Low-frequency Fluctuations Research Articles

Dynamic amplitude of low-frequency fluctuation links dark personalities to malevolent creative behavior.

Malevolent creativity refers to the ability to generate ideas that cause harm to oneself or others. While previous research has touched on how personality traits influence malevolent creative behavior, the neural mechanisms involved remain underexplored. This study investigated the brain patterns associated with malevolent creative behavior and how these patterns are mediated by dark personality traits (Machiavellianism, narcissism, and psychopathy) and positive traits (internalization, symbolization, and honesty-humility). Our findings revealed that Machiavellianism mediated the relationship between the amplitude of low-frequency fluctuation (ALFF) in the left medial superior frontal gyrus (mSFG), pallidum (PAL), and middle temporal gyrus (MTG) and malevolent creative behavior, particularly in actions like hurting people or playing tricks. Psychopathy similarly mediated the link between the ALFF in the right orbital middle frontal gyrus (oMFG), right mSFG, left PAL, and left MTG and malevolent creative behavior. Additionally, Machiavellianism negatively mediated the relationship between the fractional ALFF (fALFF) of the left parahippocampal gyrus (PHG) and hurting people, as well as between the fALFF of the left inferior occipital gyrus (IOG) and playing tricks. The ALFF in the left mSFG and left MTG predicted playing tricks but also negatively predicted internalization and honesty-humility, which in turn reduced engagement in playing tricks. Finally, the fALFF of the left IOG negatively predicted playing tricks and positively predicted internalization, which again decreased playing tricks. These findings highlight the complex interaction between brain activity, personality traits, and malevolent creative behavior, offering a potential path for targeted interventions and further research into this interesting phenomenon.

Decreases in frequency-dependent intrinsic activity of the default mode network are associated with depression and cognition in patients with postacute sequelae of SARS-CoV-2 infection.

A significant proportion of patients who have recovered from COVID-19 suffer from persistent symptoms, referred to as "post-acute sequelae of SARS-CoV-2 infection (PASC)". Abnormal brain intrinsic activity has been observed in PASC patients, but the patterns of frequency-dependent intrinsic activity in the PASC and non-PASC (recovered COVID-19 patients without persistent symptoms) groups and their association with neuropsychiatric sequelae remain unclear in PASC. Twenty-nine PASC patients, 27 non-PASC subjects, and 31 healthy controls (HCs) were recruited. The voxel-level fractional amplitude of low-frequency fluctuation (fALFF) was calculated in different frequency bands (typical frequency band: 0.01-0.10Hz; slow 5: 0.01-0.023Hz; slow 4: 0.023-0.073Hz) to assess regional intrinsic activity patterns within different groups. Correlation analyses were performed to explore the associations between frequency-dependent alterations and clinical variables. Significant frequency-dependent alterations in intrinsic activity patterns were observed in both the PASC and non-PASC groups, primarily involving regions of the default mode network (DMN). The decreased fALFF values of the DMN in different frequency bands were associated with different symptoms in PASC. For example, decreased fALFF in the left precuneus in the typical frequency band was related to general attention impairment in PASC, whereas decreased fALFF in the left superior frontal gyrus appeared in non-PASC. The fALFF alterations in the left precuneus/posterior cingulate gyrus in the slow 5 band were also related to cognitive performance in PASC. Additionally, in the slow 4 band, decreased fALFF in the right angular gyrus was associated with depressive symptoms in the PASC. Our results may provide insights into the potential neural mechanisms underlying symptoms in PASC patients.

Obstructive sleep apnea and structural and functional brain alterations: a brain-wide investigation from clinical association to genetic causality

BackgroundObstructive sleep apnea (OSA) is linked to brain alterations, but the specific regions affected and the causal associations between these changes remain unclear.MethodsWe studied 20 pairs of age-, sex-, BMI-, and education- matched OSA patients and healthy controls using multimodal magnetic resonance imaging (MRI) from August 2019 to February 2020. Additionally, large-scale Mendelian randomization analyses were performed using genome-wide association study (GWAS) data on OSA and 3935 brain imaging-derived phenotypes (IDPs), assessed in up to 33,224 individuals between December 2023 and March 2024, to explore potential genetic causality between OSA and alterations in whole brain structure and function.ResultsIn the cohort study, OSA patients exhibited significantly lower fractional amplitude of low-frequency fluctuation and regional homogeneity in the right posterior cerebellar lobe and bilateral superior and middle frontal gyrus, while showing higher levels in the left occipital lobe and left posterior central gyrus. Decreased fractional anisotropy (FA) but increased apparent diffusion coefficient (ADC) was shown in the bilateral superior longitudinal fasciculus. According to the results of Affiliation file 2: table s6, it is the ADC value of right superior longitudinal fasciculus was shown a positive correlation with the lowest oxygen saturation. In the Mendelian randomization analyses, the area of left inferior temporal sulcus (OR: 0.89; 95% CI: 0.82–0.96), rfMRI connectivity ICA100 edge 893 (OR: 0.88; 95% CI: 0.82–0.96), ICA100 edge 951 (OR: 0.89; 95% CI: 0.82–0.97), and ICA100 edge 1213 (OR: 0.89; 95% CI: 0.82–0.96) were significantly decreased in OSA. Conversely, mean thickness of G-front-inf-Triangul in right hemisphere (OR: 1.14; 95% CI: 1.05–1.23), mean orientation dispersion index in right tapetum (OR: 1.13; 95% CI: 1.04–1.23), and rfMRI connectivity ICA100 edge 258 (OR: 1.13; 95% CI: 1.04–1.22) showed opposite results.ConclusionsNerve fiber damage and imbalances in neuronal activity across multiple brain regions caused by hypoxia, particularly the frontal lobe, underlie the structural and the functional connectivity impairments in OSA.

Research on noise-induced hearing loss based on functional and structural MRI using machine learning methods

Noise-induced hearing loss (NIHL) is a common occupational condition. The aim of this study was to develop a classification model for NIHL on the basis of both functional magnetic resonance imaging (fMRI) and structural magnetic resonance imaging (sMRI) by applying machine learning methods. fMRI indices such as the amplitude of low-frequency fluctuation (ALFF), fractional amplitude of low-frequency fluctuation (fALFF), regional homogeneity (ReHo), degree of centrality (DC), and sMRI indices such as gray matter volume (GMV), white matter volume (WMV), and cortical thickness were extracted from each brain region. The least absolute shrinkage and selection operator was used to reduce and select the optimal features. The support vector machine (SVM), random forest (RF) and logistic regression (LR) algorithms, were used to establish the classification model for NIHL. Finally, the SVM model based on combined fMRI indices, achieved the best performance, with area under the receiver operating characteristic curve of 0.97 and an accuracy of 95%. The SVM classification model that integrates fMRI indicators has the greatest potential for identifying NIHL patients and healthy people, revealing the complementary role of fMRI indicators in classification and indicating that it is necessary to include multiple indicators of the brain when establishing a classification model.

Fractional amplitude of low-frequency fluctuations during music-evoked autobiographical memories in neurotypical older adults

IntroductionResearchers have shown that music-evoked autobiographical memories (MEAMs) can stimulate long-term memory mechanisms while requiring little retrieval effort and may therefore be used in promising non-pharmacological interventions to mitigate memory deficits. Despite an increasing number of studies on MEAMs, few researchers have explored how MEAMs are bound in the brain.MethodsIn the current study activation indexed by fractional amplitude of low frequency fluctuations (fALFF) during familiar and unfamiliar MEAM retrieval was compared in a sample of 24 healthy older adults. Additionally, we aimed to investigate the impact of age-related gray matter volume (GMV) reduction in key regions associated with MEAM-related activation. In addition to a T1 structural scan, neuroimaging data were collected while participants listened to familiar music (MEAM retrieval) versus unfamiliar music.ResultsWhen listening to familiar compared to unfamiliar music, greater fALFF activation patterns were observed in the right parahippocampal gyrus, controlling for age and GMV. The current findings for the familiar (MEAM) condition have implications for cognitive aging as persons experiencing age-related memory decline are particularly susceptible to volumetric reduction in the parahippocampal cortex. Post-hoc analyses to explore correlations between brain activity and the content of MEAMs were performed using the text analysis program Linguistic Inquiry and Word Count.DiscussionOur findings suggest that MEAM-related activation of the parahippocampal cortex is evident in normative older adults. However, it is yet to be determined whether such brain states are attainable in older adult populations diagnosed with mild cognitive impairment and/or prodromal Alzheimer’s disease.

Bridging animal models and humans: neuroimaging as intermediate phenotypes linking genetic or stress factors to anhedonia

BackgroundIntermediate phenotypes, such as characteristic neuroimaging patterns, offer unique insights into the genetic and stress-related underpinnings of neuropsychiatric disorders like depression. This study aimed to identify neuroimaging intermediate phenotypes associated with depression, bridging etiological factors to behavioral manifestations and connecting insights from animal models to diverse clinical populations.MethodsWe analyzed datasets from both rodents and humans. The rodent studies included a genetic model (P11 knockout) and an environmental stress model (chronic unpredictable mild stress), while the human data comprised 748 participants from three cohorts. Using the amplitude of low-frequency fluctuations, we identified neuroimaging patterns in rodent models. We then applied a machine-learning approach to cluster neuroimaging subtypes of depression. To assess the genetic predispositions and stress-related changes associated with these subtypes, we analyzed genotype and metabolite data. Linear regression was employed to determine which neuroimaging features predicted core depression symptoms across species.ResultsThe genetic and environmental stress models exhibited distinct neuroimaging patterns in subcortical and sensorimotor regions. Consistent patterns emerged in two neuroimaging subtypes identified across three independent depressed cohorts. The subtype resembling P11 knockout demonstrated higher genetic susceptibility, with enriched expression of risk genes in brain tissues and abnormal metabolites linked to tryptophan metabolism. In contrast, the stress animal-like subtype did not show changes in genetic risk scores but exhibited enriched risk gene expression in somatic and endocrine tissues, along with mitochondrial dysfunction in the antioxidant stress system. Notably, these distinct subcortical-sensorimotor neuroimaging patterns predicted anhedonia, a core symptom of depression, in both rodent models and depressed subtypes.ConclusionsThis cross-species validation suggests that these neuroimaging patterns may serve as robust intermediate phenotypes, linking etiology to anhedonia and facilitating the translation of findings from animal models to humans with depression and other psychiatric disorders.

Experimental identification of I-mode characteristics at the edge of FIRE mode in KSTAR

Abstract The edge region of the recently discovered fast ion-regulated enhancement mode (FIRE mode) (Han and Park et al. 2022 Nature 609 269-275), which primarily operates in the unfavorable ion ∇B drift configuration, is investigated in detail. An ion temperature pedestal is identified, while the edge electron density profile remains at low-confinement mode (L-mode) level, displaying characteristics of the edge profiles in improved energy confinement mode (I-mode). The weakly coherent mode (WCM) is observed at around 50 kHz in the spectrum of edge electron density fluctuations measured by beam emission spectroscopy. The weakly coherent feature becomes more pronounced as the amplitude of intermediate-frequency fluctuations (approximately 10--30 kHz) decreases, coinciding with a rise in the height of the temperature pedestal. The WCM propagates in the ion diamagnetic drift direction in the laboratory frame, but its propagation direction in the E × B flow frame has yet to be determined. Nonlinear phase coupling between the low-frequency density fluctuation components and the WCMs is identified, indicating the presence of zonal density. This coupling typically occurs as the H-mode transition approaches, and its potential link to a regulatory process is discussed. When the coupling manifests, intermittent bursts are observed concurrently, not just at the radial location where the WCM amplitude peaks, but throughout the edge region. No other coherent oscillations with finite frequency have been detected thus far.

The amplitude of low frequency fluctuation and spontaneous brain activity alterations in age-related macular degeneration

BackgroundWet age-related macular degeneration (wAMD) is a vision-threatening eye disease worldwide. The amplitude of low-frequency fluctuation (ALFF) method was used to observe changes in spontaneous brain activity, which may help to investigate the underlying pathological mechanism of AMD.MethodsEighteen patients with wAMD and 18 age- and gender-matched healthy controls (HCs) were recruited. The ALFF method was used on each subject and mean ALFF values were compared between groups. The receiver operating characteristic (ROC) curve was used to compare the two groups.ResultsALFF values in the temporal lobe and limbic lobe/parahippocampal gyrus were significantly higher than controls, while values in the postcentral gyrus were significantly lower. The under the curve of the ROC (AUC) of the three regions shows high accuracy of the diagnosis.ConclusionThe abnormal spontaneous brain activity of patients with AMD suggests scope for the use of ALFF in the diagnosis or prognosis in AMD.

Functional MRI study of neurovascular coupling in patients with non-lesional epilepsy

ObjectiveThe diagnosis of patients with non-lesional epilepsy (NLE) is relatively challenging because of the absence of a clear focus on imaging, and the underlying pathological mechanism remains unclear. The neuronal activity and functional connectivity of NLE patients are significantly abnormal, and the neuronal activity of epilepsy patients is closely related to cerebral blood flow (CBF). Neurovascular coupling (NVC) offers insights into the relationship between neuronal activity and CBF. Hence, we intend to explore the alterations of NVC in NLE patients and their influences on cognitive function.MethodsClinical data of 24 patients with NLE (15 female; age range 19–40 years; median age 30.5 years) and 39 healthy controls (27 female; age range 19–40 years; median age 30 years) were collected, and resting-state functional magnetic resonance imaging (rs-fMRI) and 3D arterial spin labeling (ASL) were performed. The imaging indexes of amplitude of low-frequency fluctuation (ALFF) and CBF were calculated, respectively, by post-processing analysis. The differences in CBF, ALFF and CBF/ALFF ratio between the two groups were analyzed, along with correlation with clinical data of NLE patients.ResultsCompared with the healthy controls, the CBF of the right parahippocampal gyrus was significantly decreased, and the CBF/ALFF ratio of the right inferior parietal, but supramarginal and angular gyri was significantly increased in NLE patients (p < 0.001). Moreover, the CBF/ALFF ratio was positively correlated with epilepsy depression score (r = 0.546, p = 0.006).ConclusionNLE patients showed abnormal local NVC, which was associated with the severity of depression. The combined application of rs-fMRI and ASL can comprehensively evaluate the neuronal activity and cerebral blood perfusion in patients with NLE. The abnormal NVC is of great significance for us to explore the central mechanism of the occurrence and development of NLE.

Dynamic Neural Mechanisms Underlying Sustained Motor Training Post-Stroke: An fNIRS Investigation Employing Time-Varying ALFF and Functional Connectivity Analysis.

Motor dysfunction of the upper limbs following a stroke predominantly arises from abnormal motor patterning caused by the disrupted balance of inter-cortical communication within motor-associated cortical regions. Temporal analysis offers a more precise reflection of the cortical functional state in affected patients. This study employed fNIRS to capture hemodynamic responses among 20 stroke patients and 19 healthy controls in both resting and Baduanjin task state. Including computing the coefficient of variation of fractional amplitude of low-frequency fluctuations (fALFF) for each channel, alongside extracting dynamic state metrics. Findings indicate that, during sustained motor tasks, stroke patients exhibit a diminished fALFF variability in targeted cortical regions; these individuals display a higher prevalence of low-intensity states and a lower prevalence of high-intensity states during task execution. These dynamic state attributes are significantly associated with scores on the upper limb motor function scale (FMA-UE), thereby proposing a time-domain perspective for investigating the underlying mechanisms of stroke-induced motor dysfunction.

Low-Frequency Resistance Noise in Near-Magic-Angle Twisted Bilayer Graphene.

The low-frequency resistance fluctuations, or noise, in electrical resistance not only set a performance benchmark in devices but also form a sensitive tool to probe nontrivial electronic phases and band structures in solids. Here, we report the measurement of such noise in the electrical resistance in twisted bilayer graphene (tBLG), where the layers are misoriented close to the magic angle (θ ∼ 1°). At high temperatures (T ≳ 60-70 K), the power spectral density (PSD) of the fluctuation inside the low-energy moiré bands is predominantly ∝1/f, where f is the frequency, being generally lowest close to the magic angle, and can be well-explained within the conventional McWhorter model of the '1/f noise' with trap-assisted density-mobility fluctuations. At low T (≲10 K), the measured noise exhibits a strong two-level random telegraphic signal (RTS), especially close to the moiré gap, which exhibits a ∝1/f2-like PSD that can be attributed to poorly screened resonances of the Fermi energy to specific bands of defects in the encapsulating boron nitride (hBN) layers. The low-T noise within the moiré band exhibits a series of minima at the integral as well as half-integral fillings, which align with the frequently observed van Hove singularities in the density-of-states driven by strong Coulomb interaction. Apart from providing a comprehensive account of the origin and the magnitude of noise in tBLG, our experiment also reveals noise to be significantly more sensitive to the underlying interaction effects in tBLG than the conventional time-averaged transport.

Neurovascular coupling dysfunction associated with inflammatory factors in sudden sensorineural hearing loss.

The neuropathologic mechanisms of sudden sensorineural hearing loss (SSNHL) are unknown. The aim of this study was to investigate the alterations of neurovascular coupling (NVC) in patients with SSNHL and its association with hematologic inflammatory factors. The amplitude of low-frequency fluctuations (ALFF), fractional amplitude of low-frequency fluctuations (fALFF), regional homogeneity (ReHo), and degree centrality (DC) were calculated in 48 patients with SSNHL and 54 age-, gender-, and education-matched healthy control (HC), and also utilized the arterial spin labeling imaging (ASL) to calculate cerebral blood flow (CBF). Four indices of NVC (CBF-ALFF, CBF-fALFF, CBF-ReHo, and CBF-DC) in the whole brain gray matter as well as the NVC ratio were compared between two groups. In addition, correlation analyses were performed with inflammatory factors for the NVC indexes at the global level and regional level, respectively. The NVC at global level was lower in SSNHL group than in HC, except for CBF-ALFF. At the regional level, most of the brain regions with abnormal NVC in SSNHL patients involved auditory and sensorimotor language centers and limbic system compared to HC. In addition, both at the global and regional levels, NVC metrics were shown to correlate with partial inflammatory factors or hematologic parameters, including platelet-lymphocyte ratio (PLR), neutrophil-lymphocyte ratio (NLR), systemic immunoinflammatory index (SII), blood platelet count (PLT), and lymphocyte count (Lym). From the view of the NVC metrics, these findings provide new perspectives on the neuropathologic mechanisms and clinical treatment of SSNHL.

Exploring the link between inflammation and brain function after metabolic-bariatric surgery: A year-long fMRI study.

Metabolic-bariatric surgery (MBS) transcends weight loss and offers wide-ranging health benefits, including positive effects on brain function. However, the mechanisms behind these effects remain unclear, particularly in the context of significant postoperative changes in the inflammatory profile characteristic of MBS. Understanding how inflammation influences postoperative brain function can enhance our decision-making on patient eligibility for MBS and create new opportunities to improve the outcomes of this popular treatment. To identify brain regions where spontaneous neural activity and functional connectivity are linked with the evolving inflammatory profile following MBS. We investigated the relationship between the perioperative ratio of interleukin (IL)-6 to IL-10 and both the amplitude of low-frequency fluctuation (ALFF) and functional connectivity across 375 brain regions. We examined 36 patients at three time points: 1 week before, and 3 and 12 months after laparoscopic sleeve gastrectomy. Initially, the IL-6/IL-10 ratio increased during the early postoperative period but then decreased to levels lower than the preoperative values 1 year after surgery. We observed that ALFF in four subcortical structures decreased with a rising IL-6/IL-10 ratio and increased with a declining ratio. Conversely, 16 cortical regions displayed the opposite trend. Additionally, functional connectivity between the left insula and bilateral medial prefrontal cortex increased with a rising IL-6/IL-10 ratio and decreased with a declining ratio. Our study is the first to identify brain regions significantly linked to inflammation after MBS. Importantly, many of the discovered areas were previously shown to be involved in the pathogenesis of obesity or are targets of contemporary medical treatments. Consequently, our findings offer valuable insights for future obesity research, especially in the context of potential therapeutic opportunities.

Disease-State Dependent Associations Between Intrinsic Brain Function and Symptoms of Fatigue, Depression, and Anxiety in Crohn's Disease.

Extraintestinal symptoms (EIS) in inflammatory bowel diseases, including fatigue, depression and anxiety, are highly prevalent, but poorly understood. Alterations of brain function may contribute to EIS, but their association with disease activity is unclear. This study analyzed intrinsic neural activity (INA) of individuals with Crohn's disease (CD) in different disease states and examined the relationship between INA and EIS. Patients with CD (n = 92) and healthy controls (n = 41) underwent functional magnetic resonance brain imaging and completed symptom-specific psychometry. Temporal (amplitude of low-frequency fluctuations, ALFF) and spatial (regional homogeneity, ReHo) markers of INA were compared between CD and controls and between active (patients with active Crohn's disease [aCD]) versus remitted (rCD) disease. Regression analyses explored disease-state-dependent associations between INA and EIS. Patients exhibited aberrant INA in frontotemporal, occipital, and thalamic regions. Patients with aCD exhibited lower ALFF in left subcallosal cortex and inferior temporal gyri compared to rCD. Regional homogeneity in aCD was lower in left medial orbital gyrus and higher in right superior frontal, left inferior temporal, and left precentral gyrus. Compared to rCD, aCD showed higher ALFF predominantly in superior, ventro-, and dorsolateral prefrontal regions. Distinct associations between INA and EIS were detected in patients, particularly in the remitted state. Intrinsic brain function in patients with CD varies by disease state, with prominent frontal cortex changes in active disease. These brain activity changes are at least partly related to the magnitude of neuropsychiatric symptoms and highlight a role of disturbed brain-gut interactions in the development of EIS especially in rCD.

Altered spontaneous brain activity in children with deprivation amblyopia: a resting-state functional magnetic resonance imaging study

BackgroundTo investigate the alterations in spontaneous brain activity and the similarities and differences between monocular deprivation amblyopia and binocular deprivation amblyopia.MethodsTwenty children with binocular deprivation amblyopia, 26 children with monocular deprivation amblyopia and 20 healthy controls underwent resting-state functional magnetic resonance imaging. The evaluation of altered spontaneous brain activity was conducted using fractional amplitude of low-frequency fluctuations (fALFF). One-way analysis of variance was employed to analyze fALFF values among the three groups. Additionally, the relationship between fALFF values and best corrected visual acuity (BCVA) was analyzed via correlation analysis.ResultsCompared to healthy controls, children with binocular deprivation amblyopia presented increased fALFF values in the left medial superior frontal gyrus, left middle frontal gyrus, left anterior cingulate cortex, left postcentral gyrus and bilateral precentral gyrus, and decreased fALFF values in the right fusiform gyrus. Compared to healthy controls, children with monocular deprivation amblyopia presented increased fALFF values in the right lingual gyrus, right superior frontal gyrus, right middle frontal gyrus, left superior temporal gyrus, triangular part of the left inferior frontal gyrus and bilateral middle temporal gyrus, and decreased fALFF values in the right precuneus. Compared with monocular deprivation amblyopia, fALFF values of binocular deprivation amblyopia were decreased in the triangular part of the left inferior frontal gyrus, right lingual gyrus and right cuneus, and increased in the left precentral gyrus and left postcentral gyrus. No significant correlations were found between the fALFF values of identified regions and the BCVA of amblyopic eyes for either type of amblyopia.ConclusionsChildren with deprivation amblyopia presented alterations in spontaneous activity in multiple brain regions, and these alterations differed between monocular amblyopia and binocular amblyopia. These abnormal spontaneous activities may reflect dysfunctions and compensation related to amblyopia.

Differentiation between multiple sclerosis and neuromyelitis optic spectrum disorders with multilevel fMRI features: A machine learning analysis

The conventional statistical approach for analyzing resting state functional MRI (rs-fMRI) data struggles to accurately distinguish between patients with multiple sclerosis (MS) and those with neuromyelitis optic spectrum disorders (NMOSD), highlighting the need for improved diagnostic efficacy. In this study, multilevel functional metrics including resting state functional connectivity, amplitude of low frequency fluctuation (ALFF), and regional homogeneity (ReHo) were calculated and extracted from 116 regions of interest in the anatomical automatic labeling atlas. Subsequently, classifiers were developed using different combinations of these selected features to distinguish between MS and NMOSD. Compared to models based on individual MRI features, support vector machine (SVM) and logistic regression (LR) models that integrated multilevel functional features such as RSFC, ALFF, and ReHo demonstrated the highest levels of performance on the testing cohorts (SVM, AUC = 0.857; LR, AUC = 0.929). Adding structural features of gray matter volume (GMV) data did not notably improve the classification performance of the machine learning models using multilevel rs-fMRI features. Notably, similar trends were observed across different brain templates, with models based on RSFC, ALFF, and ReHo yielding optimal performance. These findings suggest that utilizing multilevel fMRI features can effectively differentiate between MS and NMOSD patients.

Altered amplitude of low-frequency fluctuation and functional connectivity in patients with acute unilateral vestibulopathy: a resting-state fMRI study.

To investigate changes of brain functional activity in patients with acute unilateral vestibulopathy (AUVP) using functional magnetic resonance imaging (fMRI). We studied 32 AUVP patients and 30 healthy controls (HC) who received resting-state fMRI scanning. Methods of voxel-based amplitude of low-frequency fluctuation (ALFF) and seed-based functional connectivity (FC) were adopted to compare the difference in brain function between the two groups. In addition, we evaluated the associations between abnormal neuroimaging results and clinical data in AUVP patients. Compared with HC, patients with AUVP showed lower ALFF in brain regions of bilateral insular, right precentral gyrus, left inferior frontal gyrus and right middle frontal gyrus, as well as higher ALFF in left cerebellar anterior lobe. Using these abnormal brain areas as seeds, we observed decreased FC between left insular and left precuneus in AUVP patients. Furthermore, AUVP patients showed increased FC between left insular and left supplementary motor area. Results of correlation analysis indicated that ALFF value (z-value) in left insular was negatively correlated with the canal paresis value (p = 0.005, r = -0.483), and the FC (z-value) between left insular and left precuneus was negatively correlated with dizziness handicap inventory score (p = 0.012, r = -0.438) in patients with AUVP. Patients with AUVP during acute period showed altered functional activity and connectivity in brain regions mainly involved in motor control and vestibular information processing. These changes in brain functional activity and connectivity were potentially attributed to decreased vestibular input resulting from unilateral peripheral vestibular impairment.

Distinction in the function and microstructure of white matter between major depressive disorder and generalized anxiety disorder.

Major depressive disorder (MDD) and generalized anxiety disorder (GAD) are two of the leading causes of impairment to human mental health. These two psychiatric disorders overlap in many symptoms and neurobiological features thus difficult to distinguish in some cases. We enrolled 102 participants, comprising 40 patients with MDD, 32 patients with GAD and 30 matched healthy controls (HCs), to undergo multimodal magnetic resonance imaging (MRI) scans. We identified 18 major white matter (WM) tracts with automated fiber quantification (AFQ) method, to evaluated microstructure with fractional anisotropy (FA) and function with amplitude of low-frequency fluctuation (ALFF). An analysis of variance (ANOVA) was employed to identify differences among groups. We further explored the correlations of FA and ALFF features with clinical symptoms. We identified the white matter microstructure and function of 89 participants. ANOVA and post-hoc analysis revealed that GAD group exhibited significantly higher FA of right anterior thalamic radiation (ATR) than in MDD and HC groups. Additionally, MDD group exhibited significantly decreased ALFF in forceps major (FMA), forceps minor (FMI), bilateral corticospinal tracts (CST) and left inferior fronto-occipital fasciculus (IFOF) compared to both GAD and HC group. ALFF of right CST was significantly negatively correlated to HAMA and a moderate effect size and marginal significance was found between FA of the right ATR and HAMA in GAD group. This study used cross-sectional data and sample size was small. Tracking microstructure and function of WM with AFQ method has the potential to distinguish different psychiatric diseases.

Aberrant regional neural fluctuations and functional connectivity in insomnia comorbid depression revealed by resting-state functional magnetic resonance imaging.

Insomnia is a common mental illness seriously affecting people lives, that might progress to major depression. However, the neural mechanism of patients with CID comorbid MDD remain unclear. Combining fractional amplitude of low-frequency fluctuation (fALFF) and seed-based functional connectivity (FC), this study investigated abnormality in local and long-range neural activity of patients with CID comorbid MDD. Here, we acquired resting-state blood oxygenation level dependent (BOLD) data from 57 patients with CID comorbid MDD and 57 healthy controls (HC). Compared with the controls, patients with CID comorbid MDD exhibited abnormal functional activity in posterior cerebral cortex related to the visual cortex, including the middle occipital gyrus (MOG), the cuneus and the lingual gyrus, specifically, lower fALFF values in the right MOG, left cuneus, and right postcentral gyrus, increased FC between the right MOG and the left cerebellum, and decreased FC between the right MOG and the right lingual gyrus. Neuropsychological correlation analysis revealed that the decreased fALFF in the right MOG was negatively correlated with all the neuropsychological scores of insomnia and depression, reflecting common relationships with symptoms of CID and MDD. While the decreased fALFF of the left cuneus was distinctly correlated with the scores of depression related scales. The decreased FC between the right MOG and the right lingual gyrus was distinctly correlated with the scores of insomnia related scales. This study not only widened neuroimaging evidence that associated with insomnia and depressive symptoms of patients with CID comorbid MDD, but also provided new potential targets for clinical treatment.

Research on flow characteristics of discharge pipe during reverse operation of bidirectional axial flow pump

Bidirectional axial flow pumps are of growing importance in flood control and irrigation. Reverse operation is a common concern during the operation of bidirectional pumps. Therefore, this paper focuses on studying the flow state in the discharge pipe of a bidirectional pump operating in reverse at various flow rates, utilizing model testing and numerical simulation methods. Research shows that the spiral flow in the discharge pipe leads to the high head measurements. Moreover, reverse operation generates vortices in the discharge pipe, with greater vortex intensity and range occurring at lower flow rates, causing poor velocity distribution uniformity. The concentration of vortex kinetic energy and energy loss in the discharge pipe is primarily within a range of twice the impeller diameter. Furthermore, as the flow rate decreases, the pressure pulsation in the discharge pipe becomes unstable. At design and large flow rates, the pressure pulsations are mainly due to impeller rotation; however, running at a small flow rate results in low-frequency fluctuations in the discharge pipe, occurring at a cycle time 3.5 times the rotation frequency. This research holds both theoretical and practical significance for enhancing the operational stability and efficiency of bidirectional axial flow pumps.