Low-Frequency Fluctuations Amplitude Signals Exhibit Abnormalities of Intrinsic Brain Activities and Reflect Cognitive Impairment in Leukoaraiosis Patients

Dynamic alterations in the amplitude of low-frequency fluctuation in patients with cerebral small vessel disease

Background and purpose

Previous studies have focused on the changes of dynamic and static functional connections in cerebral small vessel disease (CSVD). However, the dynamic characteristics of local brain activity are poorly understood. The purpose of this study was to investigate the dynamic cerebral activity changes in patients with CSVD using the dynamic amplitude of low-frequency fluctuation (d-ALFF).

Methods

A total of 104 CSVD patients with cognitive impairment (CSVD-CI, n = 52) or normal cognition (CSVD-NC, n = 52) and 63 matched healthy controls (HCs) were included in this study. Every participant underwent magnetic resonance imaging scans and a battery of neuropsychological examinations. The dynamics of spontaneous brain activity were assessed using dynamic changes in the amplitude of low-frequency fluctuation (ALFF) with the sliding-window method. We used voxel-wise one-way analysis of variance (ANOVA) to compare dynamic ALFF variability among the three groups. Post-hoc t-tests were used to evaluate differences between each group pair. Finally, the brain regions with d-ALFF values with differences between CSVD subgroups were taken as regions of interest (ROI), and the d-ALFF values corresponding to the ROI were extracted for partial correlation analysis with memory.

Results

(1) There was no significant difference in age (p = 0.120), sex (p = 0.673) and education (p = 0.067) among CSVD-CI, CSVD-NC and HC groups, but there were significant differences Prevalence of hypertension and diabetes mellitus among the three groups (p < 10-3). There were significant differences in scores of several neuropsychological scales among the three groups (p < 10-3). (2) ANOVA and post-hoc t-test showed that there were dynamic abnormalities of spontaneous activity in several brain regions in three groups, mainly located in bilateral parahippocampal gyrus and bilateral hippocampus, bilateral insular and frontal lobes, and the static activity abnormalities in bilateral parahippocampal gyrus and bilateral hippocampal regions were observed at the same time, suggesting that bilateral parahippocampal gyrus and bilateral hippocampus may be the key brain regions for cognitive impairment caused by CSVD. (3) The correlation showed that d-ALFF in the bilateral insular was slightly correlated with the Mini-Mental State Examination (MMSE) score and disease progression rate. The d-ALFF value of the left postcentral gyrus was negatively correlated with the Clock Drawing Test (CDT) score (r = -0.416, p = 0.004), and the d-ALFF value of the right postcentral gyrus was negatively correlated with the Rey's Auditory Verbal Learning Test (RAVLT) word recognition (r = -0.320, p = 0.028).

Conclusion

There is a wide range of dynamic abnormalities of spontaneous brain activity in patients with CSVD, in which the abnormalities of this activity in specific brain regions are related to memory and execution or emotion.

A mini-review on functional magnetic resonance imaging on brain structure of vascular cognitive impairment

Vascular cognitive impairment (VCI) is the initial stage of vascular dementia (VaD). Early diagnosis and treatment of VCI are crucial to prevent the progression of VaD. In order to gain a better understanding of VCI, this study aimed to investigate the use of advanced imaging techniques such as structural magnetic resonance imaging (sMRI) and resting-state functional magnetic resonance imaging (rs-fMRI). These techniques allow researchers to observe the structural and functional changes in the brain that are associated with VCI. Functional magnetic resonance imaging (fMRI) and sMRI techniques have been widely used in studies focusing on gray matter, brain networks, and functional abnormalities during rest. By searching and summarizing recent literature, this study has provided valuable evidence on the use of advanced imaging techniques in understanding and treating VCI. The findings from this study can aid in the development of early intervention strategies for patients with VCI, potentially slowing down or even halting the progression of VCI to full-blown VaD.

Low-frequency oscillations in the brain show differential regional associations with severity of cerebral small vessel disease: a systematic review

Background

Cerebral small vessel disease (cSVD) is associated with endothelial dysfunction but the pathophysiology is poorly understood. Low-frequency oscillations (LFOs) in the BOLD signal partly reflect cerebrovascular function and have the potential to identify endothelial dysfunction in cSVD. A systematic review was performed to assess the reported relationships between imaging markers of cSVD and LFOs.

Methods

Medline and EMBASE were searched for original studies reporting an association between LFOs and STRIVE-defined imaging markers of cSVD, including: white matter hyperintensities (WMH), enlarged perivascular spaces, lacunes, CADASIL, and cerebral microbleeds, from inception to September 1, 2022. Variations in LFOs were extracted, where available, on a global, tissue-specific, or regional level, in addition to participant demographics, data acquisition, methods of analysis, and study quality. Where a formal meta-analysis was not possible, differences in the number of studies reporting LFO magnitude by presence or severity of cSVD were determined by sign test.

Results

15 studies were included from 841 titles. Studies varied in quality, acquisition parameters, and in method of analysis. Amplitude of low-frequency fluctuation (ALFF) in resting state fMRI was most commonly assessed (12 studies). Across 15 studies with differing markers of cSVD (9 with WMH; 1 with cerebral microbleeds; 1 with lacunar infarcts; 1 with CADASIL; 3 with multiple markers), LFOs in patients with cSVD were decreased in the posterior cortex (22 of 32 occurrences across all studies, p = 0.05), increased in the deep grey nuclei (7 of 7 occurrences across all studies, p = 0.016), and potentially increased in the temporal lobes (9 of 11 occurrences across all studies, p = 0.065).

Conclusion

Despite limited consensus on the optimal acquisition and analysis methods, there was reasonably consistent regional variation in LFO magnitude by severity of cSVD markers, supporting its potential as a novel index of endothelial dysfunction. We propose a consistent approach to measuring LFOs to characterise targetable mechanisms underlying cSVD.

Frequency specificity in the amplitude of low frequency oscillations in patients with white matter lesions

Previous studies have reported that patients with white matter lesions (WMLs) have abnormal spontaneous brain activity in the resting state. However, the spontaneous neuronal activity of specific frequency bands in WMLs patients is unknown. Here, we included 16 WMLs patients and 13 gender and age-matched healthy controls (HCs) underwent resting-state magnetic resonance imaging (rs-fMRI) scan and studied the specificity of the amplitude of low-frequency fluctuations (ALFF) in WMLs patients in the slow-5 (0.01-0.027 Hz), slow-4 (0.027-0.073 Hz), and typical (0.01-0.08 Hz) frequency bands. In addition, ALFF values of different frequency bands were extracted as classification features and support vector machines (SVM) were used to classify WMLs patients. In all three frequency bands, significant increases in ALFF values in WMLs patients were observed in the cerebellum. In the slow-5 band, the ALFF values of the left anterior cingulate and paracingulate gyri (ACG), and the right precentral gyrus, rolandic operculum and inferior temporal gyrus in WMLs patients were lower than those in HCs. In the slow-4 band, ALFF values were lower in WMLs patients than in HCs at the left ACG, the right median cingulate and paracingulate gyri, parahippocampal gyrus, caudate nucleus, and the bilateral lenticular nucleus, putamen. In the SVM classification model, the classification accuracy of slow-5, slow-4 and typical frequency bands is 75.86%, 86.21% and 72.41%, respectively. The results indicate that the ALFF abnormalities in WMLs patients have frequency specificity, and the ALFF abnormalities in the slow-4 frequency band may serve as imaging markers for WMLs.

Multimodality neuroimaging in vascular mild cognitive impairment: A narrative review of current evidence

The vascular mild cognitive impairment (VaMCI) is generally accepted as the premonition stage of vascular dementia (VaD). However, most studies are focused mainly on VaD as a diagnosis in patients, thus neglecting the VaMCI stage. VaMCI stage, though, is easily diagnosed by vascular injuries and represents a high-risk period for the future decline of patients' cognitive functions. The existing studies in China and abroad have found that magnetic resonance imaging technology can provide imaging markers related to the occurrence and development of VaMCI, which is an important tool for detecting the changes in microstructure and function of VaMCI patients. Nevertheless, most of the existing studies evaluate the information of a single modal image. Due to the different imaging principles, the data provided by a single modal image are limited. In contrast, multi-modal magnetic resonance imaging research can provide multiple comprehensive data such as tissue anatomy and function. Here, a narrative review of published articles on multimodality neuroimaging in VaMCI diagnosis was conducted，and the utilization of certain neuroimaging bio-markers in clinical applications was narrated. These markers include evaluation of vascular dysfunction before tissue damages and quantification of the extent of network connectivity disruption. We further provide recommendations for early detection, progress, prompt treatment response of VaMCI, as well as optimization of the personalized treatment plan.

Disconnection of Network Hubs Underlying the Executive Function Deficit in Patients with Ischemic Leukoaraiosis

BACKGROUND

Cognitive impairment is the most common clinical manifestation of ischemic leukoaraiosis (ILA), but the underlying neurobiological pathways have not been well elucidated. Recently, it was thought that ILA is a "disconnection syndrome". Disorganized brain connectome were considered the key neuropathology underlying cognitive deficits in ILA patients.

OBJECTIVE

We aimed to detect the disruption of network hubs in ILA patients using a new analytical method called voxel-based eigenvector centrality (EC) mapping.

METHODS

Subjects with moderate to severe white matters hyperintensities (Fazekas score ≥3) and healthy controls (HCs) (Fazekas score = 0) were included in the study. The resting-state functional magnetic resonance imaging and the EC mapping approach were performed to explore the alteration of whole-brain network connectivity in ILA patients.

RESULTS

Relative to the HCs, the ILA patients exhibited poorer cognitive performance in episodic memory, information processing speed, and executive function (all ps < 0.0125). Additionally, compared with HCs, the ILA patients had lower functional connectivity (i.e., EC values) in the medial parts of default-mode network (i.e., bilateral posterior cingulate gyrus and ventral medial prefrontal cortex [vMPFC]). Intriguingly, the functional connectivity strength at the right vMPFC was positively correlated with executive function deficit in the ILA patients.

CONCLUSION

The findings suggested disorganization of the hierarchy of the default-mode regions within the whole-brain network in patients with ILA and advanced our understanding of the neurobiological mechanism underlying executive function deficit in ILA.

Structural and functional alterations in cerebral small vessel disease: an ALE-based meta-analysis

 

Cerebral small vessel disease (CSVD) is one of the most important causes of stroke and dementia. Although increasing studies have reported alterations of brain structural or neuronal functional activity exhibited in patients with CSVD, it is still unclear which alterations are reliable. Here, we performed a meta-analysis to establish which brain structural or neuronal functional activity changes in those studies were consistent. Activation likelihood estimation revealed that changes in neuronal functional activity in the left angular gyrus, bilateral anterior cingulate cortex/left medial prefrontal cortex, right rolandic operculum, and alterations of gray structure in the left insular cortex/superior temporal gyrus/claustrum were reliable in sporadic CSVD. Decreased neuronal functional activity in the caudate head, anterior cingulate cortex, and reduced gray matter volume in the insular cortex/superior temporal gyrus/claustrum were associated with CSVD-related cognitive impairment. Furthermore, unlike sporadic CSVD, the reliable alterations of neuronal functional activity in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy were concentrated in the left parahippocampal gyrus. The current study presents stable brain structural and neuronal functional abnormalities within the brain, which can help further understand the pathogenesis of CSVD and CSVD-cognitive impairment and provide an index to evaluate the effectiveness of treatment protocols.

Highlights

• Default mode network and salience network are reliable networks affected in sporadic CSVD in resting-state.

• Altered corticostriatal circuitry is associated with cognitive decline.

• Decreased gray matter volume in the insular cortex is stable “remote effects” of sporadic CSVD.

• The parahippocampal gyrus may be a reliable affected brain region in CADASIL.

Brain microstructural alterations in the left precuneus mediate the association between KIBRA polymorphism and working memory in healthy adults: a diffusion kurtosis imaging study

Kidney and brain expressed protein (KIBRA) rs17070145 is associated with working memory function and cognitive processes. However, the neural mechanisms underlying these associations are not fully understood. This study aimed to explore the effect of KIBRA polymorphism on brain microstructure and blood oxygenation level dependent (BOLD) fluctuations using diffusion kurtosis imaging (DKI) and resting-state functional magnetic resonance imaging (fMRI) in 163 young adults. We also investigated that whether the imaging alterations mediated the association between KIBRA gene and working memory performance. Voxel-based analysis of DKI data showed that KIBRA C-allele carriers exhibited increased axial diffusivity (AD), radial diffusivity (RD) and mean diffusivity (MD) as well as decreased fractional anisotropy (FA), mean kurtosis (MK) and radial kurtosis (RK) compared with KIBRA TT homozygotes, primarily involving the prefrontal lobe, left precuneus and the left superior parietal white matter. Meanwhile, KIBRA C-allele carriers exhibited decreased amplitude of low-frequency fluctuation (ALFF) in the left precuneus compared to KIBRA TT homozygotes. Mediation analysis revealed that the DKI metrics (MK and RK) of the left precuneus mediated the effect of the KIBRA polymorphism on working memory performance. Moreover, the MK and RK in the left precuneus were positively correlated with ALFF in the same brain region. These findings suggest that abnormal DKI parameters may provide a gene-brain-behavior pathway in which KIBRA rs17070145 affects working memory by modulating brain microstructure in the left precuneus. This illustrates that DKI may provide additional biological information and reveal new insights into the neural mechanisms of the KIBRA polymorphism.

Research Progress on MRI for White Matter Hyperintensity of Presumed Vascular Origin and Cognitive Impairment

White matter hyperintensity of presumed vascular origin (WMH) is a common medical imaging manifestation in the brains of middle-aged and elderly individuals. WMH can lead to cognitive decline and an increased risk of cognitive impairment and dementia. However, the pathogenesis of cognitive impairment in patients with WMH remains unclear. WMH increases the risk of cognitive impairment, the nature and severity of which depend on lesion volume and location and the patient's cognitive reserve. Abnormal changes in microstructure, cerebral blood flow, metabolites, and resting brain function are observed in patients with WMH with cognitive impairment. Magnetic resonance imaging (MRI) is an indispensable tool for detecting WMH, and novel MRI techniques have emerged as the key approaches for exploring WMH and cognitive impairment. This article provides an overview of the association between WMH and cognitive impairment and the application of dynamic contrast-enhanced MRI, structural MRI, diffusion tensor imaging, 3D-arterial spin labeling, intravoxel incoherent motion, magnetic resonance spectroscopy, and resting-state functional MRI for examining WMH and cognitive impairment.

A Functional Magnetic Resonance Imaging Study on Activation of Anterior Cingulate Cortex at Episode and Interictal Phases in Migraine

<sec> <title>Objective:</title> By using amplitude of low-frequency fluctuations (ALFF) we have analyzed activationsin brain regions at different phases in migraineurs. </sec> <sec> <title>Methods:</title> Participants included 41 patients with migraine, 19 in episode and 22 in interictal phase, and 22 controls in the healthy condition. To analyze the brain function of patients and controls, ALFF was used for performing the post-processing in the resting state by scores of Montreal Cognitive Assessment (MoCA) scale, Mini-Mental State Examination (MMSE), Hamilton Anxiety Rating Scale (HAM-A) and Hamilton Depression Rating Scale (HAM-D). </sec> <sec> <title>Results:</title> The comparison between groups of patients with migraine in the episode or interictal phases, and healthy controls showed that both episode and interictal migraine groups had the similar HAM-A and HAM-D scores (P > 0.05), but higher than that in controls (P < 0.01). For ALFF values of Episode and Interictal groups, the Montreal Neurological Institute (MNI) coordinates of the decreased ALFF were (−9, 42, 9), the voxel size = 215, including the bilateral anterior cingulate cortex (ACC), T =−4.15, without significant differences. Patients in Interictal group were with a stronger activation at MNI coordinates (12, 51, 12), in the bilateral ACC, voxel size = 90, T =3.87. </sec> <sec> <title>Conclusion:</title> ACC plays an adaptive, regulatory role in migraine and is related to multiple brain regions, which may mediate activation through descending anti-nociceptive pathways. ACC is related to opioid receptor and glutamate excitatory regulation. </sec>

The Cerebrovascular Reactivity-Adjusted Spontaneous Brain Activity Abnormalities in White Matter Hyperintensities Related Cognitive Impairment: A Resting-State Functional MRI Study

BACKGROUND

The BOLD signal is regulated by neuronal activity and vascular physiology. The evolution pattern of brain activities after modulating the vascular factors in white matter hyperintensities (WMHs) related cognitive impairment (CI) was unknown.

OBJECTIVE

To explore the "pure" low-frequency fluctuation (ALFF) alterations after adjusting the cerebrovascular reactivity (CVR) factor.

METHODS

In this study, 111 WMHs subjects including 55 with CI (WMH-CI) and 56 without CI (WMH-no-CI), and 72 normal controls (NCs) underwent resting-state fMRI. The CVR and ALFF maps were derived using BOLD data. A voxel-wise Pearson analysis was performed to detect the relationship between CVR and ALFF maps. The ANCOVA analysis with and without CVR as a covariate was conducted to explore the effect of CVR on ALFF analysis. Correlation between the ALFF alterations and cognitive performance was conducted in WMH-CI subjects. The receiver operating characteristic curve was constructed to assess the diagnostic performance of ALFF indexes to determine the occurrence of CI.

RESULTS

There was a significant widespread correlation between the CVR and ALFF maps. The ALFF alterations between the WMH groups and NC group with CVR as covariate were more than those without CVR as covariate. WMH-CI subjects showed further ALFF alterations when compared with WMH-no-CI subjects. The abnormal ALFF values were significantly associated with poor performance. The combination of inferior frontal gyrus and middle frontal gyrus to PCC provided an incremental contribution to the occurrence of CI.

CONCLUSION

More areas with abnormal ALFF values which were specific to the WMHs related cognitive dysfunction were detected when considering the impact of CVR.

Aberrant Amplitude of Low-Frequency Fluctuation and Degree Centrality within the Default Mode Network in Patients with Vascular Mild Cognitive Impairment

This study aimed to investigate whole-brain spontaneous activities changes in patients with vascular mild cognitive impairment (VaMCI), and to evaluate the relationships between these brain alterations and their neuropsychological assessments. Thirty-one patients with VaMCI and thirty-one healthy controls (HCs) underwent structural MRI and resting-state functional MRI (rs-fMRI) and neuropsychological assessments. The functional alterations were determined by the amplitude of low-frequency fluctuation (ALFF) and degree centrality (DC). The gray matter volume (GMV) changes were analyzed using voxel-based morphometry (VBM). Linear regression analysis was used to evaluate the relationships between the structural and functional changes of brain regions and neuropsychological assessments. The VaMCI group had significantly lower scores in the Montreal Cognitive Assessment (MoCA), and higher scores on the Hamilton Anxiety Rating Scale (HAMA) and Hamilton Depression Rating Scale (HAMD). Compared to the HCs, the VaMCI group exhibited GM atrophy in the right precentral gyrus (PreCG) and right inferior temporal gyrus (ITG). VaMCI patients further exhibited significantly decreased brain activity within the default mode network (DMN), including the bilateral precuneus (PCu), angular gyrus (AG), and medial frontal gyrus (medFG). Linear regression analysis revealed that the decreased ALFF was independently associated with lower MoCA scores, and the GM atrophy was independently associated with higher HAMD scores. The current finding suggested that aberrant spontaneous brain activity in the DMN might subserve as a potential biomarker of VaMCI, which may highlight the underlying mechanism of cognitive decline in cerebral small vessel disease.

An ALE Meta-Analysis of Specific Functional MRI Studies on Subcortical Vascular Cognitive Impairment

Background: Subcortical vascular cognitive impairment (sVCI), caused by cerebral small vessel disease, accounts for the majority of vascular cognitive impairment, and is characterized by an insidious onset and impaired memory and executive function. If not recognized early, it inevitably develops into vascular dementia. Several quantitative studies have reported the consistent results of brain regions in sVCI patients that can be used to predict dementia conversion. The purpose of the study was to explore the exact abnormalities within the brain in sVCI patients by combining the coordinates reported in previous studies.

Methods: The PubMed, Embase, and Web of Science databases were thoroughly searched to obtain neuroimaging articles on the amplitude of low-frequency fluctuation, regional homogeneity, and functional connectivity in sVCI patients. According to the activation likelihood estimation (ALE) algorithm, a meta-analysis based on coordinate and functional connectivity modeling was conducted.

Results: The quantitative meta-analysis included 20 functional imaging studies on sVCI patients. Alterations in specific brain regions were mainly concentrated in the frontal lobes including the middle frontal gyrus, superior frontal gyrus, medial frontal gyrus, and precentral gyrus; parietal lobes including the precuneus, angular gyrus, postcentral gyrus, and inferior parietal lobule; occipital lobes including the lingual gyrus and cuneus; temporal lobes including the fusiform gyrus and middle temporal gyrus; and the limbic system including the cingulate gyrus. These specific brain regions belonged to important networks known as the default mode network, the executive control network, and the visual network.

Conclusion: The present study determined specific abnormal brain regions in sVCI patients, and these brain regions with specific changes were found to belong to important brain functional networks. The findings objectively present the exact abnormalities within the brain, which help further understand the pathogenesis of sVCI and identify them as potential imaging biomarkers. The results may also provide a basis for new approaches to treatment.

Altered Patterns of Amplitude of Low-Frequency Fluctuations and Fractional Amplitude of Low-Frequency Fluctuations Between Amnestic and Vascular Mild Cognitive Impairment: An ALE-Based Comparative Meta-Analysis

Background: Changes in the amplitude of low-frequency fluctuations (ALFF) and the fractional amplitude of low-frequency fluctuations (fALFF) have provided stronger evidence for the pathophysiology of cognitive impairment. Whether the altered patterns of ALFF and fALFF differ in amnestic cognitive impairment (aMCI) and vascular mild cognitive impairment (vMCI) is largely unknown. The purpose of this study was to explore the ALFF/fALFF changes in the two diseases and to further explore whether they contribute to the diagnosis and differentiation of these diseases.

Methods: We searched PubMed, Ovid, and Web of Science databases for articles on studies using the ALFF/fALFF method in patients with aMCI and vMCI. Based on the activation likelihood estimation (ALE) method, connectivity modeling based on coordinate meta-analysis and functional meta-analysis was carried out.

Results: Compared with healthy controls (HCs), patients with aMCI showed increased ALFF/fALFF in the bilateral parahippocampal gyrus/hippocampus (PHG/HG), right amygdala, right cerebellum anterior lobe (CAL), left middle temporal gyrus (MTG), left cerebrum temporal lobe sub-gyral, left inferior temporal gyrus (ITG), and left cerebrum limbic lobe uncus. Meanwhile, decreased ALFF/fALFF values were also revealed in the bilateral precuneus (PCUN), bilateral cuneus (CUN), and bilateral posterior cingulate (PC) in patients with aMCI. Compared with HCs, patients with vMCI predominantly showed decreased ALFF/fALFF in the bilateral CUN, left PCUN, left PC, and right cingulate gyrus (CG).

Conclusions: The present findings suggest that ALFF and fALFF displayed remarkable altered patterns between aMCI and vMCI when compared with HCs. Thus, the findings of this study may serve as a reliable tool for distinguishing aMCI from vMCI, which may help understand the pathophysiological mechanisms of these diseases.

Neuroimaging Anomalies in Community-Dwelling Asymptomatic Adults With Very Early-Stage White Matter Hyperintensity

White matter hyperintensity (WMH) is common in healthy adults in their 60s and can be seen as early as in their 30s and 40s. Alterations in the brain structural and functional profiles in adults with WMH have been repeatedly studied but with a focus on late-stage WMH. To date, structural and functional MRI profiles during the very early stage of WMH remain largely unexplored. To address this, we investigated multimodal MRI (structural, diffusion, and resting-state functional MRI) profiles of community-dwelling asymptomatic adults with very early-stage WMH relative to age-, sex-, and education-matched non-WMH controls. The comparative results showed significant age-related and age-independent changes in structural MRI-based morphometric measures and resting-state fMRI-based measures in a set of specific gray matter (GM) regions but no global white matter changes. The observed structural and functional anomalies in specific GM regions in community-dwelling asymptomatic adults with very early-stage WMH provide novel data regarding very early-stage WMH and enhance understanding of the pathogenesis of WMH.

Brain Functional Changes in Stroke Following Rehabilitation Using Brain-Computer Interface-Assisted Motor Imagery With and Without tDCS: A Pilot Study

Brain-computer interface-assisted motor imagery (MI-BCI) or transcranial direct current stimulation (tDCS) has been proven effective in post-stroke motor function enhancement, yet whether the combination of MI-BCI and tDCS may further benefit the rehabilitation of motor functions remains unknown. This study investigated brain functional activity and connectivity changes after a 2 week MI-BCI and tDCS combined intervention in 19 chronic subcortical stroke patients. Patients were randomized into MI-BCI with tDCS group and MI-BCI only group who underwent 10 sessions of 20 min real or sham tDCS followed by 1 h MI-BCI training with robotic feedback. We derived amplitude of low-frequency fluctuation (ALFF), regional homogeneity (ReHo), and functional connectivity (FC) from resting-state functional magnetic resonance imaging (fMRI) data pre- and post-intervention. At baseline, stroke patients had lower ALFF in the ipsilesional somatomotor network (SMN), lower ReHo in the contralesional insula, and higher ALFF/Reho in the bilateral posterior default mode network (DMN) compared to age-matched healthy controls. After the intervention, the MI-BCI only group showed increased ALFF in contralesional SMN and decreased ALFF/Reho in the posterior DMN. In contrast, no post-intervention changes were detected in the MI-BCI + tDCS group. Furthermore, higher increases in ALFF/ReHo/FC measures were related to better motor function recovery (measured by the Fugl-Meyer Assessment scores) in the MI-BCI group while the opposite association was detected in the MI-BCI + tDCS group. Taken together, our findings suggest that brain functional re-normalization and network-specific compensation were found in the MI-BCI only group but not in the MI-BCI + tDCS group although both groups gained significant motor function improvement post-intervention with no group difference. MI-BCI and tDCS may exert differential or even opposing impact on brain functional reorganization during post-stroke motor rehabilitation; therefore, the integration of the two strategies requires further refinement to improve efficacy and effectiveness.

Brain function state in different phases and its relationship with clinical symptoms of migraine: an fMRI study based on regional homogeneity (ReHo)

Background

Using fMRI to analysis of brain function state in migraineurs at different phases, and combined with the clinical symptoms to explore the mechanisms and outcomes of migraine.

Methods

It’s a case-control study. We analyzed the resting-state brain functional magnetic resonance imaging in 19 patients with episodes, 22 patients with interictal phase, and 22 healthy controls. The ReHo method was used for post-processing. All subjects were evaluated using the Montreal cognitive assessment (MoCA) scale, simple mental state examination (MMSE), Hamilton anxiety (HAMA) scale, and Hamilton depression (HAMD) scale. The subjects’ clinical indicators (such as frequency of attack, course of disease, duration of each headache, and severity of headache) were correlated with the ReHo values of brain regions. This study was approved by the ethics committee of Yangtze River Shipping General Hospital.

Results

Compared with the interictal, patients in the episode group had lower activation in bilateral anterior cingulate cortex (ACC), with Montreal Neurological Institute (MNI) (−9, 42, 15); and had stronger activation in bilateral paracentral lobule (PCL), with MNI (−3, −24, 66). Compared with the control group, patients in interictal phase had lower activation in the bilateral cuneus and bilateral lingual gyrus, with MNI scores of (9, −84, 36) and (0, −72, 6), respectively. No significant difference in brain area was found between the episodes group and the control group. In the episodes group, a significant correlation was observed between attack frequency and ReHo value of the bilateral PCL (r=0.492; P=0.038).

Conclusions

We need to observe the course of migraine as a whole. In the interictal period, the cuneus and lingual gyrus may affect the development of the disease. The ACC regulates different states of migraine by inducing anti-injury sensation regulation function. The paracentric lobule is not only associated with migraine attacks, but also with the frequency. This may have an effect on the outcome of subsequent migraines, as well as whether the condition becomes chronic, and the remodeling of the brain.

Association between cortical thickness and distinct vascular cognitive impairment and dementia in patients with white matter lesions

NEW FINDINGS

What is the central question of this study? White matter lesions (WMLs) are a brain disease characterized by altered brain structural and functional connectivity, but findings have shown an inconsistent pattern: are there distinct cortical thickness changes in patients with WMLs subtypes? What is the main finding and its importance? Patients with WMLs with non-dementia vascular cognitive impairment and WMLs with vascular dementia showed distinct pathophysiology in cortical thickness. These neural correlates of WMLs should be considered in future treatment.

ABSTRACT

The effect of cortical thickness on white matter lesions (WMLs) in patients with distinct vascular cognitive impairments is relatively unknown. This study investigated the correlation between cortical thickness and vascular cognitive manifestations. WML patients and healthy controls from Beijing Tiantan Hospital between 2014 and 2018 were included. The patients were further divided into two subgroups, namely WMLs with non-dementia vascular cognitive impairment (WML-VCIND) and WMLs with vascular dementia (WML-VaD) according to the Clinical Dementia Rating (CDR) scale and the Beijing version of the Montreal Cognitive Assessment (MoCA). Changes in cortical thickness were calculated using FreeSurfer. Pearson's correlation analysis was performed to explore the relationship between cognitive manifestations and cortical thickness in WML patients. Forty-five WML patients and 23 healthy controls were recruited. The WML group exhibited significant difference in cortical thickness compared to the control group. Significantly decreased cortical thickness in the middle and superior frontal gyri, middle temporal gyrus, angular gyrus and insula was found in the WML-VaD versus WML-VCIND subgroup. Cortical thickness deficits of the left caudal middle frontal gyrus (r = 0.451, P = 0.002), left rostral middle frontal gyrus (r = 0.514, P < 0.001), left superior frontal gyrus (r = 0.410, P = 0.006), right middle temporal gyrus (r = 0.440, P = 0.003), right pars triangularis (r = 0.462, P = 0.002), right superior frontal gyrus (r = 0.434, P = 0.004) and right insula (r = 0.499, P = 0.001) were positively correlated with the MoCA score in WML patients. The specific pattern of cortical thickness deficits in the WML-VaD subgroup revealed the pathophysiology of WMLs, which should be considered in future treatment of WMLs.

Irradiation-related longitudinal white matter atrophy underlies cognitive impairment in patients with nasopharyngeal carcinoma

To longitudinally investigate alterations in cerebral white matter volume as a function of irradiation dose and time after standard radiotherapy in nasopharyngeal carcinoma patients and to determine how these alterations are related to radiotherapy-associated neurocognitive dysfunction.A total of 120 nasopharyngeal carcinoma patients were included in the present study. Longitudinal structural magnetic resonance imaging was performed at pre-radiotherapy and 1-3, 6, and 9-12 months post-radiotherapy. Twenty healthy controls were recruited and followed up with in parallel. Structural images were processed via FreeSurfer. The Montreal Cognitive Assessment was performed to evaluate cognitive function of the participants. Linear mixed models and general linear models were used to evaluate different trajectories and the relationship between white matter volume and cognition in patients and controls within approximately 12 months of follow-up.Selective and time-dependent white matter atrophy was observed in the right parahippocampal gyrus, right inferior temporal gyrus, right middle temporal gyrus, right fusiform gyrus, and left insular cortex in post-radiotherapy patients compared to the controls. Moreover, radiotherapy-associated white matter atrophy in the right parahippocampal gyrus exhibited a dose-dependent pattern, whereas radiotherapy-associated white matter atrophy in the right inferior temporal gyrus was correlated with progressive cognitive impairment in patients.Taken together, our findings illustrate that white matter volume alterations can be used as a potential biomarker to detect radiotherapy-related subtle brain injury in nasopharyngeal carcinoma patients, which may help further elucidate the pathogenesis of radiation-induced cognitive decline and facilitate studies on cognition-sparing radiotherapy.

Cerebrovascular Reactivity Mapping Without Gas Challenges: A Methodological Guide

Cerebrovascular reactivity (CVR) is defined as the ability of vessels to alter their caliber in response to vasoactive factors, by means of dilating or constricting, in order to increase or decrease regional cerebral blood flow (CBF). Importantly, CVR may provide a sensitive biomarker for pathologies where vasculature is compromised. Furthermore, the spatiotemporal dynamics of CVR observed in healthy subjects, reflecting regional differences in cerebral vascular tone and response, may also be important in functional MRI studies based on neurovascular coupling mechanisms. Assessment of CVR is usually based on the use of a vasoactive stimulus combined with a CBF measurement technique. Although transcranial Doppler ultrasound has been frequently used to obtain global flow velocity measurements, MRI techniques are being increasingly employed for obtaining CBF maps. For the vasoactive stimulus, vasodilatory hypercapnia is usually induced through the manipulation of respiratory gases, including the inhalation of increased concentrations of carbon dioxide. However, most of these methods require an additional apparatus and complex setups, which not only may not be well-tolerated by some populations but are also not widely available. For these reasons, strategies based on voluntary breathing fluctuations without the need for external gas challenges have been proposed. These include the task-based methodologies of breath holding and paced deep breathing, as well as a new generation of methods based on spontaneous breathing fluctuations during resting-state. Despite the multitude of alternatives to gas challenges, existing literature lacks definitive conclusions regarding the best practices for the vasoactive modulation and associated analysis protocols. In this work, we perform an extensive review of CVR mapping techniques based on MRI and CO2 variations without gas challenges, focusing on the methodological aspects of the breathing protocols and corresponding data analysis. Finally, we outline a set of practical guidelines based on generally accepted practices and available data, extending previous reports and encouraging the wider application of CVR mapping methodologies in both clinical and academic MRI settings.

Altered amplitude of low-frequency fluctuations and default mode network connectivity in high myopia: a resting-state fMRI study

AIM

To analyze changes in amplitude of low-frequency fluctuations (ALFFs) and default mode network (DMN) connectivity in the brain, using resting-state functional magnetic resonance imaging (rs-fMRI), in high myopia (HM) patients.

METHODS

Eleven patients with HM (HM group) and 15 age- and sex-matched non-HM controls (non-HM group) were recruited. ALFFs were calculated and compared between HM group and non-HM group. Independent component analysis (ICA) was conducted to identify DMN, and comparisons between DMNs of two groups were performed. Region-of-interest (ROI)-based analysis was performed to explore functional connectivity (FC) between DMN regions.

RESULTS

Significantly increased ALFFs in left inferior temporal gyrus (ITG), bilateral rectus gyrus (REC), bilateral middle temporal gyrus (MTG), left superior temporal gyrus (STG), and left angular gyrus (ANG) were detected in HM group compared with non-HM group (all P<0.01). HM group showed increased FC in the posterior cingulate gyrus (PCC)/precuneus (preCUN) and decreased FC in the left medial prefrontal cortex (mPFG) within DMN compared with non-HM group (all P<0.01). Compared with non-HM group, HM group showed higher FC between mPFG and bilateral middle frontal gyrus (MFG), ANG, and MTG (all P<0.01). In addition, HM patients showed higher FC between PCC/(preCUN) and the right cerebellum, superior frontal gyrus (SFG), left preCUN, superior frontal gyrus (SFG), and medial orbital of the superior frontal gyrus (ORB supmed; all P<0.01).

CONCLUSION

HM patients show different ALFFs and DMNs compared with non-HM subjects, which may imply the cognitive alterations related to HM.

Abnormal Interactions of the Salience Network, Central Executive Network, and Default-Mode Network in Patients With Different Cognitive Impairment Loads Caused by Leukoaraiosis

Leukoaraiosis (LA) is associated with cognitive impairment in the older people which can be demonstrated in functional connectivity (FC) based on resting-state functional magnetic resonance imaging (rs-fMRI). This study is to explore the FC changes in LA patients with different cognitive status by three network models. Fifty-three patients with LA were divided into three groups: the normal cognition (LA-NC; n = 14, six males), mild cognitive impairment (LA-MCI; n = 27, 13 males), and vascular dementia (LA-VD; n = 12, six males), according to the Mini Mental State Exam (MMSE) and Clinical Dementia Rating (CDR). The three groups and 30 matched healthy controls (HCs; 11 males) underwent rs-fMRI. The data of rs-fMRI were analyzed by independent components analysis (ICA) and region of interest (ROI) analysis by the REST toolbox. Then the FC was respectively analyzed by the default-mode network (DMN), salience networks (SNs) and the central executive network (CEN) with their results compared among the different groups. For inter-brain network analysis, there were negative FC between the SN and DMN in LA groups, and the FC decreased when compared with HC group. While there were enhanced inter-brain network FC between the SN and CEN as well as within the SN. The FC in patients with LA can be detected by different network models of rs-fMRI. The multi-model analysis is helpful for the further understanding of the cognitive changes in those patients.