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Neurological Sciences : Official... Jul 2022We aimed to determine how odor pathways in the stroke were affected. Measurements were performed by magnetic resonance imaging (MRI).
OBJECTIVES
We aimed to determine how odor pathways in the stroke were affected. Measurements were performed by magnetic resonance imaging (MRI).
METHODS
Cranial MRI images of 82 adult patients were included. Group 1 was consisted of 41 patients with stroke. The control group (Group 2) was consisted of 41 patients without stroke. In both groups, peripheral (OB volume and olfactory sulcus (OS) depth) and central smell areas (insular gyrus area and corpus amygdala area) were measured by MRI.
RESULTS
Peripheral and central smell regions were smaller in the stroke group compared to the control group, whereas right and left side measurements were not different. There were positive correlations between measurements of the peripheral and central smell regions. In older patients with stroke, left OB volume and bilateral OS depths, bilateral insular gyrus areas and bilateral corpus amygdala areas decreased. As the duration of stroke increased, left OB volume decreased. In males with stroke, left OB volume was lower than the females with stroke. Linear regression analysis (backward) showed that in longer stroke duration, OB-volume_R increased and OB volume_L decreased. In older patients, corpus amygdala area_R decreased. In females, OB volume_L increased.
CONCLUSION
Both central and peripheral odor pathways were affected, and left OB in the peripheral odor pathways was even more affected in case of longer duration of the stroke. Changes in central and peripheral olfactory pathways in patients with stroke may not be aimed at neuroplasticity and repair, but rather may be a reflection of inflammation and degenerative changes in stroke.
Topics: Adult; Aged; Female; Humans; Magnetic Resonance Imaging; Male; Olfaction Disorders; Olfactory Bulb; Smell; Stroke
PubMed: 35182275
DOI: 10.1007/s10072-022-05960-w -
Frontiers in Aging Neuroscience 2023The correlation between gut microbiota and Alzheimer's disease (AD) is increasingly being recognized by clinicians. However, knowledge about the gut-brain-cognition...
BACKGROUND
The correlation between gut microbiota and Alzheimer's disease (AD) is increasingly being recognized by clinicians. However, knowledge about the gut-brain-cognition interaction remains largely unknown.
METHODS
One hundred and twenty-seven participants, including 35 normal controls (NCs), 62 with subjective cognitive decline (SCD), and 30 with cognitive impairment (CI), were included in this study. The participants underwent neuropsychological assessments and fecal microbiota analysis through 16S ribosomal RNA (rRNA) Illumina Miseq sequencing technique. Structural MRI data were analyzed for cortical anatomical features, including thickness, sulcus depth, fractal dimension, and Toro's gyrification index using the SBM method. The association of altered gut microbiota among the three groups with structural MRI metrics and cognitive function was evaluated. Furthermore, co-expression network analysis was conducted to investigate the gut-brain-cognition interactions.
RESULTS
The abundance of , and decreased with cognitive ability. , and were specifically enriched in the CI group. abundance was correlated with changes in brain gray matter and cerebrospinal fluid volume ( = 0.0214, = 0.0162) and significantly with changes in cortical structures in brain regions, such as the internal olfactory area and the parahippocampal gyrus. The three colonies enriched in the CI group were positively correlated with cognitive function and significantly associated with changes in cortical structure related to cognitive function, such as the precuneus and syrinx gyrus.
CONCLUSION
This study provided evidence that there was an inner relationship among the altered gut microbiota, brain atrophy, and cognitive decline. Targeting the gut microbiota may be a novel therapeutic strategy for early AD.
PubMed: 37520126
DOI: 10.3389/fnagi.2023.1216509 -
Frontiers in Cellular Neuroscience 2023Translocator protein (TSPO), a 18 kDa protein found in the outer mitochondrial membrane, has historically been associated with the transport of cholesterol in highly... (Review)
Review
Translocator protein (TSPO), a 18 kDa protein found in the outer mitochondrial membrane, has historically been associated with the transport of cholesterol in highly steroidogenic tissues though it is found in all cells throughout the mammalian body. TSPO has also been associated with molecular transport, oxidative stress, apoptosis, and energy metabolism. TSPO levels are typically low in the central nervous system (CNS), but a significant upregulation is observed in activated microglia during neuroinflammation. However, there are also a few specific regions that have been reported to have higher TSPO levels than the rest of the brain under normal conditions. These include the dentate gyrus of the hippocampus, the olfactory bulb, the subventricular zone, the choroid plexus, and the cerebellum. These areas are also all associated with adult neurogenesis, yet there is no explanation of TSPO's function in these cells. Current studies have investigated the role of TSPO in microglia during neuron degeneration, but TSPO's role in the rest of the neuron lifecycle remains to be elucidated. This review aims to discuss the known functions of TSPO and its potential role in the lifecycle of neurons within the CNS.
PubMed: 37416505
DOI: 10.3389/fncel.2023.1210205 -
Rhinology Oct 2023Olfactory capacity increases during the period of ovulation, perhaps as an adjunct to mate selection; however, researchers have yet to elucidate the neural underpinning...
BACKGROUND
Olfactory capacity increases during the period of ovulation, perhaps as an adjunct to mate selection; however, researchers have yet to elucidate the neural underpinning of menstrual cycle-dependent variations in olfactory performance.
METHODOLOGY
A cohort of healthy volunteers (n = 88, grand cohort) underwent testing for gonadal hormone levels and resting-state functional magnetic resonance imaging with a focus on intrinsic functional connectivity (FC) in the olfactory network based on a priori seeds (piriform cortex and orbitofrontal cortex) during the periovulatory (POV) and menstrual (MEN) phases. A subcohort (n = 20, olfaction cohort) returned to the lab to undergo testing of olfactory performance during the POV and MEN phases of a subsequent menstrual cycle.
RESULTS
Olfactory performance and FC were both stronger in the periovulatory phase than in the menstrual phase. Enhanced FC was observed in the network targeting the cerebellum in both the grand and olfaction cohorts, while enhanced FC was observed in the middle temporal gyrus, lingual gyrus, dorsal medial prefrontal cortex, and postcentral gyrus in the grand cohort. Periovulatory progesterone levels in the grand cohort were positively correlated with FC in the network targeting the insula and paracentral lobule.
CONCLUSIONS
Our analysis revealed that superior olfactory function in the periovulatory period is associated with enhanced intrinsic connectivity in the olfactory network. These findings can be appreciated in the context of evolutionary biology.
Topics: Female; Humans; Smell; Menstrual Cycle; Magnetic Resonance Imaging; Brain
PubMed: 37000430
DOI: 10.4193/Rhin22.472 -
Brain Sciences Apr 2023Alzheimer's disease (AD) is associated with the abnormal connection of functional networks. Olfactory impairment occurs in early AD; therefore, exploring alterations in...
Alzheimer's disease (AD) is associated with the abnormal connection of functional networks. Olfactory impairment occurs in early AD; therefore, exploring alterations in olfactory-related regions is useful for early AD diagnosis. We combined the graph theory of local brain network topology with olfactory performance to analyze the differences in AD brain network characteristics. A total of 23 patients with AD and 18 normal controls were recruited for resting-state functional magnetic resonance imaging (fMRI), clinical neuropsychological examinations and the University of Pennsylvania Smell Identification Test (UPSIT). Between-group differences in the topological properties of the local network were compared. Pearson correlations were explored based on differential brain regions and olfactory performance. Statistical analysis revealed a correlation of the degree of cognitive impairment with olfactory recognition function. Local node topological properties were significantly altered in many local brain regions in the AD group. The nodal clustering coefficients of the bilateral temporal pole: middle temporal gyrus (TPOmid), degree centrality of the left insula (INS.L), degree centrality of the right middle temporal gyrus (MTG.R), and betweenness centrality of the left middle temporal gyrus (MTG.L) were related to olfactory performance. Alterations in local topological properties combined with the olfactory impairment can allow early identification of abnormal olfactory-related regions, facilitating early AD screening.
PubMed: 37190596
DOI: 10.3390/brainsci13040631 -
NeuroImage Apr 2021The human sense of smell is highly individual and characterized by a strong variability in the perception and evaluation of olfactory stimuli, depending on cultural...
INTRO
The human sense of smell is highly individual and characterized by a strong variability in the perception and evaluation of olfactory stimuli, depending on cultural imprint and current physiological conditions. Since this individual perspective has often been neglected in fMRI studies on olfactory hedonic coding, this study focuses on the neuronal activity and connectivity patterns resulting from subject-specific olfactory stimulation.
METHODS
Thirty-one normosmic participants took part in a fMRI block designed paradigm consisting of three olfactory stimulation sessions. The most pleasant and unpleasant odors were individually specified during a pre-test for each participant and validated in the main experiment. Mean activation and functional connectivity analysis focusing on the right and left piriform cortex were performed for the predefined olfactory regions-of-interest (ROIs) and compared between the three olfactory conditions.
RESULTS
Individual unpleasant olfactory stimulation as compared to pleasant or neutral did not alter mean BOLD activation in the predefined olfactory ROIs but led to a change in connectivity pattern in the right piriform cortex.
CONCLUSION
Our data suggests that the individual pleasantness of odors is not detectable by average BOLD magnitude changes in primary or secondary olfactory brain areas, but reflected in temporal patterns of joint activation that create a network between the right piriform cortex, the left insular cortex, the orbitofrontal cortex, and the precentral gyrus. This network may serve the evolutionary defense mechanism of olfaction by preparing goal-directed action.
Topics: Adolescent; Adult; Brain; Female; Humans; Individuality; Magnetic Resonance Imaging; Male; Nerve Net; Odorants; Olfactory Perception; Oxygen Consumption; Young Adult
PubMed: 33497777
DOI: 10.1016/j.neuroimage.2021.117782 -
Frontiers in Allergy 2022Currently, clinical assessment of olfaction is largely reliant on subjective methods that require patient participation. The objective method for measuring olfaction,...
IMPORTANCE
Currently, clinical assessment of olfaction is largely reliant on subjective methods that require patient participation. The objective method for measuring olfaction, using electroencephalogram (EEG) readings, can be supplemented with the improved temporal resolution of magnetoencephalography (MEG) for olfactory measurement that can delineate cortical and peripheral olfactory loss. MEG provides high temporal and spatial resolution which can enhance our understanding of central olfactory processing compared to using EEG alone.
OBJECTIVE
To determine the feasibility of building an in-house portable olfactory stimulator paired with electrophysiological neuroimaging technique with MEG to assess olfaction in the clinical setting.
DESIGN SETTING AND PARTICIPANTS
This proof-of-concept study utilized a paired MEG-olfactometer paradigm to assess olfaction in three normosmic participants. We used a two-channel olfactory stimulator to deliver odorants according to a programmed stimulus-rest paradigm. Two synthetic odorants: 2% phenethyl alcohol (rose) and 0.5% amyl acetate (banana) were delivered in increasing increments of time followed by periods of rest. Cortical activity was measured a 306-channel MEG system.
MAIN OUTCOMES AND MEASURES
Primary outcome measure was the relative spectral power for each frequency band, which was contrasted between rest and olfactory stimulation.
RESULTS
Compared to rest, olfactory stimulation produced a 40% increase in relative alpha power within the olfactory cortex bilaterally with both odorants. A 25%-30% increase in relative alpha power occurred in the left orbitofrontal cortex and precentral gyrus with phenethyl alcohol stimulation but not amyl acetate.
CONCLUSION AND RELEVANCE
In this proof-of-concept study, we demonstrate the feasibility of olfactory measurement an olfactometer-MEG paradigm. We found that odorant-specific cortical signatures can be identified using this paradigm, setting the basis for further investigation of this system as a prognostic tool for olfactory loss.
PubMed: 36698377
DOI: 10.3389/falgy.2022.1019265 -
Journal of Neurological Surgery. Part... Oct 2021We investigated the effects of vitamin D deficiency in the peripheral and central smell regions by magnetic resonance imaging (MRI). This retrospective study...
We investigated the effects of vitamin D deficiency in the peripheral and central smell regions by magnetic resonance imaging (MRI). This retrospective study included 29 patients (12 males, 17 females) with 25-dihydroxy vitamin D3 [25(OH) D ] deficiency (group 1) and 34 subjects without 25(OH) D deficiency (14 males, 20 females) (group 2). Using cranial MRIs, the peripheral (olfactory bulb [OB] volume and olfactory sulcus [OS] depth) and central (insular gyrus and corpus amygdala) smell regions were evaluated. The OB volume and OS depth values of the 25(OH) D3 deficiency group were significantly lower than those of the control group ( < 0.05). For the central smell regions, the insular gyrus and corpus amygdala areas of the 25(OH) D3 deficiency group were nonsignificantly lower than those in the control group ( > 0.05). There were positive correlations between OB volumes, OS depths, and insular gyrus and corpus amygdala areas bilaterally in the 25(OH) D3 deficiency group separately and in all subjects (groups 1 and 2) ( < 0.05). In the 25(OH) D3 deficiency group, as the 25(OH) D3 values became lower, the insular gyrus area values decreased bilaterally ( < 0.05). In females, the corpus amygdala area values were lower than in males ( < 0.05). Since vitamin D3 deficiency affected the peripheral and central smell regions negatively, we recommend evaluating patients' vitamin D levels as a health policy to prevent vitamin D3 deficiency-related cranial smell region problems. Moreover, sunlight exposure is very important to increase vitamin D levels, and the public should be informed about this topic.
PubMed: 34513566
DOI: 10.1055/s-0040-1722227 -
Obesity (Silver Spring, Md.) Jul 2021Food odors serve as powerful stimuli signaling the food quality and energy density and direct food-specific appetite and consumption. This study explored obesity-related...
OBJECTIVE
Food odors serve as powerful stimuli signaling the food quality and energy density and direct food-specific appetite and consumption. This study explored obesity-related brain activation in response to odors related to high- or low-energy-dense foods.
METHODS
Seventeen participants with obesity (BMI > 30 kg/m ; 4 males and 13 females) and twenty-one with normal weight (BMI < 25 kg/m ; 9 males and 12 females) underwent a functional magnetic resonance imaging scan in which they received chocolate (high-energy-dense food) and cucumber (low-energy-dense food) odor stimuli. Participants' olfactory and gustatory functions were assessed by the "Sniffin' Sticks" and "Taste Strips" tests, respectively.
RESULTS
Compared with normal-weight controls, participants with obesity had lower odor sensitivity (phenylethyl alcohol) and decreased odor discrimination ability. However, participants with obesity demonstrated greater brain activation in response to chocolate compared with cucumber odors in the bilateral inferior frontal operculum and cerebellar vermis, right ventral anterior insula extending to putamen, right middle temporal gyrus, and right supramarginal areas.
CONCLUSIONS
The present study provides preliminary evidence that obesity is associated with heightened brain activation of the reward and flavor processing areas in response to chocolate versus cucumber odors, possibly because of the higher energy density and reinforcing value of chocolate compared with cucumber.
Topics: Brain; Brain Mapping; Female; Humans; Magnetic Resonance Imaging; Male; Obesity; Odorants; Reward
PubMed: 33913254
DOI: 10.1002/oby.23170 -
Scientific Reports Aug 2023We aimed to investigate changes in olfactory bulb volume and brain network in the white matter (WM) in patients with persistent olfactory disfunction (OD) following...
We aimed to investigate changes in olfactory bulb volume and brain network in the white matter (WM) in patients with persistent olfactory disfunction (OD) following COVID-19. A cross-sectional study evaluated 38 participants with OD after mild COVID-19 and 24 controls, including Sniffin' Sticks identification test (SS-16), MoCA, and brain magnetic resonance imaging. Network-Based Statistics (NBS) and graph theoretical analysis were used to explore the WM. The COVID-19 group had reduced olfactory bulb volume compared to controls. In NBS, COVID-19 patients showed increased structural connectivity in a subnetwork comprising parietal brain regions. Regarding global network topological properties, patients exhibited lower global and local efficiency and higher assortativity than controls. Concerning local network topological properties, patients had reduced local efficiency (left lateral orbital gyrus and pallidum), increased clustering (left lateral orbital gyrus), increased nodal strength (right anterior orbital gyrus), and reduced nodal strength (left amygdala). SS-16 test score was negatively correlated with clustering of whole-brain WM in the COVID-19 group. Thus, patients with OD after COVID-19 had relevant WM network dysfunction with increased connectivity in the parietal sensory cortex. Reduced integration and increased segregation are observed within olfactory-related brain areas might be due to compensatory plasticity mechanisms devoted to recovering olfactory function.
Topics: Humans; Diffusion Tensor Imaging; Cross-Sectional Studies; COVID-19; Brain; White Matter; Magnetic Resonance Imaging
PubMed: 37558765
DOI: 10.1038/s41598-023-40115-7