Tag: brain connectivity

Brain and cognitive changes in patients with long COVID compared with infection-recovered control subjects

Abstract:

Between 2.5 and 28% of people infected with SARS-CoV-2 suffer Long COVID or persistence of symptoms for months after acute illness. Many symptoms are neurological, but the brain changes underlying the neuropsychological impairments remain unclear. This study aimed to provide a detailed description of the cognitive profile, the pattern of brain alterations in Long COVID and the potential association between them.

To address these objectives, 83 patients with persistent neurological symptoms after COVID-19 were recruited, and 22 now healthy controls chosen because they had suffered COVID-19 but did not experience persistent neurological symptoms. Patients and controls were matched for age, sex and educational level. All participants were assessed by clinical interview, comprehensive standardized neuropsychological tests and structural MRI. The mean global cognitive function of patients with Long COVID assessed by ACE III screening test (Overall Cognitive level – OCLz= -0.39± 0.12) was significantly below the infection recovered-controls (OCLz= +0.32± 0.16, p< 0.01).

We observed that 48% of patients with Long COVID had episodic memory deficit, with 27% also impaired overall cognitive function, especially attention, working memory, processing speed and verbal fluency. The MRI examination included grey matter morphometry and whole brain structural connectivity analysis. Compared to infection recovered controls, patients had thinner cortex in a specific cluster centred on the left posterior superior temporal gyrus.

In addition, lower fractional anisotropy (FA) and higher radial diffusivity (RD) were observed in widespread areas of the patients’ cerebral white matter relative to these controls. Correlations between cognitive status and brain abnormalities revealed a relationship between altered connectivity of white matter regions and impairments of episodic memory, overall cognitive function, attention and verbal fluency.

This study shows that patients with neurological Long COVID suffer brain changes, especially in several white matter areas, and these are associated with impairments of specific cognitive functions.

Source: Serrano Del Pueblo VM, Serrano-Heras G, Romero Sánchez CM, Piqueras Landete P, Rojas-Bartolome L, Feria I, Morris RGM, Strange B, Mansilla F, Zhang L, Castro-Robles B, Arias-Salazar L, López-López S, Payá M, Segura T, Muñoz-López M. Brain and cognitive changes in patients with long COVID compared with infection-recovered control subjects. Brain. 2024 Apr 2:awae101. doi: 10.1093/brain/awae101. Epub ahead of print. PMID: 38562097. https://pubmed.ncbi.nlm.nih.gov/38562097/

Neuroinflammatory imaging markers in white matter: insights into the cerebral consequences of post-acute sequelae of COVID-19 (PASC)

Abstract:

Symptoms of coronavirus disease 2019 (COVID-19) can persist for months or years after infection, a condition called Post-Acute Sequelae of COVID-19 (PASC). Whole-brain white matter and cortical gray matter health were assessed using multi-shell diffusion tensor imaging. Correlational tractography was utilized to dissect the nature and extent of white matter changes.

In this study of 42 male essential workers, the most common symptoms of Neurological PASC (n = 24) included fatigue (n = 19) and headache (n = 17). Participants with neurological PASC demonstrated alterations to whole-brain white matter health when compared to controls made up of uninfected, asymptomatic, or mildly infected controls (n = 18). Large differences were evident between PASC and controls in measures of fractional anisotropy (Cohen’s D=-0.54, P = 0.001) and cortical isotropic diffusion (Cohen’s D = 0.50, P = 0.002).

Symptoms were associated with white matter fractional anisotropy (fatigue: rho = -0.62, P < 0.001; headache: rho = -0.66, P < 0.001), as well as nine other measures of white and gray matter health. Brain fog was associated with improved cerebral functioning including improved white matter isotropic diffusion and quantitative anisotropy.

This study identified changes across measures of white and gray matter connectivity, neuroinflammation, and cerebral atrophy that were interrelated and associated with differences in symptoms of PASC. These results provide insights into the long-term cerebral implications of COVID-19.

Source: Sean Clouston, Chuan Huang, Jia Ying et al. Neuroinflammatory imaging markers in white matter: insights into the cerebral consequences of post-acute sequelae of COVID-19 (PASC), 19 January 2024, PREPRINT (Version 1) available at Research Square [https://doi.org/10.21203/rs.3.rs-3760289/v1] https://www.researchsquare.com/article/rs-3760289/v1 (Full text)

Subcortical and Default Mode Network connectivity is impaired in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Abstract:

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex chronic condition with core symptoms of fatigue, and cognitive dysfunction suggesting a key role for the central nervous system, in the pathophysiology of this disease. Several studies have reported altered functional connectivity (FC) related to motor and cognitive deficits in ME/CFS patients. In this study, we compared functional connectivity differences between 31 ME/CFS and 15 healthy controls (HC) using 7 Tesla MRI. Functional scans were acquired during a cognitive Stroop color-word task and blood oxygen level-dependent (BOLD) time-series were computed for 27 regions of interest (ROIs) in the cerebellum, brainstem, and salience and default mode networks.

Region-based comparison detected reduced FC between the pontine nucleus and cerebellum vermis IX (p=0.027) for ME/CFS patients compared to HC. Our ROI-to-voxel analysis found significant impairment of FC within ponto-cerebellar regions in ME/CFS. Correlation analyses of connectivity with clinical scores in ME/CFS patients detected associations of FC with ‘duration of illness’ and ‘memory scores’ in salience network hubs and cerebellum vermis, and with ‘respiratory rate’ within medulla and the default mode network FC.

This novel investigation is the first to report extensive involvement of aberrant ponto-cerebellar connections consistent with ME/CFS symptomatology. This highlights the involvement of the brainstem and the cerebellum in the pathomechanism of ME/CFS.

Source: Maira INDERYAS, Kiran Thapaliya, Sonya Marshall-Gradisnik, Markus Barth, Leighton Barnden. Subcortical and Default Mode Network connectivity is impaired in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Front. Neurosci. Sec. Brain Imaging Methods. Volume 17 – 2023 | doi: 10.3389/fnins.2023.1318094 https://www.frontiersin.org/articles/10.3389/fnins.2023.1318094/full (Full text)

Altered functional brain connectivity, efficiency, and information flow associated with brain fog after mild to moderate COVID-19 infection

Abstract:

COVID-19 is associated with increased risk for cognitive decline but very little is known regarding the neural mechanisms of this risk. We enrolled 49 adults (55% female, mean age = 30.7 +/- 8.7), 25 with and 24 without a history of COVID-19 infection. We administered standardized tests of cognitive function and acquired brain connectivity data using MRI.

The COVID-19 group demonstrated significantly lower cognitive function (W = 475, p < 0.001, effect size r = 0.58) and lower functional connectivity in multiple brain regions (mean t = 3.47 +/- 0.36, p = 0.03, corrected, effect size d = 0.92 to 1.5). Hypo-connectivity of these regions was inversely correlated with subjective cognitive function and directly correlated with fatigue (p < 0.05, corrected). These regions demonstrated significantly reduced local efficiency (p < 0.026, corrected) and altered effective connectivity (p < 0.001, corrected).

COVID-19 may have a widespread effect on the functional connectome characterized by lower functional connectivity and altered patterns of information processing efficiency and effective information flow. This may serve as an adaptation to the pathology of SARS-CoV-2 wherein the brain can continue functioning at near expected objective levels, but patients experience lowered efficiency as brain fog.

Source: Shelli R. Kesler, Oscar Y. Franco Rocha, Alexa De La Torre Schutz et al. Altered functional brain connectivity, efficiency, and information flow associated with brain fog after mild to moderate COVID-19 infection, 20 October 2023, PREPRINT (Version 1) available at Research Square [https://doi.org/10.21203/rs.3.rs-3466991/v1] https://www.researchsquare.com/article/rs-3466991/v1 (Full text)

Altered brain connectivity in Long Covid during cognitive exertion: a pilot study

Abstract:

Introduction: Debilitating Long-Covid symptoms occur frequently after SARS-COVID-19 infection.

Methods: Functional MRI was acquired in 10 Long Covid (LCov) and 13 healthy controls (HC) with a 7 Tesla scanner during a cognitive (Stroop color-word) task. BOLD time series were computed for 7 salience and 4 default-mode network hubs, 2 hippocampus and 7 brainstem regions (ROIs). Connectivity was characterized by the correlation coefficient between each pair of ROI BOLD time series. We tested for HC versus LCov differences in connectivity between each pair of the 20 regions (ROI-to-ROI) and between each ROI and the rest of the brain (ROI-to-voxel). For LCov, we also performed regressions of ROI-to-ROI connectivity with clinical scores.

Results: Two ROI-to-ROI connectivities differed between HC and LCov. Both involved the brainstem rostral medulla, one connection to the midbrain, another to a DM network hub. Both were stronger in LCov than HC. ROI-to-voxel analysis detected multiple other regions where LCov connectivity differed from HC located in all major lobes. Most, but not all connections, were weaker in LCov than HC. LCov, but not HC connectivity, was correlated with clinical scores for disability and autonomic function and involved brainstem ROI.

Discussion: Multiple connectivity differences and clinical correlations involved brainstem ROIs. Stronger connectivity in LCov between the medulla and midbrain may reflect a compensatory response. This brainstem circuit regulates cortical arousal, autonomic function and the sleep-wake cycle. In contrast, this circuit exhibited weaker connectivity in ME/CFS. LCov connectivity regressions with disability and autonomic scores were consistent with altered brainstem connectivity in LCov.

Source: Barnden L, Thapaliya K, Eaton-Fitch N, Barth M, Marshall-Gradisnik S. Altered brain connectivity in Long Covid during cognitive exertion: a pilot study. Front Neurosci. 2023 Jun 22;17:1182607. doi: 10.3389/fnins.2023.1182607. PMID: 37425014; PMCID: PMC10323677. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10323677/ (Full text)

Altered Effective Connectivity of Resting-State Networks by Tai Chi Chuan in Chronic Fatigue Syndrome Patients: A Multivariate Granger Causality Study

Abstract:

Numerous evidence has shown that patients with chronic fatigue syndrome (CFS) have changes in resting brain functional connectivity, but there is no study on the brain network effect of Tai Chi Chuan intervention in CFS. To explore the influence of Tai Chi Chuan exercise on the causal relationship between brain functional networks in patients with CFS, 21 patients with CFS and 19 healthy controls were recruited for resting-state functional magnetic resonance imaging (rs-fMRI) scanning and 36-item Short-Form Health Survey (SF-36) scale assessment before and after 1month-long training in Tai Chi Chuan.

We extracted the resting brain networks using the independent component analysis (ICA) method, analyzed the changes of FC in these networks, conducted Granger causality analysis (GCA) on it, and analyzed the correlation between the difference causality value and the SF-36 scale. Compared to the healthy control group, the SF-36 scale scores of patients with CFS were lower at baseline. Meanwhile, the causal relationship between sensorimotor network (SMN) and default mode network (DMN) was weakened. ‘

The above abnormalities could be improved by Tai Chi Chuan training for 1 month. In addition, the correlation analyses showed that the causal relationship between SMN and DMN was positively correlated with the scores of Role Physical (RP) and Bodily Pain (BP) in CFS patients, and the change of causal relationship between SMN and DMN before and after training was positively correlated with the change of BP score.

The findings suggest that Tai Chi Chuan is helpful to improve the quality of life for patients with CFS. The change of Granger causality between SMN and DMN may be a readout parameter of CFS. Tai Chi Chuan may promote the functional plasticity of brain networks in patients with CFS by regulating the information transmission between them.

Source: Li Y, Wu K, Hu X, Xu T, Li Z, Zhang Y, Li K. Altered Effective Connectivity of Resting-State Networks by Tai Chi Chuan in Chronic Fatigue Syndrome Patients: A Multivariate Granger Causality Study. Front Neurol. 2022 Jun 3;13:858833. doi: 10.3389/fneur.2022.858833. PMID: 35720086; PMCID: PMC9203735. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9203735/ (Full text)

Brain correlates of subjective cognitive complaints in COVID-19 survivors: A multimodal magnetic resonance imaging study

Abstract:

Cognitive impairment represents a leading residual symptom of COVID-19 infection, which lasts for months after the virus clearance. Up-to-date scientific reports documented a wide spectrum of brain changes in COVID-19 survivors following the illness’s resolution, mainly related to neurological and neuropsychiatric consequences.

Preliminary insights suggest abnormal brain metabolism, microstructure, and functionality as neural under-layer of post-acute cognitive dysfunction. While previous works focused on brain correlates of impaired cognition as objectively assessed, herein we investigated long-term neural correlates of subjective cognitive decline in a sample of 58 COVID-19 survivors with a multimodal imaging approach.

Diffusion Tensor Imaging (DTI) analyses revealed widespread white matter disruption in the sub-group of cognitive complainers compared to the non-complainer one, as indexed by increased axial, radial, and mean diffusivity in several commissural, projection and associative fibres. Likewise, the Multivoxel Pattern Connectivity analysis (MVPA) revealed highly discriminant patterns of functional connectivity in resting-state among the two groups in the right frontal pole and in the middle temporal gyrus, suggestive of inefficient dynamic modulation of frontal brain activity and possible metacognitive dysfunction at rest.

Beyond COVID-19 actual pathophysiological brain processes, our findings point toward brain connectome disruption conceivably translating into clinical post-COVID cognitive symptomatology. Our results could pave the way for a potential brain signature of cognitive complaints experienced by COVID-19 survivors, possibly leading to identify early therapeutic targets and thus mitigating its detrimental long-term impact on quality of life in the post-COVID-19 stages.

Source: Paolini M, Palladini M, Mazza MG, Colombo F, Vai B, Rovere-Querini P, Falini A, Poletti S, Benedetti F. Brain correlates of subjective cognitive complaints in COVID-19 survivors: A multimodal magnetic resonance imaging study. Eur Neuropsychopharmacol. 2022 Dec 12;68:1-10. doi: 10.1016/j.euroneuro.2022.12.002. Epub ahead of print. PMID: 36640728. https://www.sciencedirect.com/science/article/pii/S0924977X22009130 (Full study)

Investigating the neural substrates of Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) : a structural and functional MRI study

Abstract:

Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) is characterised by continuous fatigue and has many diagnostic criteria. Cognitive dysfunction affects 86-94% of adults with CFS/ME.

This thesis used MRI applications to investigate brain structure and function in CFS/ME. This thesis hypothesised to find brain volume differences, functional connectivity differences in brain networks, and functional differences measured by Blood Oxygenation Level Dependant (BOLD) signal activation during working memory task performance.

The working memory paradigm was designed to investigate working memory components, processing and storage separately and combined. The relationship between fatigue and performance was assessed. This thesis’s original contribution provides evidence that the salience network might have altered resting-state functional connectivity in CFS/ME in the absence of morphological differences.

The salience network is involved in detecting and integrating salient sensory information; therefore, disruption in this network might disrupt incoming cognitive stimuli and influence other networks’ connectivity, involved in fatigue and impaired memory.

In the more demanding task, participants with CFS/ME were slower and less accurate but used the same working memory network as healthy controls. No brain volume differences, nor atrophy were found. The differences between these findings compared to previous studies might be due to different study designs, analysis methods, sample sizes with different symptoms, including illness duration, physical inactivity and sleep disturbance.

The salience network alteration could potentially have a significant role in CFS/ME, as we cannot determine cause and effect with current experimental design the association with fatigue and other CFS/ME symptoms remains unclear. Using longitudinal studies that account for neurologically relevant confounders are needed in CFS/ME to further investigate the role of salience network.

Source: Almutairi, Basim S. Investigating the neural substrates of Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) : a structural and functional MRI study. PhD Thesis, University of Bristol. uk.bl.ethos.866683  https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.866683

Connectivity between Salience and Default Mode Networks and subcortical nodes distinguishes between two classes of ME/CFS

Abstract:

Myalgic Encephalomyelitis or Chronic Fatigue Syndrome (ME/CFS) is a debilitating disease with unknown pathophysiology. Functional MRI (fMRI) studies in ME/CFS have reported disparate connectivities for the brain salience (SA) and default mode (DMN) networks.

In this study, we acquired resting state and task fMRI with an advanced scanner for improved subject numbers: 24 healthy controls (HC) and 42 ME/CFS patients, 18 meeting International Consensus Criteria (ICC) and 24 meeting Fukuda criteria. We evaluated mean FC between SA and DMN network hub, and subcortical regions known to be involved in ME/CFS. We tested the hypothesis that ME/CFS connectivity differed from HC and the ICC and Fukuda classes are distinguished by different connectivities with HC for different pairs of SA, DMN or subcortical hubs.

During resting state fMRI only two connections differed from HC, both for Fukuda ME/CFS and both with an SA hub. During task fMRI 10 ME/CFS connections differed from HC, 5 for ICC and 5 for Fukuda. None were common to both classes. Eight of the 10 different connections involved an SA hub, six of 10 were weaker in ME/CFS, 4 stronger.

SA connections to the hippocampus and brainstem reticular activation system (RAS) differed from and were stronger than HC. The SA mediates the relative activity of the DMN and executive networks and imbalance will have functional consequences. The RAS and hippocampus modulate cortical activation. Different regulatory connections are consistent with the impaired cognitive performance and sleep-wake cycle of ME/CFS. Different neuropathology is involved in ICC and Fukuda classes.

Source: Su J, Thapaliya K, Eaton-Fitch N, Marshall-Gradisnik SM, Barnden LR. Connectivity between Salience and Default Mode Networks and subcortical nodes distinguishes between two classes of ME/CFS. Brain Connect. 2022 Nov 9. doi: 10.1089/brain.2022.0049. Epub ahead of print. PMID: 36352819. https://pubmed.ncbi.nlm.nih.gov/36352819/

Psychiatric and neurological complications of long COVID

Abstract:

COVID-19 was primarily considered a pulmonary disease with extrapulmonary manifestations. As the pandemic spread, there has been growing evidence that the disease affects various organs/systems, including the central and peripheral nervous systems. Accumulation of clinical data demonstrates that in a large population of survivors impairments in the function of one or more organs may persist for a long time, a phenomenon commonly known as post COVID or long COVID.

Fatigue and cognitive dysfunction, such as concentration problems, short-term memory deficits, general memory loss, a specific decline in attention, language and praxis abilities, encoding and verbal fluency, impairment of executive functions, and psychomotor coordination, are amongst the most common and debilitating features of neuropsychatric symptoms of post COVID syndrome. Several patients also suffer from compromised sleep, depression, anxiety and post-traumatic stress disorder. Patients with long COVID may demonstrate brain hypometabolism, hypoperfusion of the cerebral cortex and changes in the brain structure and functional connectivity.

Children and adolescents represent a minority of COVID-19 cases, so not surprisingly data on the long-term sequelae after SARS-CoV-2 infections in these age groups are scarce. Although the pathogenesis, clinical characteristics, epidemiology, and risk factors of the acute phase of COVID-19 have been largely explained, these areas are yet to be explored in long COVID. This review aims to provide an update on what is currently known about long COVID effects on mental health.

Source: Zawilska JB, Kuczyńska K. Psychiatric and neurological complications of long COVID. J Psychiatr Res. 2022 Oct 20;156:349-360. doi: 10.1016/j.jpsychires.2022.10.045. Epub ahead of print. PMID: 36326545; PMCID: PMC9582925. https://www.sciencedirect.com/science/article/pii/S0022395622005982 (Full text)