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Frontiers in Neurology 2023To review and analyze the functional connectivity (FC) abnormalities in the brain olfactory network (ON) of patients with chronic rhinosinusitis with olfactory...
OBJECTIVE
To review and analyze the functional connectivity (FC) abnormalities in the brain olfactory network (ON) of patients with chronic rhinosinusitis with olfactory dysfunction (CRSwOD) and explore the relationship between these FC abnormalities and olfactory dysfunction, providing clues to the neurophysiological mechanisms underlying CRSwOD.
METHODS
FC analysis on the ON of patients with CRSwOD and patients with chronic rhinosinusitis without olfactory dysfunction (CRSsOD) identified the regions of the ON with abnormal FC in CRSwOD patients, and the correlation between abnormal FC and clinical scales for chronic rhinosinusitis was analyzed.
RESULTS
(1) Compared with the CRSsOD group, CRSwOD patients showed decreased FC between the bilateral orbitofrontal cortex (OFC) and the right middle frontal gyrus, (2) Receiver operating characteristic (ROC) curve analysis revealed that the FC value between the right middle frontal gyrus and the left OFC (area under the curve (AUC) = 0.852, sensitivity: 0.821, specificity: 0.800, < 0.001) was more capable of distinguishing whether CRS patients may have olfactory dysfunction than the FC value between the right middle frontal gyrus and the right OFC (AUC = 0.827, sensitivity: 0.893, specificity: 0.667, < 0.001), and (3) Lund-Kennedy scores were positively correlated with the FC values between the right middle frontal gyrus and the left OFC ( = 0.443, < 0.018). Lund-Mackay scores were also positively correlated with the FC values between the right middle frontal gyrus and the left OFC ( = 0.468, < 0.012). Questionnaire of Olfactory Disorders-Negative Statements scores were negatively correlated with the FC values between the right middle frontal gyrus and the left OFC ( = -0.481, < 0.001).
CONCLUSION
Persistent nasal inflammation affects the FC between the middle frontal gyrus and the OFC, which may serve as a potential imaging marker for identifying CRSwOD. The severity of nasal inflammation and olfactory damage is closely related to the FC between the middle frontal gyrus and OFC, and the abnormal changes in this FC can be used to explain the neurophysiological mechanisms behind the occurrence of olfactory dysfunction in patients.
PubMed: 38046577
DOI: 10.3389/fneur.2023.1295556 -
Journal of Affective Disorders Feb 2024Patients with thyroid-associated opthalmopathy (TAO) have widespread white matter (WM) abnormalities in the emotional and cognitive functional regions. However, the...
BACKGROUND
Patients with thyroid-associated opthalmopathy (TAO) have widespread white matter (WM) abnormalities in the emotional and cognitive functional regions. However, the topological representation of these WM abnormalities and the network-level structural aberrations underlying TAO and concomitant affective disorders are still unclear.
METHODS
We used probabilistic diffusion tractography and graph theory to investigate brain network topology in 37 active, 35 inactive TAO patients and 23 healthy controls. Then, we evaluated the partial correlations between network topological metrics and clinical parameters.
RESULTS
For global topology, only active TAO patients exhibited significantly decreased global (E) and local (E) efficiency compared with controls, while no significant difference was observed between active and inactive TAO patients. For regional topology, we found a significantly decreased nodal efficiency in the left orbital superior frontal gyrus (ORBsup), medial orbital superior frontal gyrus (ORBsupmed), hippocampus and amygdala in active TAO patients compared with inactive ones. Intriguingly, E, E, and nodal efficiency of left ORBsup, ORBsupmed, olfactory cortex, gyrus rectus, hippocampus, right parahippocampal gyrus and amygdala had significantly positive correlations with anxiety/depression scores, bilateral exophthalmos and intraocular pressure in active TAO patients, while no significant correlation was observed in inactive TAO patients.
LIMITATIONS
No longitudinal follow-up.
CONCLUSIONS
WM networks of TAO are characterized by decreased local specialization and global integration in the active phase, and decreased nodal efficiency highly related to anxiety and depression in the emotional and cognitive regions. Our findings provide new insight regarding the neurobiological mechanisms of TAO and contribute to the treatment of concomitant affective disorders.
Topics: Humans; Depression; Graves Ophthalmopathy; Brain; Diffusion Tensor Imaging; Anxiety
PubMed: 38042306
DOI: 10.1016/j.jad.2023.11.089 -
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 -
Diabetes, Obesity & Metabolism Mar 2024To characterize the comparative contributions of different glycaemic indicators to cognitive dysfunction, and further investigate the associations between the most...
AIMS
To characterize the comparative contributions of different glycaemic indicators to cognitive dysfunction, and further investigate the associations between the most significant indicator and cognitive function, along with related cerebral alterations.
MATERIALS AND METHODS
We performed a cross-sectional study in 449 subjects with type 2 diabetes who completed continuous glucose monitoring and cognitive assessments. Of these, 139 underwent functional magnetic resonance imaging to evaluate cerebral structure and olfactory neural circuit alterations. Relative weight and Sobol's sensitivity analyses were employed to characterize the comparative contributions of different glycaemic indicators to cognitive dysfunction.
RESULTS
Complexity of glucose time series index (CGI) was found to have a more pronounced association with mild cognitive impairment (MCI) compared to glycated haemoglobin, time in range, and standard deviation. The proportion and multivariable-adjusted odds ratios (ORs) for MCI increased with descending CGI tertile (Tertile 1: reference group [≥4.0]; Tertile 2 [3.6-4.0] OR 1.23, 95% confidence interval [CI] 0.68-2.24; Tertile 3 [<3.6] OR 2.27, 95% CI 1.29-4.00). Decreased CGI was associated with cognitive decline in executive function and attention. Furthermore, individuals with decreased CGI displayed reduced olfactory activation in the left orbitofrontal cortex (OFC) and disrupted functional connectivity between the left OFC and right posterior cingulate gyrus. Mediation analysis demonstrated that the left OFC activation partially mediated the associations between CGI and executive function.
CONCLUSION
Decreased glucose complexity closely relates to cognitive dysfunction and olfactory brain activation abnormalities in diabetes.
Topics: Adult; Humans; Diabetes Mellitus, Type 2; Glucose; Time Factors; Cross-Sectional Studies; Blood Glucose Self-Monitoring; Blood Glucose; Cognition; Cognitive Dysfunction; Magnetic Resonance Imaging; Brain
PubMed: 37994378
DOI: 10.1111/dom.15376 -
Audiology & Neuro-otology 2024The aim of the study was to investigate differences in the intra- and inter-network functional connectivity (FC) of the brain using resting-state functional magnetic...
INTRODUCTION
The aim of the study was to investigate differences in the intra- and inter-network functional connectivity (FC) of the brain using resting-state functional magnetic resonance imaging (rs-fMRI) in patients with tinnitus, with (T + H) or without hearing loss (T).
METHODS
We performed rs-fMRI on 82 participants (21 T, 32 T + H, and 29 healthy controls). An independent component analysis (ICA) was performed to obtain the resting-state networks (RSNs) and calculate the differences in FC. Moreover, we investigated the relationships between networks using functional network connectivity analysis.
RESULTS
We identified nine major RSNs, including the auditory network; default mode network; executive control network (ECN), including the right frontoparietal network and left frontoparietal network (LFPN); somatomotor network (SMN); dorsal attention network; ventral attention network; salience network (SN); and visual network (VN). These RSNs were extracted in all groups using ICA. Compared with that in the control group, we observed reduced FC between the LFPN and VN in the T group and between the LFPN and SN in the T + H group. The inter-network connectivity analysis revealed decreased network interactions in the SMN (IC 22)-ECN (IC 2), SMN (IC 22)-VN (IC 8), and VN (IC 14)-SN (IC 3) connections in the T + H group, compared with the healthy control group. Furthermore, we observed significantly decreased network interactions in the SMN (IC 22)-VN (IC 8) in the T group.
CONCLUSIONS
Our results indicated abnormalities within the brain networks of the T and T + H groups, including the SMN, ECN, and VN, compared with the control group. Furthermore, both T and T + H groups demonstrated reduced FC between the LFPN, VN, and SMN. There were no significant differences between the T and the T + H groups. Furthermore, we observed reduced FC between the right olfactory cortex and the orbital part of the right middle frontal gyrus, right precentral gyrus, left dorsolateral superior frontal gyrus, and right triangular part of the inferior frontal gyrus within the T and T + H groups. Thus, disruptions in brain regions responsible for attention, stimulus monitoring, and auditory orientation contribute to tinnitus generation.
Topics: Humans; Brain Mapping; Tinnitus; Magnetic Resonance Imaging; Brain; Hearing Loss; Deafness
PubMed: 37963433
DOI: 10.1159/000534659 -
International Journal of Molecular... Oct 2023Serotonergic neurotransmission has been associated with aggression in several psychiatric disorders. Human aggression is a continuum of traits, ranging from normal to...
In Vivo Serotonin 5-HT2A Receptor Availability and Its Relationship with Aggression Traits in Healthy Individuals: A Positron Emission Tomography Study with C-11 MDL100907.
Serotonergic neurotransmission has been associated with aggression in several psychiatric disorders. Human aggression is a continuum of traits, ranging from normal to pathological phenomena. However, the individual differences in serotonergic neurotransmission and their relationships with aggression traits in healthy individuals remain unclear. In this study, we explored the relationship between 5-HT2A receptor availability in vivo and aggression traits in healthy participants. Thirty-three healthy participants underwent 3-Tesla magnetic resonance imaging and positron emission tomography (PET) with [C]MDL100907, a selective radioligand for 5-HT2A receptors. To quantify 5-HT2A receptor availability, the binding potential (BP) was derived using the basis function implementation of the simplified reference tissue model, with the cerebellum as the reference region. The participants' aggression levels were assessed using the Buss-Perry Aggression Questionnaire. The voxel-based correlation analysis with age and sex as covariates revealed that the total aggression score was significantly positively correlated with [C]MDL100907 BP in the right middle temporal gyrus (MTG) pole, left fusiform gyrus (FUSI), right parahippocampal gyrus, and right hippocampus. The physical aggression subscale score had significant positive correlations with [C]MDL100907 BP in the left olfactory cortex, left orbital superior frontal gyrus (SFG), right anterior cingulate and paracingulate gyri, left orbitomedial SFG, left gyrus rectus, left MTG, left inferior temporal gyrus, and left angular gyrus. The verbal aggression subscale score showed significant positive correlations with [C]MDL100907 BP in the bilateral SFG, right medial SFG, left FUSI, and right MTG pole. Overall, our findings suggest the possibility of positive correlations between aggression traits and in vivo 5-HT2A receptor availability in healthy individuals. Future research should incorporate multimodal neuroimaging to investigate the downstream effects of 5-HT2A receptor-mediated signaling and integrate molecular and systems-level information in relation to aggression traits.
Topics: Humans; Aggression; Brain; Carbon Radioisotopes; Magnetic Resonance Imaging; Positron-Emission Tomography; Receptor, Serotonin, 5-HT2A; Serotonin
PubMed: 37958691
DOI: 10.3390/ijms242115697 -
Neurosurgery Apr 2024The piriform cortex (PC) is part of the primary olfactory network in humans. Recent findings suggest that it plays a role in pathophysiology of epilepsy. Therefore,...
BACKGROUND AND OBJECTIVES
The piriform cortex (PC) is part of the primary olfactory network in humans. Recent findings suggest that it plays a role in pathophysiology of epilepsy. Therefore, studying its connectivity can further our understanding of seizure propagation in epilepsy. We aimed to explore the structural connectivity of PC using high-quality human connectome project data coupled with segmentation of PC on anatomic MRI.
METHODS
Twenty subjects were randomly selected from the human connectome project database, and PC was traced on each hemisphere. Probabilistic whole-brain tractography was then used to visualize PC connectivity.
RESULTS
The strongest connectivity was noted between PC and ipsilateral insula in both hemispheres. Specifically, the posterior long gyrus of each insula was predominantly connected to PC. This was followed by connections between PC and basal ganglia as well as orbital frontal cortices.
CONCLUSION
The PC has the strongest connectivity with the insula bilaterally. Specifically, the posterior long gyri of insula have the strongest connectivity. This finding may provide additional insight for localizing and treating temporo-insular epilepsy.
Topics: Humans; Cerebral Cortex; Piriform Cortex; Epilepsy; Magnetic Resonance Imaging; Connectome; Frontal Lobe
PubMed: 37955443
DOI: 10.1227/neu.0000000000002756 -
Ageing Research Reviews Dec 2023In aging, olfactory deficits have been associated with lower cognition and motor function. Olfactory dysfunction is also one of the earliest features of... (Review)
Review
In aging, olfactory deficits have been associated with lower cognition and motor function. Olfactory dysfunction is also one of the earliest features of neurodegenerative disease. A comprehensive review of the neural correlates of olfactive function may reveal mechanisms underlying the associations among olfaction, cognition, motor function, and neurodegenerative diseases. Here, we summarize existing knowledge on the relationship between brain structural and functional measures and olfaction in older adults without and with cognitive impairment, including Alzheimer's disease. We identified 33 eligible studies (30 MRI/DTI,3 fMRI); 31 were cross-sectional, most assessed odor identification, and few examined multiple brain areas. Lower olfactory function was associated with smaller volumes in the temporal lobe (hippocampus,parahippocampal gyrus,fusiform gyrus), olfactory-related regions (piriform cortex,amygdala,entorhinal cortex), pre- and postcentral gyri, and globus pallidus. During aging, olfactory impairment may be associated with pathology in brain areas important for motor function and cognition, especially memory. Future longitudinal studies that include neuroimaging across different brain areas are warranted to determine the neurobiological changes underlying olfactory changes in the aging brain and the progression of neurodegeneration.
Topics: Humans; Aged; Neurodegenerative Diseases; Brain; Entorhinal Cortex; Hippocampus; Temporal Lobe; Magnetic Resonance Imaging; Cognitive Dysfunction
PubMed: 37913831
DOI: 10.1016/j.arr.2023.102095 -
The Journal of Clinical Endocrinology... Feb 2024To investigate the brain structural and functional alterations in patients with thyroid-associated ophthalmopathy (TAO) before and after glucocorticoid therapy, using...
OBJECTIVE
To investigate the brain structural and functional alterations in patients with thyroid-associated ophthalmopathy (TAO) before and after glucocorticoid therapy, using voxel-based morphometry (VBM) as well as resting-state functional magnetic resonance imaging (MRI) with amplitude of low-frequency fluctuation (ALFF) and regional homogeneity (ReHo).
METHODS
Between 2019 and 2022, 32 patients with TAO and 23 healthy controls underwent pre-therapy MRI in Nanjing, China. Intravenous glucocorticoid therapy was administered to all patients. At 3 months after end of therapy, 26 patients were available for rescanned MRI. VBM, ALFF, and ReHo were used to evaluate the brain structural and functional differences.
RESULTS
Before therapy, TAO patients showed significantly decreased gray matter volume (GMV) in the left orbital part of superior frontal gyrus (ORBsup) and medial superior frontal gyrus (SFGmed) than healthy controls. Patients had higher ALFF values in bilateral gyrus rectus and olfactory cortex and lower values in bilateral cuneus. Patients also showed decreased ReHo values in bilateral lingual gyrus. After therapy, increased GMV in the left anterior cingulate gyrus and SFGmed, increased ALFF values in bilateral cuneus and superior occipital gyrus, and increased ReHo values in bilateral SFGmed were found in TAO patients compared to the pre-therapy cohort. Compared to controls, decreased GMV in left ORBsup was observed in post-therapy TAO patients.
CONCLUSION
Our results indicated that TAO might cause functional and structural deficits in the visual and emotional regions of the brain, with recovery in the former and partial restoration in the latter after effective glucocorticoid therapy. These findings may lead to deeper understanding of the pathophysiological mechanism behind TAO.
Topics: Humans; Glucocorticoids; Graves Ophthalmopathy; Brain; Gray Matter; Brain Mapping; Magnetic Resonance Imaging
PubMed: 37864850
DOI: 10.1210/clinem/dgad626 -
Frontiers in Aging Neuroscience 2023To determine changes in protein expression related to brain aging and imaging features in mice after chronic hypoxia exposure at high altitude.
OBJECTIVE
To determine changes in protein expression related to brain aging and imaging features in mice after chronic hypoxia exposure at high altitude.
METHOD
A total of 24 healthy 4-week-old mice were randomly divided into high altitude hypoxia (HH) and plain control (PC) groups ( = 8 per group). HH mice were transported from Xi'an (450 m above sea level) to Maduo (4,300 m above sea level) while PC mice were raised in Xi'an. After 6 months, 7.0T magnetic resonance imaging (MRI) was performed. All mice completed T2-weighted imaging (T2WI), diffusion tensor imaging (DTI), resting-state functional MRI (rs-fMRI), arterial spin labeling (ASL), and magnetic resonance angiography (MRA) examinations. Next, brain slices were prepared and Nissl staining was used to observe morphological changes in neurons. Ultrastructural changes in neurons were observed by transmission electron microscopy. Expression changes of Caspase-3, klotho, P16, P21, and P53 at the gene and protein levels were detected by real-time PCR (RT-PCR) and Western blot.
RESULTS
The number of neuronal Nissl bodies in the hippocampus and frontal cortex was significantly decreased in the HH group compared to the PC group. Some hippocampal and frontal cortical neurons were apoptotic, the nuclei were wrinkled, chromatin was aggregated, and most mitochondria were mildly swollen (crista lysis, fracture). Compared with the PC group, the HH group showed elevated expression of caspase-3 mRNA, P16 mRNA, P21 mRNA, and P53 mRNA in the hippocampus and frontal cortex. Expression of Klotho mRNA in the frontal cortex was also significantly decreased. Western blot results showed that caspase-3 protein expression in the hippocampus and frontal cortex of the HH group was increased compared with the PC group. Moreover, there was decreased Klotho protein expression and significantly increased P-P53 protein expression. Compared with the PC group, expression of P16 protein in the frontal cortex of the HH group was increased and the gray matter (GM) volume in the left visceral area, left caudate nucleus, and left piriform cortex was decreased. Furthermore, the amplitude of low frequency fluctuation was decreased in the left posterior nongranular insular lobe, right small cell reticular nucleus, left flocculus, left accessory flocculus, and left primary auditory area, but increased in the GM layer of the left superior colliculus. Regional homogeneity was decreased in the left and right olfactory regions, but increased in the left bed nucleus. After exposure to high altitude, functional connectivity (FC) between the bilateral caudate nucleus and thalamus, corpus callosum, cingulate gyrus, anterior limbic cortex, globus pallidus, and hippocampus was weakened. FC between the right caudate nucleus and hypothalamus and entorhinal cortex was also weakened. The fractional anisotropy value of the left hippocampus was decreased in the HH group. Compared with the PC group, the HH group showed significantly increased inner diameters of the bilateral common carotid artery and left internal carotid artery. The cerebral blood flow values of the bilateral cortex and bilateral hippocampus in the HH group did not change significantly.
CONCLUSION
Taken together, our findings show that chronic hypoxia exposure at high altitude may promote neuronal apoptosis and abnormal expression of related proteins, changing the structure and function of brain. These changes may contribute to brain aging.
PubMed: 37849650
DOI: 10.3389/fnagi.2023.1268230