubert malformation. Fontanellar bone has been described in GLI3 mutation and mutant mice models but has not been reported in KIF7 mutation. We briefly review the role of sonic hedgehog pathway and its components KIF7 and GLI3 in forebrain and olfactory system development and also describe olfactory system abnormality in a child with GLI3 mutation.
Topics: Abnormalities, Multiple; Acrocallosal Syndrome; Acrocephalosyndactylia; Brain; Child, Preschool; Female; Humans; Infant; Magnetic Resonance Imaging; Olfactory Bulb; Tomography, X-Ray Computed
PubMed: 31399769
DOI: 10.1007/s00247-019-04480-8 -
Cellular and Molecular Life Sciences :... Mar 2017The mammalian olfactory bulb is a forebrain structure just one synapse downstream from the olfactory sensory neurons and performs the complex computations of sensory... (Review)
Review
The mammalian olfactory bulb is a forebrain structure just one synapse downstream from the olfactory sensory neurons and performs the complex computations of sensory inputs. The formation of this sensory circuit is shaped through activity-dependent and cell-intrinsic mechanisms. Recent studies have revealed that cell-type specific connectivity and the organization of synapses in dendritic compartments are determined through cell-intrinsic programs already preset in progenitor cells. These progenitor programs give rise to subpopulations within a neuron type that have distinct synaptic organizations. The intrinsically determined formation of distinct synaptic organizations requires factors from contacting cells that match the cell-intrinsic programs. While certain genes control wiring within the newly generated neurons, other regulatory genes provide intercellular signals and are only expressed in neurons that will form contacts with the newly generated cells. Here, the olfactory system has provided a useful model circuit to reveal the factors regulating assembly of the highly structured connectivity in mammals.
Topics: Animals; Humans; Mammals; Nerve Net; Neurogenesis; Neurons; Olfactory Bulb; Transcription, Genetic
PubMed: 27695873
DOI: 10.1007/s00018-016-2367-y -
AJNR. American Journal of Neuroradiology Aug 2022This study aimed to assess the utility of DTI in the detection of olfactory bulb dysfunction in COVID-19-related anosmia. It was performed in 62 patients with...
This study aimed to assess the utility of DTI in the detection of olfactory bulb dysfunction in COVID-19-related anosmia. It was performed in 62 patients with COVID-19-related anosmia and 23 controls. The mean diffusivity and fractional anisotropy were calculated by 2 readers. The difference between the fractional anisotropy and mean diffusivity values of anosmic and control olfactory bulbs was statistically significant ( = .001). The threshold of fractional anisotropy and mean diffusivity to differentiate a diseased from normal olfactory bulb were 0.22 and 1.5, with sensitivities of 84.4% and 96.8%, respectively, and a specificity of 100%.
Topics: Humans; Anosmia; Olfactory Bulb; COVID-19; Pilot Projects; Diffusion Magnetic Resonance Imaging
PubMed: 36920776
DOI: 10.3174/ajnr.A7590 -
Brain Research Bulletin Jun 2021Social memory (SM) is a key element in social cognition and it encompasses the neural representation of conspecifics, an essential information to guide behavior in a... (Review)
Review
Social memory (SM) is a key element in social cognition and it encompasses the neural representation of conspecifics, an essential information to guide behavior in a social context. Here we evaluate classical and cutting-edge studies on neurobiology of SM, using as a guiding principle behavioral tasks performed in adult rodents. Our review highlights the relevance of the hippocampus, especially the CA2 region, as a neural substrate for SM and suggest that neural ensembles in the olfactory bulb may also encode SM traces. Compared to other hippocampus-dependent memories, much remains to be done to describe the neurobiological foundations of SM. Nonetheless, we argue that special attention should be paid to neurogenesis. Finally, we pinpoint the remaining open question on whether the hippocampal adult neurogenesis acts through pattern separation to permit the discrimination of highly similar stimuli during behavior.
Topics: Animals; Hippocampus; Memory; Neurogenesis; Olfactory Bulb; Social Behavior
PubMed: 33753208
DOI: 10.1016/j.brainresbull.2021.03.006