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Laryngo- Rhino- Otologie Aug 2007Olfactory dysfunction has been reported to affect about 79,000 patients who were treated annually in German ORL-hospitals. The incidence of olfactory dysfunctions... (Review)
Review
Olfactory dysfunction has been reported to affect about 79,000 patients who were treated annually in German ORL-hospitals. The incidence of olfactory dysfunctions emphasizes the need for diagnostic strategies. This article features on the dysfunction of human olfaction including neurodegenerative diseases. Standard procedures for the psychophysical and objective assessment of olfactory function are presented. Current diagnostic imaging techniques for routine use and scientific approaches are discussed.
Topics: Adrenal Cortex Hormones; Amygdala; Chemoreceptor Cells; Electroencephalography; Equipment Design; Evoked Potentials; Gyrus Cinguli; Humans; Magnetic Resonance Imaging; Neurodegenerative Diseases; Olfaction Disorders; Olfactory Nerve Diseases; Olfactory Pathways; Otolaryngology; Sensory Thresholds; Smell; Tomography, X-Ray Computed; Trigeminal Nerve
PubMed: 17665356
DOI: 10.1055/s-2007-966532 -
Genes To Cells : Devoted To Molecular &... Oct 2006Neurogenesis in the subgranular zone of the hippocampal dentate gyrus and olfactory bulbs continues into adulthood and has been implicated in the cognitive function of...
Neurogenesis in the subgranular zone of the hippocampal dentate gyrus and olfactory bulbs continues into adulthood and has been implicated in the cognitive function of the adult brain. The basal forebrain cholinergic system has been suggested to play a role in regulating neurogenesis as well as learning and memory in these regions. Herein, we report that highly polysialylated neural cell adhesion molecule (PSA-NCAM)-positive immature cells as well as neuronal nuclei (NeuN)-positive mature neurons in the dentate gyrus and olfactory bulb express multiple acetylcholine receptor subunits and make contact with cholinergic fibers. To examine the function of acetylcholine in neurogenesis, we used donepezil (Aricept), a potent and selective acetylcholinesterase inhibitor that improves cognitive impairment in Alzheimer's disease. Intraperitoneal administrations of donepezil significantly enhanced the survival of newborn neurons, but not proliferation of neural progenitor cells in the subgranular zone or the subventricular zone of normal mice. Moreover, donepezil treatment reversed the chronic stress-induced decrease in neurogenesis. Taken together, these results suggest that activation of the cholinergic system promotes survival of newborn neurons in the adult dentate gyrus and olfactory bulb under both normal and stressed conditions.
Topics: Acetylcholine; Animals; Animals, Newborn; Cell Survival; Cholinergic Fibers; Cholinesterase Inhibitors; Dentate Gyrus; Donepezil; Humans; Indans; Male; Mice; Mice, Inbred C57BL; Neurons; Olfactory Bulb; Piperidines; Receptors, Cholinergic
PubMed: 16999735
DOI: 10.1111/j.1365-2443.2006.01010.x -
Molecular Neurobiology Jun 2023Parkinson's disease (PD) is the second most common neurodegenerative disorder affecting the body and mind of millions of people in the world. As PD progresses,...
Restoration of Adult Neurogenesis by Intranasal Administration of Gangliosides GD3 and GM1 in The Olfactory Bulb of A53T Alpha-Synuclein-Expressing Parkinson's-Disease Model Mice.
Parkinson's disease (PD) is the second most common neurodegenerative disorder affecting the body and mind of millions of people in the world. As PD progresses, bradykinesia, rigidity, and tremor worsen. These motor symptoms are associated with the neurodegeneration of dopaminergic neurons in the substantia nigra. PD is also associated with non-motor symptoms, including loss of smell (hyposmia), sleep disturbances, depression, anxiety, and cognitive impairment. This broad spectrum of non-motor symptoms is in part due to olfactory and hippocampal dysfunctions. These non-motor functions are suggested to be linked with adult neurogenesis. We have reported that ganglioside GD3 is required to maintain the neural stem cell (NSC) pool in the subventricular zone (SVZ) of the lateral ventricles and the subgranular layer of the dentate gyrus (DG) in the hippocampus. In this study, we used nasal infusion of GD3 to restore impaired neurogenesis in A53T alpha-synuclein-expressing mice (A53T mice). Intriguingly, intranasal GD3 administration rescued the number of bromodeoxyuridine + (BrdU +)/Sox2 + NSCs in the SVZ. Furthermore, the administration of gangliosides GD3 and GM1 increases doublecortin (DCX)-expressing immature neurons in the olfactory bulb, and nasal ganglioside administration recovered the neuronal populations in the periglomerular layer of A53T mice. Given the relevance of decreased ganglioside on olfactory impairment, we discovered that GD3 has an essential role in olfactory functions. Our results demonstrated that intranasal GD3 infusion restored the self-renewal ability of the NSCs, and intranasal GM1 infusion promoted neurogenesis in the adult brain. Using a combination of GD3 and GM1 has the potential to slow down disease progression and rescue dysfunctional neurons in neurodegenerative brains.
Topics: Mice; Animals; alpha-Synuclein; Parkinson Disease; G(M1) Ganglioside; Olfactory Bulb; Administration, Intranasal; Gangliosides; Neurogenesis; Dopaminergic Neurons
PubMed: 36849668
DOI: 10.1007/s12035-023-03282-2 -
Annals of Clinical and Translational... Feb 2023This research aims to study structural brain changes in patients with persistent olfactory dysfunctions after coronavirus disease 2019 (COVID-19).
OBJECTIVE
This research aims to study structural brain changes in patients with persistent olfactory dysfunctions after coronavirus disease 2019 (COVID-19).
METHODS
COVID-19 patients were evaluated using T1-weighted and diffusion tensor imaging (DTI) on a 3T MRI scanner, 9.94 ± 3.83 months after COVID-19 diagnosis. Gray matter (GM) voxel-based morphometry was performed using FSL-VBM. Voxelwise statistical analysis of the fractional anisotropy, mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity was carried out with the tract-based spatial statistics in the olfactory system. The smell identification test (UPSIT) was used to classify patients as normal olfaction or olfactory dysfunction groups. Intergroup comparisons between GM and DTI measures were computed, as well as correlations with the UPSIT scores.
RESULTS
Forty-eight COVID-19 patients were included in the study. Twenty-three were classified as olfactory dysfunction, and 25 as normal olfaction. The olfactory dysfunction group had lower GM volume in a cluster involving the left amygdala, insular cortex, parahippocampal gyrus, frontal superior and inferior orbital gyri, gyrus rectus, olfactory cortex, caudate, and putamen. This group also showed higher MD values in the genu of the corpus callosum, the orbitofrontal area, the anterior thalamic radiation, and the forceps minor; and higher RD values in the anterior corona radiata, the genu of the corpus callosum, and uncinate fasciculus compared with the normal olfaction group. The UPSIT scores for the whole sample were negatively associated with both MD and RD values (p-value ≤0.05 FWE-corrected).
INTERPRETATION
There is decreased GM volume and increased MD in olfactory-related regions explaining prolonged olfactory deficits in post-acute COVID-19 patients.
Topics: Humans; Smell; Diffusion Tensor Imaging; COVID-19 Testing; COVID-19; Brain; Olfaction Disorders
PubMed: 36525472
DOI: 10.1002/acn3.51710 -
Clinical Radiology Feb 2024To investigate peripheral and central olfactory pathways using cranial magnetic resonance imaging (MRI) in human immunodeficiency virus (HIV)-infected patients.
AIM
To investigate peripheral and central olfactory pathways using cranial magnetic resonance imaging (MRI) in human immunodeficiency virus (HIV)-infected patients.
MATERIALS AND METHODS
The cranial MRI images of 37 HIV-infected adult patients and 37 adults without HIV infection having normal cranial MRI results were included in the study. In both groups, olfactory bulb (OB) volume and olfactory sulcus (OS) depth; and insular gyrus and corpus amygdala areas were measured using cranial MRI. In the HIV group, disease duration, HIV RNA, and CD4 lymphocyte count and levels as a percentage were also recorded.
RESULTS
The HIV group had significantly lower bilateral OB volumes, insular gyrus and corpus amygdala areas compared to the control group. The HIV group showed positive correlations between OB volumes, OS depths, insular gyrus, and corpus amygdala areas bilaterally. Increases in OB volumes and OS depths were associated with an increase in the insular gyrus area. The corpus amygdala and insular gyrus areas increased similarly. There was no significant correlation between age, gender, disease duration, CD4 lymphocyte count and per cent, HIV RNA values, and the measurement values of the central and peripheral olfactory regions.
CONCLUSION
A decrease in olfactory regions of OB, insular gyrus, and corpus amygdala in HIV-infected patients shows that HIV infection may cause olfactory impairment. There is no correlation between disease duration and olfactory impairment. It may be related to neuroinflammation, HIV-related brain atrophy, acquired immunodeficiency syndrome (AIDS) dementia complex, or neurocognitive impairment, which are the other explanations for the olfactory impairment in HIV. The possible toxicity from antiretroviral therapy (ART) may be another cause that should be investigated further.
Topics: Adult; Humans; HIV; Olfactory Pathways; HIV Infections; Magnetic Resonance Imaging; Olfaction Disorders; RNA
PubMed: 38030506
DOI: 10.1016/j.crad.2023.10.035 -
Human Brain Mapping Jun 2018Removal of the olfactory bulb (OB) leads to depression like behavior in rodents. A link between depression and olfactory function is also established in humans. We...
BACKGROUND
Removal of the olfactory bulb (OB) leads to depression like behavior in rodents. A link between depression and olfactory function is also established in humans. We hypothesized that the human OB volume relates to depressive state and tested whether such a potential coherence is moderated by structural alterations in other brain regions.
METHODS
Eighty-three participants (32 patients with major depression and 51 matched healthy controls) underwent structural MR scanning. Individual OB volumes were compared between patients and controls and the impact of depression and comorbidity was analyzed with multiple regression analysis. Whole-brain voxel-based morphometry revealed structures co-varying with both depressive state and OB volume.
RESULTS
The OB volume of patients was significantly reduced and this reduction averaged out at 17% compared to the controls. The OB volume was correlated to the volume of the insula, superior temporal cortex, and amygdala. The independent variables of depression (β = -.37), age (β = -.25), and gender (β = -.40) explained the individual OB volume variation (R = .37). The correlation between OB volume and depression was moderated by volumetric reductions in a cluster including the insula and superior temporal gyrus (STG).
CONCLUSIONS
The OB volume relates to depression in humans and to the volume of structures which are critical for salience detection. We assume that a reduced OB volume causes diminished neural olfactory input which facilitates volume reduction in the insula and STG. The OB volume may hence constitute a factor of vulnerability to depression. Olfactory-based deep brain stimulation is discussed as a future therapeutic approach.
Topics: Adult; Analysis of Variance; Brain Mapping; Case-Control Studies; Depression; Female; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Male; Middle Aged; Olfactory Bulb; Regression Analysis; Surveys and Questionnaires
PubMed: 29493048
DOI: 10.1002/hbm.24024 -
Chemical Senses Jan 2023Little is known about the neural basis of lower- and higher-order olfactory functions such as odor memory, compared with other sensory systems. The aim of this study was...
Little is known about the neural basis of lower- and higher-order olfactory functions such as odor memory, compared with other sensory systems. The aim of this study was to explore neural networks and correlates associated with 3 functions: passive smelling (PS), odor encoding (OE), and in particular odor recognition memory (ORM). Twenty-six healthy participants were examined using functional magnetic resonance imaging conducted across 3 sessions, one for each function. Independent component analysis revealed a difference between sessions where a distinct ORM component incorporating hippocampus and posterior cingulate showed delayed triggering dissociated from odor stimulation and recognition. By contrasting Hit for ORM (target odors correctly recognized as old) and a combination of PS and detected odors from OE, we found significantly lower activations in amygdala, piriform cortex, insula, thalamus, and the inferior parietal lobule. Region of interest analysis including anterior insula, posterior cingulate gyrus, dentate gyrus, left middle frontal gyrus, amygdala, and piriform cortex demonstrated that Hit were associated with lower activations compared with other memory responses. In summary, our findings suggest that successful recognition of familiar odors (odor familiarity) is associated with neural suppression in the abovementioned regions of interest. Additionally, network including the hippocampus and posterior cingulate is engaged in a postrecognition process. This process may be related to incidental encoding of less familiar and more novel odors (odor novelty) and should be subject for future research.
Topics: Humans; Odorants; Smell; Recognition, Psychology; Hippocampus; Amygdala; Magnetic Resonance Imaging; Brain; Brain Mapping
PubMed: 36715106
DOI: 10.1093/chemse/bjad001 -
Brain Research Sep 1995It has previously been shown that the hilus of the dentate gyrus responds to odors (e.g. toluene) with a burst of fast waves and to electrical stimulation of the...
It has previously been shown that the hilus of the dentate gyrus responds to odors (e.g. toluene) with a burst of fast waves and to electrical stimulation of the olfactory bulb with an evoked potential consisting of an early component immediately after the stimulus artifact, a second component with a 16-18-ms latency and additional late components. Spectral analysis revealed that odor-induced fast-wave bursts in the olfactory bulb and dentate gyrus both had a peak frequency of 15-20 Hz and were highly coherent. Unilateral intrahippocampal injections of colchicine or kainic acid were used in an attempt to destroy granule and pyramidal cells, respectively, while saline was injected on the opposite side as a control. Recordings from chronically implanted electrodes in the olfactory bulb and dentate gyrus demonstrated that saline had no effect while either neurotoxin abolished the odor-induced fast waves. In addition, the late 16-18-ms component of the dentate-evoked potentials after single-pulse stimulation of the olfactory bulb was abolished by either kainic acid or colchicine; the early dentate response, probably a volume-conducted olfactory response, was not abolished. Histological analysis indicated that kainic acid produced widespread non-specific damage in the hippocampal formation. Kainic acid-treated tissue exhibits a thinning of granule cell and molecular layers of the dentate gyrus as well as cell loss in CA3 and part of CA1.
Topics: Animals; Behavior, Animal; Colchicine; Dentate Gyrus; Electric Stimulation; Electroencephalography; Evoked Potentials; Fourier Analysis; Functional Laterality; Kainic Acid; Male; Odorants; Olfactory Bulb; Olfactory Pathways; Rats
PubMed: 8535832
DOI: 10.1016/0006-8993(95)00571-7 -
NeuroImage Mar 2013The human brain's ability to adapt to environmental changes is obvious in specific sensory domains of experts, and olfaction is one of the least investigated senses. As...
The human brain's ability to adapt to environmental changes is obvious in specific sensory domains of experts, and olfaction is one of the least investigated senses. As we have previously demonstrated that olfactory expertise is related to functional brain modifications, we investigated here whether olfactory expertise is also coupled with structural changes. We used voxel-based morphometry to compare the gray-matter volume in student and professional perfumers, as well as untrained control subjects, and accounted for all methodological improvements that have been recently developed to limit possible errors associated with image processing. In all perfumers, we detected an increase in gray-matter volume in the bilateral gyrus rectus/medial orbital gyrus (GR/MOG), an orbitofrontal area that surrounds the olfactory sulcus. In addition, gray-matter volume in the anterior PC and left GR/MOG was positively correlated with experience in professional perfumers. We concluded that the acute olfactory knowledge acquired through extensive olfactory training leads to the structural reorganization of olfactory brain areas.
Topics: Adult; Brain; Brain Mapping; Female; Humans; Image Interpretation, Computer-Assisted; Magnetic Resonance Imaging; Male; Middle Aged; Olfactory Perception; Perfume; Young Adult
PubMed: 23246995
DOI: 10.1016/j.neuroimage.2012.11.044 -
Neuron Jul 2020Animals must discern important stimuli and place them onto their cognitive map of their environment. The neocortex conveys general representations of sensory events to...
Animals must discern important stimuli and place them onto their cognitive map of their environment. The neocortex conveys general representations of sensory events to the hippocampus, and the hippocampus is thought to classify and sharpen the distinctions between these events. We recorded populations of dentate gyrus granule cells (DG GCs) and lateral entorhinal cortex (LEC) neurons across days to understand how sensory representations are modified by experience. We found representations of odors in DG GCs that required synaptic input from the LEC. Odor classification accuracy in DG GCs correlated with future behavioral discrimination. In associative learning, DG GCs, more so than LEC neurons, changed their responses to odor stimuli, increasing the distance in neural representations between stimuli, responding more to the conditioned and less to the unconditioned odorant. Thus, with learning, DG GCs amplify the decodability of cortical representations of important stimuli, which may facilitate information storage to guide behavior.
Topics: Animals; Association Learning; Dentate Gyrus; Male; Mice; Mice, Inbred C57BL; Neurons; Olfactory Perception
PubMed: 32359400
DOI: 10.1016/j.neuron.2020.04.002