Neurovascular coupling in humans: Physiology, methodological advances and clinical implications

Sleep Alterations and Cognitive Decline

Sleep disturbances and cognitive decline are intricately connected, and both are prevalent in aging populations and individuals with neurodegenerative disorders such as Alzheimer's disease (AD) and other dementias. Sleep is vital for cognitive functions including memory consolidation, executive function, and attention. Disruption in these processes is associated with cognitive decline, although causal evidence is mixed. This review delves into the bidirectional relationship between alterations in sleep and cognitive impairment, exploring key mechanisms such as amyloid-β accumulation, tau pathology, synaptic homeostasis, neurotransmitter dysregulation, oxidative stress, and vascular contributions. Evidence from both experimental research and population-based studies underscores the necessity of early interventions targeting sleep to mitigate risks of neurodegenerative diseases. A deeper understanding of the interplay between sleep and cognitive health may pave the way for innovative strategies to prevent or reduce cognitive decline through improved sleep management.

Synergistic interactions between physical exercise intervention, innovative materials, and neurovascular coupling in bone repair and injury recovery: a comprehensive review

Bone injury presents a prevalent challenge in clinical settings, with traditional treatment modalities exhibiting inherent limitations. Recent advancements have highlighted the potential of combining physical exercise intervention and innovative materials to enhance bone repair and recovery. This review explores the synergistic effects of physical exercise and novel materials in promoting bone regeneration, with a particular focus on the role of neurovascular coupling (NVC) mechanisms. Physical exercise not only stimulates bone cell function and blood circulation but also enhances the bioactivity of novel materials, such as nanofiber membranes and smart materials, which provide supportive scaffolds for bone cell attachment, proliferation, and differentiation. NVC, involving the interaction between neural activity and blood flow, is integral to the bone repair process, ensuring the supply of nutrients and oxygen to the injured site. Studies demonstrate that the combination of physical exercise and novel materials can accelerate bone tissue regeneration, with exercise potentially enhancing the bioactivity of materials and materials improving the effectiveness of exercise. However, challenges remain in clinical applications, including patient variability, material biocompatibility, and long-term stability. Optimizing the integration of physical exercise and novel materials for optimal therapeutic outcomes is a key focus for future research. This review examines the collaborative mechanisms between physical exercise, novel materials, and NVC, emphasizing their potential and the ongoing challenges in clinical settings. Further exploration is needed to refine their application and improve bone repair strategies.

Sleep deprivation impairs neurovascular coupling and cerebral vasomotor reactivity

Sleep deficiency increases the risk of cerebrovascular diseases. However, the effects of sleep deprivation (SD) on cerebral blood flow have been poorly studied. We examined the effect of 24-h of SD on the resting posterior cerebral artery (PCA) and middle cerebral artery (MCA) flow velocities (FV), the visually evoked FV response in the PCA (neurovascular coupling), and the hypercapnia-induced FV response in the MCA (cerebral vasoreactivity). Visual evoked potential (VEP) and transcranial Doppler examinations were performed in 25 healthy adults before and after 24-h of SD. Cerebral vasoreactivity was measured by breath-holding test in left and right MCA. The visually evoked FV response was evaluated in left and right PCA. There was a tendency for increased resting mean FV in PCA (p = 0.08) and MCA (p = 0.07) after SD. Both the visually evoked FV response in the PCA and the hypercapnia-induced FV increase in the MCA were significantly lower after than before SD, however, no change in VEP amplitudes was found. Our study suggested that the impaired functional stimulation-evoked FV response after SD was not due to a reduced neuronal activation, but probably to a decreased vasodilatory response. Negative effects of SD on cerebral hemodynamics were also demonstrated by reduced cerebral vasoreactivity.

Characterising the protective vasodilatory effects of hypobaric hypoxia on the neurovascular coupling response

Neurovascular coupling (NVC) is the link between local neuronal activity and regional cerebral blood flow. High altitude (HA) ascent induces acute hypoxic vasodilation of the cerebral vasculature, with associated changes in CO2 and acid-base status. We aimed to characterise the effects of (a) acute removal of the HA-induced vasodilation and (b) rapid ascent to and residency at HA on NVC responses. In twelve healthy participants (7 M/5F), arterial blood gases and NVC were measured at baseline (1130 m) and on days two (<24 h at HA) and nine (post-acclimatisation) at 3800 m. Acute gas challenges were performed using end-tidal forcing, with (a) normoxia and isocapnic hypoxia at 1130 m and (b) poikilocapnic hypoxia and isocapnic hyperoxia on days two and nine at 3800 m. Posterior cerebral artery velocity (PCAv) was measured using transcranial Doppler ultrasound in each condition and time-point. NVC was assessed via a standardized 30 s intermittent strobe light visual stimulus (VS), and quantified as the peak and mean change from baseline in PCAv. No significant differences were observed for any NVC metric across all conditions and time points. Our results reveal remarkable stability of the NVC response following (a) acute removal of HA-induced hypoxic vasodilation and (b) rapid ascent to and residency at 3800 m.

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

PURPOSE

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.

METHODS

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.

RESULTS

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).

CONCLUSION

From the view of the NVC metrics, these findings provide new perspectives on the neuropathologic mechanisms and clinical treatment of SSNHL.

A New Perspective On Arterioectatic Spinal Angiopathy with a Reversible Pattern: Cause or Consequence?

OBJECTIVE

In 2022, arterioectatic spinal angiopathy (AESA) of childhood was reported as a fatal, progressive, multi-segment myelopathy associated with a unique form of non-inflammatory spinal angiopathy involving diffuse dilatation of the anterior spinal artery and cord congestion in children. In this study, we present four more cases of AESA, using early and long-term conventional imaging and flat detector computed tomography angiography (FDCTA) imaging to assess the probability of disease regression and prevent unnecessary interventions.

METHODS

We retrospectively reviewed the clinical and radiological findings of four patients with AESA seen in two neuroradiology departments between 2014 and 2023.

RESULTS

The study included three boys and one girl. Two of the boys were siblings. Although the clinical and radiological presentation in the early stages of the clinical course overlapped the definition of AESA, the clinical course was more benign in three of the cases. The clinical courses of the two siblings with monosegmental cord involvement and largely reversible radiological findings suggest that some of the features in the initial definition of the disease cannot be standardized for all patients. The siblings had a mutation of the NDUFS gene, which is involved in mitochondrial function and clinical-radiological reversibility in these patients.

CONCLUSION

Many mitochondrial diseases, such as this NDUFS mutation, present with myelopathy, and mitochondrial diseases can sometimes show spontaneous recovery. It is crucial to identify other genetic mutations or environmental factors that trigger the accompanying vascular ectatic findings in AESA in larger multicenter studies to prevent its potential lethal course and possible unnecessary surgical-endovascular interventions.

Challenges and Frontiers in Computational Metabolic Psychiatry

One of the primary challenges in metabolic psychiatry is that the disrupted brain functions that underlie psychiatric conditions arise from a complex set of downstream and feedback processes that span multiple spatiotemporal scales. Importantly, the same circuit can have multiple points of failure, each of which results in a different type of dysregulation, and thus elicits distinct cascades downstream that produce divergent signs and symptoms. Here, we illustrate this challenge by examining how subtle differences in circuit perturbations can lead to divergent clinical outcomes. We also discuss how computational models can perform the spatially heterogeneous integration and bridge in vitro and in vivo paradigms. By leveraging recent methodological advances and tools, computational models can integrate relevant processes across scales (e.g., tricarboxylic acid cycle, ion channel, neural microassembly, whole-brain macrocircuit) and across physiological systems (e.g., neural, endocrine, immune, vascular), providing a framework that can unite these mechanistic processes in a manner that goes beyond the conceptual and descriptive to the quantitative and generative. These hold the potential to sharpen our intuitions toward circuit-based models for personalized diagnostics and treatment.

Unveiling the Interplay: Neurovascular Coupling, Astrocytes and G Protein-Coupled Receptors in Alzheimer's Disease

Astrocytes are a type of glial cell that are involved in actively modulating synaptic plasticity, neurotransmitter homeostasis, and neuroinflammatory responses. More importantly, they coordinate neuronal activity and cerebral blood flow (CBF) in what is known as neurovascular coupling (NVC). NVC is an essential mechanism that maintains the high energy demand the brain requires by supplying continuous and rapid supply of oxygen and nutrients through CBF. Impairment in NVC is one of the key events that triggers a spiral of occurrences that lead to the clinical advancement of Alzheimer's disease (AD). It is yet to be determined what the molecular manifestations of NVC impairment relate to; nonetheless, it is believed that alterations in G protein-coupled receptors (GPCRs) are responsible for exacerbating these effects. In this review, we summarize the current evidence supporting the involvement of GPCRs on astrocytes in NVC and the pathophysiology of AD. Additionally, we propose potential research directions to further elucidate the underlying mechanisms and evaluate the feasibility of targeting specific GPCRs as a therapeutic strategy to correct brain blood flow and memory impairments associated with AD.

On the journey to measure cognitive expertise: What can functional imaging tell us?

BACKGROUND

Experience level correlates with motor cortex and supplementary motor area activation during laparoscopy. Whether brain activation patterns correlate with cognitive surgical task expertise is unknown. We compared the functional neuroimaging responses during simulated operative dictation-a cognitive surgical task-by experience level.

STUDY DESIGN

Junior (postgraduate years 1-3) and senior (postgraduate years 4-5) residents and attendings were recruited over 1 year. After a baseline rest period, participants were asked to dictate a simulated operative note for an open inguinal hernia repair with mesh. Functional near-infrared spectroscopy data were recorded from the prefrontal, sensorimotor, and occipital brain areas. The hemodynamic response based on changes in oxyhemoglobin and deoxyhemoglobin concentrations during the task relative to the pre-task baseline for each participant were calculated. Group-level differences in oxyhemoglobin were evaluated using a general linear model.

RESULTS

Thirty participants, 10 from each of the 3 experience levels, were recruited. In the left prefrontal cortex, senior activation (-182) was stronger than both junior (14) and attending (27) activation (P < .001). In the left premotor cortex, senior activation (-147) was stronger than both junior (-52) and attending (15) activation (P = .008). In the left parietal cortex, senior activation (-255) was stronger than both junior (-41) and attending (12) activation (P < .001).

CONCLUSION

Functional neuroimaging responses during the cognitive task of simulated operative dictation differ by skill level. This study represents the first brain imaging analysis of cognitive function connecting mental imagery, brain activation, and a cognitive surgical task linked to previously performed motor tasks. Functional neuroimaging may act as a nonbiased assessment tool of cognitive skill.

Hypocapnia, eucapnia, and hypercapnia during "Where's Waldo" search paradigms: Neurovascular coupling across the cardiac cycle and biological sexes

This investigation explored the impact of partial pressure of end-tidal carbon dioxide (PETCO2) alterations on temporal neurovascular coupling (NVC) responses across the cardiac cycle and the influence of biological sex via a complex visual scene-search task ("Where's Waldo?"). 10 females and 10 males completed five puzzles, each with 40 seconds of eyes open and 20 seconds of eyes closed, under PETCO2 clamped at ∼40 mmHg (eucapnia), ∼55 mmHg (hypercapnia), and ∼25 mmHg (hypocapnia). Cerebral blood velocity (CBv) in the middle and posterior cerebral arteries (MCAv, PCAv) were measured via Transcranial Doppler ultrasound. Linear mixed-effects models with participants as a random effect analyzed NVC metrics, including baseline and peak CBv, relative increase, and area-under-the-curve (AUC30). During hypercapnic trials, reductions in PCAv and MCAv AUC30 were noted across the cardiac cycle (all p < 0.001). Hypocapnic PCAv AUC30 was reduced (all p < 0.012), as was systolic MCAv AUC30 (p = 0.003). Females displayed greater baseline PCA diastole (p = 0.048). No other biological sex differences were observed across conditions in baseline (all p > 0.050), peak (all p > 0.054), relative increase (all p > 0.511), and AUC30 metrics (all p > 0.514). Despite differences in responses to hypercapnic and hypocapnic stimuli, NVC responses to complex visual tasks remain robust, across the physiological CO2 range.

Physio-fUS: a tissue-motion based method for heart and breathing rate assessment in neurofunctional ultrasound imaging

BACKGROUND

Recent studies have shown growing evidence that brain function is closely synchronised with global physiological parameters. Heart rate is linked to various cognitive processes and a strong correlation between neuronal activity and breathing has been demonstrated. These findings highlight the significance of monitoring these key physiological parameters during neuroimaging as they provide valuable insights into the overall brain function. Today, in neuroimaging, assessing these parameters requires additional cumbersome devices or implanted electrodes. Here we demonstrate that ultrasonic neurofunctional imaging data alone is sufficient to extract these parameters.

METHODS

In this work, we performed ultrafast ultrasound imaging in male rodents and human neonates, and we extracted heart and breathing rates from local tissue motion assessed by raw ultrasound data processing. Such "Physio-fUS" automatically selects two specific and optimal brain regions with pulsatile tissue signals to monitor such parameters.

FINDINGS

We validated the correspondence of these periodic signals with heart and breathing rates assessed using gold-standard electrodes in anaesthetised rodents. We extracted heart and breathing rates in sleeping rats and heart rate in rats moving freely in an arena. We also validated Physio-fUS imaging in sleeping human newborns using conventional ECG.

INTERPRETATION

We show the potential of fUS imaging as an integrative tool for simultaneously monitoring physiological parameters during neurofunctional imaging. Beyond the technological improvement, it could enhance our understanding of the link between breathing, heart rate and neurovascular activity in preclinical research and clinical functional ultrasound imaging.

FUNDING

This study was supported by the European Research Council under the European Union's Seventh Framework Program (FP/2007-2013)/ERC Grant Agreement n°311025 and by the Fondation Bettencourt-Schueller under the program "Physics for Medicine".

Hyperspectral imaging in neurosurgery: a review of systems, computational methods, and clinical applications

Significance

Accurate identification between pathologic (e.g., tumors) and healthy brain tissue is a critical need in neurosurgery. However, conventional surgical adjuncts have significant limitations toward achieving this goal (e.g., image guidance based on pre-operative imaging becomes inaccurate up to 3 cm as surgery proceeds). Hyperspectral imaging (HSI) has emerged as a potential powerful surgical adjunct to enable surgeons to accurately distinguish pathologic from normal tissues.

Aim

We review HSI techniques in neurosurgery; categorize, explain, and summarize their technical and clinical details; and present some promising directions for future work.

Approach

We performed a literature search on HSI methods in neurosurgery focusing on their hardware and implementation details; classification, estimation, and band selection methods; publicly available labeled and unlabeled data; image processing and augmented reality visualization systems; and clinical study conclusions.

Results

We present a detailed review of HSI results in neurosurgery with a discussion of over 25 imaging systems, 45 clinical studies, and 60 computational methods. We first provide a short overview of HSI and the main branches of neurosurgery. Then, we describe in detail the imaging systems, computational methods, and clinical results for HSI using reflectance or fluorescence. Clinical implementations of HSI yield promising results in estimating perfusion and mapping brain function, classifying tumors and healthy tissues (e.g., in fluorescence-guided tumor surgery, detecting infiltrating margins not visible with conventional systems), and detecting epileptogenic regions. Finally, we discuss the advantages and disadvantages of HSI approaches and interesting research directions as a means to encourage future development.

Conclusions

We describe a number of HSI applications across every major branch of neurosurgery. We believe these results demonstrate the potential of HSI as a powerful neurosurgical adjunct as more work continues to enable rapid acquisition with smaller footprints, greater spectral and spatial resolutions, and improved detection.

Speech-in-noise hearing impairment is associated with increased risk of Parkinson's: A UK biobank analysis

BACKGROUND

Hearing impairment is implicated as a risk factor for Parkinson's disease (Parkinson's) incidence, with evidence suggesting that clinically diagnosed hearing loss increases Parkinson's risk 1.5-1.6 fold over 2-5 years follow up. However, the evidence is not unanimous with additional studies observing that self-reported hearing capabilities do not significantly influence Parkinson's incidence. Thus, additional cohort analyses that draw on alternative auditory measures are required to further corroborate the link between Parkinson's and hearing impairment.

OBJECTIVES

To determine whether hearing impairment, estimated using a speech-in-noise test (the Digit Triplet Test, DTT), is a risk factor for Parkinson's incidence.

METHODS

This was a pre-registered prospective cohort study using data from the UK Biobank. Data pertaining to 159,395 individuals, who underwent DTT testing and were free from Parkinson's at the point of assessment, were analysed. A Cox Proportional Hazard model, controlling for age, sex and educational attainment was conducted.

RESULTS

During a median follow up of 14.24 years, 810 cases of probable Parkinson's were observed. The risk of incident Parkinson's increased with baseline hearing impairment [hazard ratio: 1.57 (95%CI: 1.018, 2.435; P = .041)], indicating 57 % increase in risk for every 10 dB increase in speech-reception threshold (SRT). However, when hearing impairment was categorised in accordance with UK Biobank SRT norms neither 'Insufficient' nor 'Poor' hearing significantly influenced Parkinson's risk compared to 'Normal' hearing.

CONCLUSIONS

The congruence of these findings with prior research further supports the existence of a relationship between hearing impairment and Parkinson's incidence.

Cerebral blood flow differences in cognitive disengagement syndrome and attention deficit hyperactivity disorder: Doppler ultrasonography findings

OBJECTIVE

The present study aims to investigate potential differences in cerebral blood flow between children with Cognitive Disengagement Syndrome (CDS) and those with Attention Deficit Hyperactivity Disorder (ADHD) using Doppler ultrasound.

METHODS

In this single-center prospective study, we included 24 cases in the ADHD group with CDS symptoms, 29 cases in the ADHD group without CDS symptoms and, 26 children in the healthy controls. The children ranged in age from 6 to 15. Participants were evaluated by diagnostic interviews and standardized measures. Doppler ultrasound was performed to measure peak systolic velocity and blood flow volume (BFV) in the internal carotid (ICA) and vertebral arteries for each participant.

RESULTS

The right ICA and total ICA BFVs were significantly lower in the CDS group compared to the ADHD and control groups (p = 0.007 and p = 0.003, respectively). In addition, there was a weak negative correlation between right ICA BFV and CDS scores, suggesting a possible link between reduced cerebral blood flow and CDS symptom severity.

CONCLUSION

This study provides a noteworthy starting point for research on the neurovascular basis of CDS. Our findings indicated significant differences in cerebral blood flow between CDS and ADHD, supporting the idea that CDS is a unique attentional disorder with distinct neurobiological characteristics from ADHD.

New evidence for baroreflex and respiratory chemoreflex-mediated cerebral sympathetic activation in humans

The brain is highly innervated by sympathetic nerve fibers; however, their physiological purpose is poorly understood. We hypothesized that unilateral cerebral norepinephrine (NE) spillover, an index of cerebral sympathetic nerve activity (SNA), would be elevated when engaging the baroreflex [via lower-body negative pressure (LBNP; -20 and -40 Torr)] and respiratory chemoreflexes [via carbon dioxide (CO2) administration (+8 Torr)], independently and in combination. Twelve young and healthy participants (five females) underwent simultaneous blood sampling from the right radial artery and internal jugular vein. Tritiated NE was infused through the participants' right forearm vein. Right internal jugular vein and internal carotid artery blood flow were measured using duplex ultrasound. Unilateral cerebral NE spillover remained unchanged when only LBNP was applied (P = 0.29) but increased with hypercapnia (P = 0.035) and -40 Torr LBNP + CO2 (P < 0.01). There were no changes in total NE spillover during the LBNP and LBNP + CO2 trials (both P = 0.66), nor during CO2 alone (P = 0.13). No correlations were present between the increase in unilateral cerebral NE spillover during -40 Torr LBNP + CO2 and reductions in internal carotid artery blood flow (P = 0.56). These results indicate that baroreflex and respiratory chemoreflex stressors elevate cerebral SNA; however, the observed cerebral sympathetic activation has no impact on blood flow regulation in the internal carotid artery.NEW & NOTEWORTHY The results of the current study suggest that baroreflex and respiratory chemoreflex stressors elevate cerebral sympathetic nervous activity, quantified using the brain norepinephrine spillover method. However, the observed cerebral sympathetic activation has no impact on blood flow regulation in the internal carotid artery.

Neural Activity Alterations and Their Association With Neurotransmitter and Genetic Profiles in Schizophrenia: Evidence From Clinical Patients and Unaffected Relatives

BACKGROUND

The pattern of abnormal resting-state brain function has been documented in schizophrenia (SCZ). However, as of yet, it remains unclear whether this pattern is of genetic predisposition or related to the illness itself.

METHODS

A systematical meta-analysis was performed to identify resting-state functional differences in probands and their high-risk first-degree relatives of schizophrenia (FDRs-SCZ) using Seed-based d Mapping software. Subsequently, spatial associations between postmortem gene expression and neurotransmitters distribution data and neural activity alterations were conducted to uncover neural mechanisms underlaying FDRs-SCZ and SCZ from a multidimensional perspective.

RESULTS

A total of 13 studies comprising 503 FDRs-SCZ and 605 healthy controls (HCs) and 129 studies comprising 6506 patients with SCZ and 6982 HCs were included. Compared to HCs, FDRs-SCZ displayed increased spontaneous functional activity in the bilateral anterior cingulate cortex/medial prefrontal cortex (ACC/mPFC); patients with SCZ showed decreased spontaneous functional activity in the bilateral ACC/mPFC, bilateral postcentral gyrus, and right middle temporal gyrus as well as increased spontaneous functional activity in the bilateral striatum. The altered functional activity in FDRs-SCZ and SCZ shared similar spatial associations with genes enriched in potassium ion transmembrane transport, channel activity, and complex. The FDRs-SCZ and SCZ-related brain functional patterns were additionally associated with dopaminergic, serotonergic, and cholinergic neurotransmitter distribution.

CONCLUSIONS

SCZ-related resting-state functional, neuroimaging transcriptomes, and neurotransmitters abnormalities may exist in high-risk unaffected FDRs-SCZ, rather than just in overt SCZ. The study extended the evidence that altered brain function, along with their spatial correlations to genetics and neurotransmitter systems, may associate with genetic vulnerability for SCZ.

State-dependent neurovascular modulation induced by transcranial ultrasound stimulation

Previous studies reported baseline state-dependent effects on neural and hemodynamic responses to transcranial ultrasound stimulation. However, due to neurovascular coupling, neither neural nor hemodynamic baseline alone can fully explain the ultrasound-induced responses. In this study, using a general linear model, we aimed to investigate the roles of both neural and hemodynamic baseline status as well as their interactions in ultrasound-induced responses. Thirty Sprague-Dawley rats were randomly assigned to Hypoxia, Hyperoxia, and Normoxia groups. The baseline states were altered by changing the oxygen concentrations. Micro-electrode and laser speckle contrast imaging were used to record local field potentials and cerebral blood flow during resting, before, and after ultrasound stimulation, respectively. We found that baseline neural activity played a positive role in neural response (Coefficient = 0.634, t = 1.748, p = 0.096,η p 2 = 0.133), but a negative role in hemodynamic response (Coefficient = - 0.060, t = - 1.996, p = 0.060,η p 2 = 0.166). Baseline hemodynamic activity also had a significantly negative correlation with the hemodynamic response (Coefficient = - 0.760, t = - 3.947, p < 0.001,η p 2 = 0.438). This study enriched our understanding of state-dependent effects underlying the neurovascular activation by ultrasound stimulation.

Resting state BOLD-perfusion coupling patterns using multiband multi-echo pseudo-continuous arterial spin label imaging

The alteration of neurovascular coupling (NVC), where acute localized blood flow increases following neural activity, plays a key role in several neurovascular processes including aging and neurodegeneration. While not equivalent to NVC, the coupling between simultaneously measured cerebral blood flow (CBF) with arterial spin labeling (ASL) and blood oxygenation dependent (BOLD) signals, can also be affected. Moreover, the acquisition of BOLD data allows the assessment of resting state (RS) fMRI metrics. In this study a multiband, multi-echo (MBME) pseudo-continuous ASL (pCASL) sequence was used to collect simultaneous BOLD and ASL data in a group of healthy control subjects, and the patterns of BOLD-CBF coupling were evaluated. Coupling was also correlated with the BOLD RS measures. The variability, reproducibility, and reliability of the metrics were also computed in a multi-session subgroup. Areas of higher coupling were observed in the visual, motor, parietal, and frontal cortices and corresponded to major brain networks. Areas of significant correlation between coupling and BOLD RS measures corresponded to areas of heightened coupling. Higher variability and lower reliability were found for coupling metrics compared to BOLD RS metrics. These results indicate BOLD-CBF coupling metrics may be useful for studying neurovascular physiology.

The Crucial Role of the Blood-Brain Barrier in Neurodegenerative Diseases: Mechanisms of Disruption and Therapeutic Implications

The blood-brain barrier (BBB) is a crucial structure that maintains brain homeostasis by regulating the entry of molecules and cells from the bloodstream into the central nervous system (CNS). Neurodegenerative diseases such as Alzheimer's and Parkinson's disease, as well as ischemic stroke, compromise the integrity of the BBB. This leads to increased permeability and the infiltration of harmful substances, thereby accelerating neurodegeneration. In this review, we explore the mechanisms underlying BBB disruption, including oxidative stress, neuroinflammation, vascular dysfunction, and the loss of tight junction integrity, in patients with neurodegenerative diseases. We discuss how BBB breakdown contributes to neuroinflammation, neurotoxicity, and the abnormal accumulation of pathological proteins, all of which exacerbate neuronal damage and facilitate disease progression. Furthermore, we discuss potential therapeutic strategies aimed at preserving or restoring BBB function, such as anti-inflammatory treatments, antioxidant therapies, and approaches to enhance tight junction integrity. Given the central role of the BBB in neurodegeneration, maintaining its integrity represents a promising therapeutic approach to slow or prevent the progression of neurodegenerative diseases.

A multimodal neuroimaging study of cerebrovascular regulation: protocols and insights of combining electroencephalography, functional near-infrared spectroscopy, transcranial Doppler ultrasound, and physiological parameters

Objective. The current paper describes the creation of a simultaneous trimodal neuroimaging protocol. The authors detail their methodological design for a subsequent large-scale study, demonstrate the ability to obtain the expected physiologically induced responses across cerebrovascular domains, and describe the pitfalls experienced when developing this approach.Approach. Electroencephalography (EEG), functional near-infrared spectroscopy (fNIRS), and transcranial Doppler ultrasound (TCD) were combined to provide an assessment of neuronal activity, microvascular oxygenation, and upstream artery velocity, respectively. Real-time blood pressure, capnography, and heart rate were quantified to control for the known confounding influence of cardiorespiratory variables. The EEG-fNIRS-TCD protocol was attached to a 21 year-old male who completed neurovascular coupling/functional hyperemia (finger tapping and 'Where's Waldo/Wally?'), dynamic cerebral autoregulation (squat-stand maneuvers), and cerebrovascular reactivity tasks (end-tidal clamping during hypocapnia/hypercapnia).Main results. In a pilot participant, the Waldo task produced robust hemodynamic responses within the occipital microvasculature and the posterior cerebral artery. A ∼90% decrease in alpha band power was seen in the occipital cortical region compared between the eyes closed and eyes opened protocol, compared to the frontal, central, and parietal regions (∼80% reduction). A modest increase in motor oxygenated hemoglobin was seen during the finger tapping task, with a harmonious alpha decrease of ∼15% across all cortical regions. No change in the middle or posterior cerebral arteries were noted during finger tapping. During cerebral autoregulatory challenges, sinusoidal oscillations were produced in hemodynamics at 0.05 and 0.10 Hz, while a decrease and increase in TCD and fNIRS metrics were elicited during hypocapnia and hypercapnia protocols, respectively.Significance. All neuroimaging modalities have their inherent limitations; however, these can be minimized by employing multimodal neuroimaging approaches. This EEG-fNIRS-TCD protocol enables a comprehensive assessment of cerebrovascular regulation across the association between electrical activity and cerebral hemodynamics during tasks with a mild degree of body and/or head movement.

Contralateral Neurovascular Coupling in Patients with Ischemic Stroke After Endovascular Thrombectomy

BACKGROUND

Neurovascular coupling (NVC) refers to the process of aligning cerebral blood flow with neuronal metabolic demand. This study explores the potential of contralateral NVC-linking neural electrical activity on the stroke side with cerebral blood flow velocity (CBFV) on the contralesional side-as a marker of physiological function of the brain. Our aim was to examine the association between contralateral NVC and neurological outcomes in patients with ischemic stroke following endovascular thrombectomy.

METHODS

We concurrently recorded the CBFVs of the middle cerebral arteries and electroencephalographic (EEG) signals of patients after endovascular thrombectomy. We employed phase-amplitude cross-frequency coupling to quantify the contralateral coupling between EEG activity on the stroke side and CBFV on the contralesional side. Key neurological outcomes were measured, including changes in National Institute of Health Stroke Scale (NIHSS) scores, infarct volume progression over 7 days, and modified Rankin Scale scores at 90 days.

RESULTS

A total of 52 study participants were enrolled in our study (mean age 61.5 ± 10.4 years; 90.4% male; median preprocedural NIHSS score 14 [interquartile range 10-17]). We successfully computed contralateral NVC in 48 study participants. A significant association emerged between contralateral coupling and improvements in NIHSS scores over 7 days (theta band, P = 0.030) and in infarct volume progression (delta band, P = 0.001; theta band, P = 0.013). Stronger contralateral NVC in the delta and theta bands correlated with better outcomes at 90 days (adjusted odds ratio for delta 7.53 [95% confidence interval 1.13-50.30], P = 0.037; adjusted odds ratio for theta 6.36 [95% confidence interval 1.09-37.01], P = 0.039).

CONCLUSIONS

A better contralateral coupling between stroke-side EEG and contralesional CBFV is associated with favorable neurological outcomes, suggesting that contralateral NVC analysis may aid in assessing brain function after recanalization. Replication with a deeper understanding of the mechanisms is needed before clinical translation.

Label free, capillary-scale blood flow mapping in vivo reveals that low-intensity focused ultrasound evokes persistent dilation in cortical microvasculature

Non-invasive, low intensity focused ultrasound is an emerging neuromodulation technique that offers the potential for precision, personalized therapy. An increasing body of research has identified mechanosensitive ion channels that can be modulated by FUS and support acute electrical activity in neurons. However, neuromodulatory effects that persist from hours to days have also been reported. The brain's ability to provide blood flow to electrically active regions involves a multitude of non-neuronal cell types and signaling pathways in the cerebral vasculature; an open question is whether persistent effects can be attributed, at least partly, to vascular mechanisms. Using an in vivo optical approach, we found that microvasculature, and not larger vessels, exhibit significant persistent dilation following sonication without the use of microbubbles. This finding reveals a heretofore unseen aspect of the effects of FUS in vivo and indicates that concurrent changes in neurovascular function may partially underly persistent neuromodulatory effects.

Impact of acute sleep restriction on cerebrovascular reactivity and neurovascular coupling in young men and women

Chronic exposure to shortened sleep is associated with an increased risk of Alzheimer's disease and dementia. Previous studies show insufficient (e.g., poor or fragmented) sleep impairs cerebrovascular reactivity to metabolic stress and may have a detrimental effect on the link between cerebral blood flow (CBF) and neural activity (i.e., neurovascular coupling, NVC). The purpose of this study was to examine the effect of acute sleep restriction on CBF in response to a metabolic (carbon dioxide, CO2) and a cognitive stressor. We hypothesized sleep restriction (4-h time in bed) would attenuate CBF and NVC. Sixteen young adults (8 M/8 F, 28 ± 8 yr, 25 ± 3 kg/m2) completed two morning visits following a night of normal (7.38 ± 0.82 h) or restricted (4.27 ± 0.93 h, P < 0.001) sleep duration. Middle cerebral artery velocity (MCAv, transcranial Doppler ultrasound) was measured at rest and during 1) 5 min of carbogen air-breathing and 2) five trials consisting of a period of eyes closed (30 s), followed by eyes open (40 s) while being challenged with a validated visual paradigm (Where's Waldo). Baseline MCAv was unaffected by acute sleep restriction (control: 64 ± 14 cm/s; restricted 61 ± 13 cm/s; P = 0.412). MCAv increased with CO2; however, there was no effect of restricted sleep (P = 0.488). MCAv increased in response to visual stimulation; the peak NVC response was reduced from control following restricted sleep (control: 16 ± 12%; restricted: 9 ± 7%; P = 0.008). Despite no effect of acute sleep restriction on resting CBF or the response to CO2 in young men and women, NVC was attenuated following a night of shortened sleep. These data support an important role for sleep in NVC and may have implications for the development of neurodegenerative disease states, such as Alzheimer's and dementia.NEW & NOTEWORTHY Chronic exposure to shortened sleep is associated with an increased risk of Alzheimer's disease and dementia. We examined the effect of acute sleep restriction (4-h time in bed) on cerebral blood flow in response to a metabolic (carbon dioxide) and a cognitive stimulus. Despite no effect of acute sleep restriction on resting cerebral blood flow or the response to carbon dioxide in young men and women, neurovascular coupling was attenuated following a night of shortened sleep.

Trimodal brain imaging: A novel approach for simultaneous investigation of human brain function

While advancements have improved the extent to which individual brain imaging approaches capture information regarding spatial or temporal dynamics of brain activity, the connections between these aspects and their relation to psychological functioning remain only partially understood. Acquisition and integration across multiple brain imaging modalities allows for the possible clarification of these connections. The present review provides an overview of three complementary modalities - functional magnetic resonance imaging (fMRI), electroencephalography/event-related potentials (EEG/ERP), and event-related optical signals (EROS) - and discusses progress and considerations for each modality, along with a summary of a novel protocol for acquiring them simultaneously. Initial evidence points to the feasibility of acquiring and integrating multiple measures of brain function that allows for addressing questions in ways not otherwise possible using traditional approaches. Simultaneous trimodal brain imaging in humans provides new possibilities for clarifying spatiotemporal dynamics of brain activity and for identifying multifaceted associations with measures of individual differences and important health outcomes.

Response of capillaries and small arterioles to full-field flicker is not dependent on local ganglion cell thickness

To measure the influence of ganglion cell layer (GCL) thickness on the changes in size and red blood cell (RBC) flow in small retinal vessels evoked by full-field flicker. We used a dual-beam adaptive optics scanning laser ophthalmoscope to image 11 healthy young controls in two retinal areas with significantly different GCL thicknesses. All capillaries and arterioles of the superficial vascular plexus were responsive to the flicker stimulation. Average lumen dilation and RBC flow changes were greater in capillaries than in arterioles (vasodilation: 10.9%, 6.7%; RBC flow: 51%, 38%, respectively). No statistically significant differences regarding relative lumen diameter, RBC velocity, or RBC flow were found with respect to GCL thickness, or vessel size.

Brain neurovascular coupling in amyotrophic lateral sclerosis: Correlations with disease progression and cognitive impairment

BACKGROUND AND PURPOSE

'Neurovascular coupling' (NVC) alterations, assessing the interplay between local cerebral perfusion and neural activity within a given brain region or network, may reflect neurovascular unit impairment in amyotrophic lateral sclerosis (ALS). The aim was to explore NVC as a correlation between the functional connectivity and cerebral blood flow within the large-scale resting-state functional magnetic resonance imaging brain networks in a sample of ALS patients compared to healthy controls (HCs).

METHODS

Forty-eight ALS patients (30 males; mean age 60.64 ± 9.62 years) and 32 HC subjects (14 males; mean age 55.06 ± 16 years) were enrolled and underwent 3 T magnetic resonance imaging. ALS patients were screened by clinical and neuropsychological scales and were retrospectively classified as very fast progressors (VFPs), fast progressors and slow progressors (SPs).

RESULTS

Neurovascular coupling reduction within the default mode network (DMN) (p = 0.005) was revealed in ALS patients compared to HCs, observing, for this network, significant NVC differences between VFP and SP groups. Receiver operating characteristic curve analysis showed that impaired NVC in the DMN at baseline best discriminated VFPs and SPs (area under the curve 75%). Significant correlations were found between NVC and the executive (r = 0.40, p = 0.01), memory (r = 0.32, p = 0.04), visuospatial ability (r = 0.40, p = 0.01) and non-ALS-specific (r = 0.40, p = 0.01) subscores of the Edinburgh Cognitive and Behavioural ALS Screen.

CONCLUSIONS

The reduction of brain NVC in the DMN may reflect largely distributed abnormalities of the neurovascular unit. NVC alterations in the DMN could play a role in anticipating a faster clinical progression in ALS patients, aiding patient selection and monitoring during clinical trials.

Intra-subject test-retest reliability for auditory-evoked functional near-infrared spectroscopy responses: effects of systemic physiology correction

Significance

Functional near-infrared spectroscopy (fNIRS) is a valuable neuroimaging tool for non-invasively measuring hemodynamic changes in response to neural activity, particularly in auditory research. Although fNIRS shows strong test-retest reliability at the group level, individual-subject level reliability is often compromised by systemic noise.

Aim

We investigate how correcting for systemic-physiological signals affects reliability in single-subject fNIRS data.

Approach

fNIRS data were collected from one participant over 10 sessions during a passive auditory task. Using general linear modeling, six correction approaches were compared: no correction, physiology correction, short-channel correction, short-channel + physiology correction, short-channel + physiology + lag correction, and short-channel + tCCA correction.

Results

Intraclass correlation coefficient analysis revealed that physiology correction yielded the highest test-retest reliability score, whereas short-channel correction had the lowest. These results align with previous findings suggesting that global systemic artifacts bolster reliability, and regressing such artifacts enhances the clarity of the observed neuronal response, as supported by visual comparisons of raw and denoised signals.

Conclusions

We highlight the impact of correcting for extra-cerebral signals in single-subject auditory research and demonstrate that, while incorporating short channels in fNIRS data collection may reduce reliability, it offers a more accurate representation of the neuronal response.

Exercise as a Therapeutic Strategy to Improve Cerebrovascular Function and Cognition in Breast Cancer Survivors: A Scoping Review

Breast cancer is the most diagnosed cancer globally. While the breast cancer prevalence continues to rise, so too do patient survival rates, thus resulting in a large survivor population. Up to 75% of this population report experiencing cancer-related cognitive impairment during their cancer journey, thus reducing their quality of survivorship. This review systematically evaluates the effect of physical activity and exercise training on cerebrovascular function and cognition in breast cancer survivors. Cross-sectional, intervention or observational studies that examined the effect of acute or chronic exercise training or physical activity levels on cerebrovascular function and cognition in female breast cancer survivors were searched for systematically. The 11 included studies were tabulated and described narratively. The included studies primarily focused on aerobic exercise training, while only four studies investigated the effect of resistance exercise training or concurrent training on cerebrovascular function and/or cognition in breast cancer survivors. Collectively, these studies provide preliminary evidence supporting the positive effect of exercise training on cerebrovascular function and cognition in breast cancer survivors, irrespective of their age, stage of breast cancer and treatment regimen. However, more research is required to comprehensively evaluate the effect of exercise training on cerebrovascular function and cognition in breast cancer survivors and the mechanisms leading to these potential improvements.

The Cardiac Output-Cerebral Blood Flow Relationship Is Abnormal in Most Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients with a Normal Heart Rate and Blood Pressure Response During a Tilt Test

INTRODUCTION

Orthostatic intolerance is highly prevalent in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and is caused by an abnormal reduction in cerebral blood flow (CBF). In healthy controls (HCs), the regulation of CBF is complex and cardiac output (CO) is an important determinant of CBF: a review showed that a 30% reduction in CO results in a 10% reduction in CBF. In previous and separate ME/CFS studies, we showed that CO and CBF decreased to a similar extent during tilt testing.

THE AIM OF THE STUDY

to test the relationship between CBF and CO, which seems to be abnormal in ME/CFS patients and is different from that in HCs.

METHODS

In this retrospective study we analyzed this relationship in a large group of patients. To compare the patient data with those of HCs, we focused on patients with a normal heart rate (HR) and blood pressure (BP) response to upright tilt. Also, the influence of clinical data was analyzed. A total of 534 ME/CFS patients and 49 HCs underwent tilt testing with measurements of HR, BP, CBF, CO, and end-tidal PCO2. To measure CBF, extracranial Doppler flow velocity and vessel diameters were obtained using a GE echo system. The same device was used to measure suprasternal aortic flow velocities. End-tidal PCO2 was recorded using a Nonin Lifesense device.

RESULTS

In 46 (9%) patients, CO and CBF changes were in the normal range for HCs, and in 488 (91%) an abnormal CO and CBF reduction was found. In patients with abnormal CO and CBF reductions, the slope of the regression line of CO versus CBF reduction was almost 1. The multiple regression analysis of the latter group showed that the CO reduction for the most part predicted the CBF reduction, with a limited role for the PETCO2 reduction.

CONCLUSIONS

Two different patient groups with a normal HR and BP response during the tilt were identified: those with a CO and CBF in the normal range for HCs and those with an abnormal CO and CBF reduction during the tilt (91% of patients). In the latter group of patients, an almost 1:1 relationship between the CO and CBF reduction suggests the absence of compensatory vasodilation in the cerebral vasculature. This might indicate endothelial dysfunction in most ME/CFS patients and may have clinical and therapeutic implications.

Evaluation of Neurovascular Coupling in Early-Onset and Late-Onset Epilepsy of Unknown Etiology

BACKGROUND

Previous studies have shown neurovascular coupling (NVC) dysfunction in epilepsy, suggesting its role in the pathological mechanisms. However, it remains unclear whether NVC abnormalities exist in epilepsy of unknown etiology (EU).

PURPOSE

To integrate multiparametric MRI to assess NVC and its relationship with cognition in early-onset and late-onset EU patients.

STUDY TYPE

Prospective.

POPULATION

Ninety-six EU patients (46 early-onset, M/F = 20/26; 50 late-onset, M/F = 29/21) and 60 healthy controls (HCs, M/F = 25/35).

FIELD STRENGTH/SEQUENCE

3.0 T, resting-state gradient echo-planar imaging, pseudo-continuous arterial spin labeling (pc-ASL), and T1-weighted brain volume sequence.

ASSESSMENT

Functional MRI data were analyzed to assess intrinsic brain activity including amplitude of low-frequency fluctuations (ALFF), fractional ALFF (fALFF), regional homogeneity (ReHo), and functional connectivity strength (FCS), while pc-ASL provided cerebral blood flow (CBF) measurements. Coupling correlation coefficients and ratios of CBF to neural activity were calculated to evaluate global and regional NVC.

STATISTICAL TESTS

Two-sample t-test, Analysis of Variance, Kruskal-Wallis test, Chi-square test, Analysis of Covariance, family-wise error/Bonferroni correction, partial correlation analyses. Statistical significance was defined as P < 0.05.

RESULTS

Whole-brain analysis revealed increased ALFF values in both patient groups' left precentral and postcentral gyri. Both patient groups had lower global NVC coefficients than HCs, with reduced CBF-ALFF (0.28 vs. 0.30), CBF-fALFF (0.43 vs. 0.45), and CBF-ReHo (0.40 vs. 0.41) in early-onset patients, and lower CBF-fALFF (0.38 vs. 0.45) and CBF-ReHo (0.32 vs. 0.41) in late-onset patients. Regional analysis showed significantly decreased CBF/ALFF ratios in the left precentral and postcentral gyri (T = 3.85 to 5.33). Reduced global NVC in early-onset patients was significantly associated with poorer executive function (r = 0.323), while global coupling in late-onset patients was negatively correlated with disease duration (r = -0.348 to -0.426).

DATA CONCLUSION

This study showed abnormal global and regional NVC in both early-onset and late-onset EU patients, emphasizing the potential role of NVC in the pathophysiological mechanisms of EU.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 1.

Regional dynamic cerebral autoregulation across anterior and posterior circulatory territories: A detailed exploration and its clinical implications

Cerebral autoregulation (CA) is the mechanism that maintains stable cerebral blood flow (CBF) despite fluctuations in systemic blood pressure, crucial for brain homeostasis. Recent evidence highlights distinct regional variations in CA between the anterior (carotid) and posterior (vertebrobasilar) circulations. Non-invasive neuromonitoring techniques, such as transcranial Doppler, transfer function analysis, and near-infrared spectroscopy, facilitate the dynamic assessment of CBF and autoregulation. Studies indicate a robust autoregulatory capacity in the anterior circulation, characterized by rapid adjustments in vascular resistance. On the contrary, the posterior circulation, mainly supplied by the vertebral arteries, may have a lower autoregulatory capacity. in acute brain injuries such as intracerebral and subarachnoid hemorrhage, and traumatic brain injuries, dynamic CA can be significantly altered in the posterior circulation. Proposed physiological mechanisms of impaired CA in the posterior circulation include: (1) Decreased sympathetic innervation of the vasculature impairing compensatory vasoreactivity; (2) Endothelial dysfunction; (3) Increased cerebral metabolic rate of oxygen consumption within the visual cortex causing CBF-metabolism (i.e., neurovascular) uncoupling; and (4) Impaired blood-brain barrier integrity leading to impaired astrocytic mediated release of vasoactive substances (e.g. nitric oxide, potassium, and calcium ions). Furthermore, more research is needed on the effects of collateral circulation, as well as the circle of Willis variants, such as the fetal-type posterior cerebral artery, on dynamic CA. Improving our understanding of these mechanisms is crucial to improving the diagnosis, prognosis, and management of various cerebrovascular disorders.

Investigating the acute cognitive effects of dietary compounds using fNIRS: methodological limitations and perspectives for research targeting healthy adults

The brain's response to cognitive demands hinges on sufficient blood flow, with changes in brain hemodynamics serving as a reflection of this process. Certain bioactive compounds found in our diet, such as caffeine, polyphenols, and nitrate, can acutely impact brain hemodynamics through diverse neural, vasoactive, and metabolic mechanisms. Functional Near-Infrared Spectroscopy (fNIRS) offers a non-invasive and real-time method to investigate these effects. Despite their potential, fNIRS studies investigating the acute impacts of bioactive compounds on cognition face methodological gaps, especially in controlling confounding factors. Given the impact of these confounding effects, which can be significant due to the relatively limited sample size of such studies, there is a need to refine the methodologies employed. This review proposes recommendations to enhance current methodologies in the research field, focusing on key aspects of the data collection phase, including research design, experimental paradigms, and participant demographics, and their integration into the analysis phase. Ultimately, it seeks to advance our understanding of the effects of bioactive compounds on cognitive functions to contribute to the development of targeted nutritional interventions for improved brain health.

Integrated Feedforward and Feedback Mechanisms in Neurovascular Coupling

Neurovascular coupling (NVC) is the mechanism that drives the neurovascular response to neural activation, and NVC dysfunction has been implicated in various neurologic diseases. NVC is driven by (1) nonmetabolic feedforward mechanisms that are mediated by various signaling pathways and (2) metabolic feedback mechanisms that involve metabolic factors. However, the interplay between these feedback and feedforward mechanisms remains unresolved. We propose that feedforward mechanisms normally drive a swift, neural activation-induced regional cerebral blood flow (rCBF) overshoot, which floods the tissue beds, leading to local hypocapnia and hyperoxia. The feedback mechanisms are triggered by the resultant hypocapnia (not hyperoxia), which causes cerebral vasoconstriction in the neurovascular unit that counterbalances the rCBF overshoot and returns rCBF to a level that matches the metabolic activity. If feedforward mechanisms function improperly (eg, in a disease state), the rCBF overshoot, tissue-bed flooding, and local hypocapnia fail to occur or occur on a smaller scale. Consequently, the neural activation-related increase in metabolic activity results in local hypercapnia and hypoxia, both of which drive cerebral vasodilation and increase rCBF. Thus, feedback mechanisms ensure the brain milieu's stability when feedforward mechanisms are impaired. Our proposal integrates the feedforward and feedback mechanisms underlying NVC and suggests that these 2 mechanisms work like a fail-safe system, to a certain degree. We also discussed the difference between NVC and cerebral metabolic rate-CBF coupling and the clinical implications of our proposed framework.

Combination of rs-fMRI, QSM, and ASL Reveals the Cerebral Neurovascular Coupling Dysfunction Is Associated With Cognitive Decline in Patients With Chronic Kidney Disease

BACKGROUND

Neurovascular coupling (NVC) reflects the close connection between neural activity and cerebral blood flow (CBF) responses, providing new insights to explore the neuropathological mechanisms of various diseases. Non-dialysis patients with chronic kidney disease (CKD) exhibit cognitive decline, but the underlying pathological mechanisms are unclear.

METHODS

The prospective study involved 53 patients with stage 1-3a CKD (CKD1-3a), 78 patients with stage 3b-5 CKD (CKD3b-5), and 52 healthy controls (HC). Our investigation involved voxel-based assessments of both global and regional BOLD signal characteristics. Additionally, we explored the correlations between neuroimaging indices, Montreal Cognitive Assessment (MoCA) scores, and clinical laboratory findings.

RESULTS

Compared to HC, the CKD3b-5 and CKD1-3a groups exhibited lower ALLF and ReHo in the default mode network (DMN), higher CBF in bilateral hippocampus (HIP), higher susceptibility values in bilateral caudate nucleus (CAU) and putamen (PUT), and lower susceptibility values in bilateral HIP. At the global level, the coupling coefficients were lower in CKD1-3a and CKD3b-5 groups than in HC. At the ROI level, the CBF-ALFF and CBF-ReHo coupling in HIP and basal ganglia regions were lower in CKD3b-5 groups than in the CKD1-3a group. Most importantly, susceptibility-ALFF in ANG.R may mediate the effects of phosphorus on cognitive decompensation in patients with CKD1-3a.

CONCLUSIONS

Non-dialysis patients with CKD exhibit abnormal NCV, which is associated with the cognitive decline. Specifically, the susceptibility-ALFF may serve as a valuable biomarker for early assessment of cognitive decline in CKD, offering insights into the pathogenesis of cognitive decline in CKD.

Muscular strength, endothelial function and cognitive disorders: state of the art

In recent years, the ageing population has increasingly grown. This process carries a range of pathophysiological changes involving alterations in the skeletal muscle, vascular endothelium and brain function, becoming an important risk factor for developing cognitive disorders and cardiovascular diseases. With ageing, there is a decrease in muscle mass and muscle strength, and a relationship between muscle strength decrease and cognitive decline has been shown. Lower handgrip strength has been linked to memory impairment, lower global cognitive function, decreased attention and reduced visuospatial abilities in the elderly, but understanding of the underlying mechanisms that explain the link between altered skeletal muscle function and structure, endothelial dysfunction, and the role of endothelial dysfunction in the onset of cognitive disorders has been scarcely explored. This review aims to detail the cellular and molecular mechanisms by which the progressive changes associated with ageing can alter healthy skeletal muscle and endothelial function, creating an environment of oxidative stress, inflammation and mitochondrial dysfunction. These changes can lead to reduced muscle strength, and the secretion of detrimental endothelial factors, resulting in endothelial dysfunction, blood-brain barrier disruption, and damage to neurons and microglia, ultimately accelerating the onset of cognitive disorders in the elderly. In addition, we aimed to describe the mechanisms that potentially explain how preserving muscular function with resistance training could prevent brain function deterioration, including the production of different factors that allow an improved endothelial function, haemodynamic parameters and brain plasticity, ultimately delaying the onset of cognitive impairment and chronic diseases.

Reduced neurovascular coupling is associated with increased cardiovascular risk without established cerebrovascular disease: A cross-sectional analysis in UK biobank

Mid-life vascular risk factors predict late-life cerebrovascular diseases and poor global brain health. Although endothelial dysfunction is hypothesized to contribute to this process, evidence of impaired neurovascular function in early stages remains limited. In this cross-sectional study of 31,934 middle-aged individuals from UK Biobank without established cerebrovascular disease, the overall 10-year risk of cardiovascular events was associated with reduced neurovascular coupling (p < 2 × 10-16) during a visual task with functional MRI, including in participants with no clinically apparent brain injury on MRI. Diabetes, smoking, waist-hip ratio, and hypertension were each strongly associated with decreased neurovascular coupling with the strongest relationships for diabetes and smoking, whilst in older adults there was an inverted U-shaped relationship with DBP, peaking at 70-80 mmHg DBP. These findings indicate that mid-life vascular risk factors are associated with impaired cerebral endothelial-dependent neurovascular function in the absence of overt brain injury. Neurovascular dysfunction, measured by neurovascular coupling, may play a role in the development of late-life cerebrovascular disease, underscoring the need for further longitudinal studies to explore its potential as a mediator of long-term cerebrovascular risk.

Comparing structure-function relationships in brain networks using EEG and fNIRS

Identifying relationships between structural and functional networks is crucial for understanding the large-scale organization of the human brain. The potential contribution of emerging techniques like functional near-infrared spectroscopy to investigate the structure-functional relationship has yet to be explored. In our study, using simultaneous Electroencephalography (EEG) and Functional near-infrared spectroscopy (fNIRS) recordings from 18 subjects, we characterize global and local structure-function coupling using source-reconstructed EEG and fNIRS signals in both resting state and motor imagery tasks, as this relationship during task periods remains underexplored. Employing the mathematical framework of graph signal processing, we investigate how this relationship varies across electrical and hemodynamic networks and different brain states. Results show that fNIRS structure-function coupling resembles slower-frequency EEG coupling at rest, with variations across brain states and oscillations. Locally, the relationship is heterogeneous, with greater coupling in the sensory cortex and increased decoupling in the association cortex, following the unimodal to transmodal gradient. Discrepancies between EEG and fNIRS are noted, particularly in the frontoparietal network. Cross-band representations of neural activity revealed lower correspondence between electrical and hemodynamic activity in the transmodal cortex, irrespective of brain state while showing specificity for the somatomotor network during a motor imagery task. Overall, these findings initiate a multimodal comprehension of structure-function relationship and brain organization when using affordable functional brain imaging.

Quantifying neurovascular coupling through a concurrent assessment of arterial, capillary, and neuronal activation in humans: A multimodal EEG-fNIRS-TCD investigation

BACKGROUND

This study explored a novel multimodal neuroimaging approach to assess neurovascular coupling (NVC) in humans using electroencephalography (EEG), functional near-infrared spectroscopy (fNIRS), and transcranial Doppler ultrasound (TCD).

METHODS

Fifteen participants (nine females; age 19-32) completed concurrent EEG-fNIRS-TCD imaging during motor (finger tapping) and visual ("Where's Waldo?") tasks, with synchronized monitoring of blood pressure, capnography, and heart rate. fNIRS assessed microvascular oxygenation within the frontal, motor, parietal, and occipital cortices, while the middle and posterior cerebral arteries (MCA/PCA) were insonated using TCD. A 16-channel EEG set-up was placed according to the 10-20 system. Wilcoxon signed-rank tests were used to compare physiological responses between the active and resting phases of the tasks, while cross-correlations with zero legs compared cerebral and systemic hemodynamic responses across both tasks.

RESULTS

Time-frequency analysis demonstrated a reduction in alpha and low beta band power in electrodes C3/C4 during finger tapping (p<0.045) and all electrodes during the Waldo task (all p<0.001). During Waldo, cross-correlation analysis demonstrated the change in oxygenated hemoglobin and cerebral blood velocity had a moderate-to-strong negative correlation with systemic physiological influences, highlighting the measured change resulted from neuronal input. Deoxygenated hemoglobin displayed the greatest negative cross-correlation with the MCA/PCA within the motor cortices and visual during the motor and visual tasks, respectively (range:0.54, -0.82).

CONCLUSIONS

This investigation demonstrated the feasibility of the proposed EEG-fNIRS-TCD response to comprehensively assess the NVC response within human, specifically quantifying the real-time temporal synchrony between neuronal activation (EEG), microvascular oxygenation changes (fNIRS), and conduit artery velocity alterations (TCD).

Creative music therapy in preterm infants effects cerebrovascular oxygenation and perfusion

Creative music therapy (CMT) has been shown to promote the development of brain function and structure in preterm infants. We aimed to investigate the effect of CMT on cerebral oxygenation and perfusion to examine how the brain reacts to CMT. Absolute levels of cerebrovascular oxygen saturation (StO2) were measured in clinically stable preterm-born neonates (n = 20, gestational age: ≥30 weeks and < 37 weeks) using two near-infrared spectroscopy (NIRS)-based tissue oximeters over the right prefrontal cortex and left auditory cortex. We applied the systemic physiology augmented functional NIRS approach. Each CMT session lasted 55 min and involved 9 intervals, including two 10-minute intervals during which the music therapist hummed and held the neonate. We found that CMT-induced changes in cerebrovascular StO2, perfusion and systemic physiology (i) could be classified into two groups (group 1: increase in StO2 during the first singing interval, group 2: decrease in StO2), (ii) differed in female neonates compared to male neonates, and (iii) correlated with individual blood haematocrit levels. Our exploratory study (i) demonstrates the impact of CMT on the neonate's physiology and (ii) highlights the need to analyze functional NIRS measurements in neonates separately according to their response pattern to avoid erroneous conclusions, e.g. when only the group average of the signal change is determined.

Psychedelic 5-HT2A receptor agonism: neuronal signatures and altered neurovascular coupling

Psychedelics hold therapeutic promise for mood disorders due to rapid, sustained results. Human neuroimaging studies have reported dramatic serotonin-2A receptor-(5-HT2AR)-dependent changes in functional brain reorganization that presumably reflect neuromodulation. However, the potent vasoactive effects of serotonin have been overlooked. We found psilocybin-mediated alterations to fMRI-HRFs in humans, suggesting potentially altered NVC. To assess the neuronal, hemodynamic, and neurovascular coupling (NVC) effects of the psychedelic 5-HT2AR agonist, 2,5-Dimethoxy-4-iodoamphetamine (DOI), wide-field optical imaging (WFOI) was used in awake Thy1-jRGECO1a mice during stimulus-evoked and resting-state conditions. While DOI partially altered tasked-based NVC, more pronounced NVC alterations occurred under resting-state conditions and were strongest in association regions. Further, calcium and hemodynamic activity reported different accounts of RSFC changes under DOI. Co-administration of DOI and the 5-HT2AR antagonist, MDL100907, reversed many of these effects. Dissociation between neuronal and hemodynamic signals emphasizes a need to consider neurovascular effects of psychedelics when interpreting blood-oxygenation-dependent neuroimaging measures.

Energy metabolism dysregulation, cerebrovascular aging, and time-restricted eating: Current evidence and proof-of-concept findings

Dysregulated energy metabolism is a hallmark of aging, including brain aging; thus, strategies to restore normal metabolic regulation are at the forefront of aging research. Intermittent fasting, particularly time-restricted eating (TRE), is one of these strategies. Despite its well-established effectiveness in improving metabolic outcomes in older adults, the effect of TRE on preserving or improving cerebrovascular health during aging remains underexplored. We explored how aging itself affects energy metabolism and contextualized these age-related changes to cerebrovascular health. We also conducted a literature search on PubMed and Scopus to identify and summarize current studies on TRE in older adults. Finally, we provided preliminary data from our proof-of-concept pilot trial on the effect of 6-month TRE on cerebrovascular health in older adults. Current evidence shows the potential of TRE to improve energy metabolism and physiological outcomes in older adults. TRE may improve cerebrovascular function indirectly due to its effect on glucose homeostasis. However, to date, direct evidence of the effect of TRE on cerebrovascular parameters is lacking. TRE is a well-tolerated and promising dietary intervention for promoting and maintaining cerebrovascular health in older adults. Further studies on TRE in older adults must be better controlled for energy balance to elucidate its independent effects from those of caloric restriction.

Data-based modeling of cerebral hemodynamics quantifies impairment of cerebral blood flow regulation in type-2 diabetes

We studied the regulation dynamics of cerebral blood velocity (CBv) at middle cerebral arteries (MCA) in response to spontaneous changes of arterial blood pressure (ABP), termed dynamic cerebral autoregulation (dCA), and end-tidal CO2 as proxy for blood CO2 tension, termed dynamic vasomotor reactivity (DVR), by analyzing time-series data collected at supine rest from 36 patients with Type-2 Diabetes Mellitus (T2DM) and 22 age/sex-matched non-diabetic controls without arterial hypertension. Our analysis employed a robust dynamic modeling methodology that utilizes Principal Dynamic Modes (PDM) to estimate subject-specific dynamic transformations of spontaneous changes in ABP and end-tidal CO2 (viewed as two "inputs") into changes of CBv at MCA measured via Transcranial Doppler ultrasound (viewed as the "output"). The quantitative results of PDM analysis indicate significant alterations in T2DM of both DVR and dCA in terms of two specific PDM contributions that rise to significance (p < 0.05). Our results further suggest that the observed DVR and dCA alterations may be due to reduction of cholinergic activity (based on previously published results from cholinergic blockade data) that may disturb the sympatho-vagal balance in T2DM. Combination of these two model-based "physio-markers" differentiated T2DM patients from controls (p = 0.0007), indicating diabetes-related alteration of cerebrovascular regulation, with possible diagnostic implications.

Cerebral blood flow regulation and cognitive performance in hypertension

We examined the relation between transcranial Doppler (TCD) markers of cerebral blood flow regulation and cognitive performance in hypertension (HT) patients to evaluate the predictive value of these markers for cognitive decline. We assessed dynamic cerebral autoregulation (dCA), vasoreactivity to carbon dioxide, and neurovascular coupling (NVC) in the middle (MCA) and posterior (PCA) cerebral arteries of 52 patients. Neuropsychological evaluation included the Montreal Cognitive Assessment and tests covering attention, executive function, processing speed, and memory. Notably, reduced rate time in the PCA significantly predicted better processing speed (p = 0.003). Furthermore, reduced overshoot systolic cerebral blood velocity in the PCA and reduced phase in the VLF range in the MCA (p = 0.021 and p = 0.017, respectively) significantly predicted better memory. Intriguingly, enhanced dCA in the MCA predicted poorer memory performance, while reduced NVC in the PCA predicted both superior processing speed and memory performance. These findings suggest that HT-induced changes in cerebral hemodynamics impact cognitive performance. Further research should verify these observations and elucidate whether these changes represent adaptive responses or neurovascular inefficiency. TCD markers might provide insights into HT-related cognitive decline.

Reduced neurovascular coupling of the visual network in migraine patients with aura as revealed with arterial spin labeling MRI: is there a demand-supply mismatch behind the scenes?

BACKGROUND

Although neuroimaging investigations have consistently demonstrated that "hyperresponsive" and "hyperconnected" visual cortices may represent the functional substrate of cortical spreading depolarization in patients with migraine with aura, the mechanisms which underpin the brain "tendency" to ignite the cortical spreading depolarization and, consequently, aura phenomenon are still matter of debate. Considering that triggers able to induce aura phenomenon constrain brain to increase global (such as physical activity, stressors and sleep abnormalities) or local (such as bright light visual stimulations) energy demand, a vascular supply unable to satisfy the increased energy requirement could be hypothesized in these patients.

METHODS

Twenty-three patients with migraine with aura, 25 patients with migraine without aura and 20 healthy controls underwent a 3-Tesla MRI study. Cerebral blood flow and local functional connectivity (regional homogeneity) maps were obtained and registered to the MNI space where 100 cortical regions were derived using a functional local-global normative parcellation. A surrogate estimate of the regional neurovascular coupling for each subject was obtained at each parcel from the correlation coefficient between the z-scored ReHo map and the z-scored cerebral blood flow maps.

RESULTS

A significantly higher regional cerebral blood flow across the visual cortex of both hemispheres (i.e. fusiform and lingual gyri) was detected in migraine with aura patients when compared to patients with migraine without aura (p < 0.05, corrected for multiple comparisons). Concomitantly, a significantly reduced neurovascular coupling (p < 0.05, false discovery rate corrected) in the primary visual cortex parcel (VIS-4) of the large-scale visual network was observed in the left hemisphere of patients with migraine with aura (0.23±0.03), compared to both patients with migraine without aura (0.32±0.05) and healthy controls (0.29±0.05).

CONCLUSIONS

Visual cortex neurovascular "decoupling" might represent the "link" between the exposure to trigger factors and aura phenomenon ignition. While physiological vascular oversupply may compensate neurovascular demand-supply at rest, it becomes inadequate in case of increased energy demand (e.g. when patients face with trigger factors) paving the way to the aura phenomenon ignition in patients with migraine with aura. Whether preventive treatments may exert their therapeutic activity on migraine with aura restoring the energy demands and cerebral blood flow trade-off within the visual network should be further investigated.

The complexity of cerebral blood flow regulation: the interaction of posture and vasomotor reactivity

Arterial carbon dioxide ([Formula: see text]) and posture influence the middle (MCAv) and posterior (PCAv) cerebral artery blood velocities, but there is paucity of data about their interaction and need for an integrated model of their effects, including dynamic cerebral autoregulation (dCA). In 22 participants (11 males, age 30.2 ± 14.3 yr), blood pressure (BP, Finometer), dominant MCAv and nondominant PCAv (transcranial Doppler ultrasound), end-tidal CO2 (EtCO2, capnography), and heart rate (HR, ECG) were recorded continuously. Two recordings (R) were taken when the participant was supine (R1, R2), two taken when the participant was sitting (R3, R4), and two taken when the participant was standing (R5, R6). R1, R3, and R5 consisted of 3 min of 5% CO2 through a mask and R2, R4, and R6 consisted of 3 min of paced hyperventilation. The effects of [Formula: see text] were expressed with a logistic curve model (LCM) for each parameter. dCA was expressed by the autoregulation index (ARI), derived by transfer function analysis. Standing shifted LCM to the left for MCAv (P < 0.001), PCAv (P < 0.001), BP (P = 0.03), and ARI (P = 0.001); downward for MCAv and PCAv (both P < 0.001), and upward for HR (P < 0.001). For BP, LCM was shifted downward by sitting and standing (P = 0.024). For ARI, the hypercapnic range of LCM was shifted upward during standing (P < 0.001). A more complete mapping of the combined effects of posture and arterial CO2 on the cerebral circulation and peripheral variables can be obtained with the LCM over a broad physiological range of EtCO2 values.NEW & NOTEWORTHY Data from supine, sitting, and standing postures were measured. Modeling the data with logistic curves to express the effects of CO2 reactivity on middle cerebral artery blood velocity (MCAv), posterior cerebral artery blood velocity (PCAv), heart rate, blood pressure (BP), and the autoregulation index (ARI), provided a more comprehensive approach to study the interaction of arterial CO2 with posture than in previous studies. Above all, shifts of the logistic curve model with changes in posture have shown interactions with [Formula: see text] that have not been previously demonstrated.

Altered functional connectivity in preterm neonates with intraventricular hemorrhage assessed using functional near-infrared spectroscopy

Intraventricular hemorrhage (IVH) is a common neurological injury following very preterm birth. Resting-state functional connectivity (RSFC) using functional magnetic resonance imaging (fMRI) is associated with injury severity; yet, fMRI is impractical for use in intensive care settings. Functional near-infrared spectroscopy (fNIRS) measures RSFC through cerebral hemodynamics and has greater bedside accessibility than fMRI. We evaluated RSFC in preterm neonates with IVH using fNIRS and fMRI at term-equivalent age, and compared fNIRS connectivity between healthy newborns and those with IVH. Sixteen very preterm born neonates were scanned with fMRI and fNIRS. Additionally, fifteen healthy newborns were scanned with fNIRS. In preterms with IVH, fNIRS and fMRI connectivity maps were compared using Euclidean and Jaccard distances. The severity of IVH in relation to fNIRS-RSFC strength was examined using generalized linear models. fNIRS and fMRI RSFC maps showed good correspondence. Connectivity strength was significantly lower in healthy newborns (p-value = 0.023) and preterm infants with mild IVH (p-value = 0.026) compared to infants with moderate/severe IVH. fNIRS has potential to be a new bedside tool for assessing brain injury and monitoring cerebral hemodynamics, as well as a promising biomarker for IVH severity in very preterm born infants.

Spatiotemporal relationships between neuronal, metabolic, and hemodynamic signals in the awake and anesthetized mouse brain

Neurovascular coupling (NVC) and neurometabolic coupling (NMC) provide the basis for functional magnetic resonance imaging and positron emission tomography to map brain neurophysiology. While increases in neuronal activity are often accompanied by increases in blood oxygen delivery and oxidative metabolism, these observations are not the rule. This decoupling is important when interpreting brain network organization (e.g., resting-state functional connectivity [RSFC]) because it is unclear whether changes in NMC/NVC affect RSFC measures. We leverage wide-field optical imaging in Thy1-jRGECO1a mice to map cortical calcium activity in pyramidal neurons, flavoprotein autofluorescence (representing oxidative metabolism), and hemodynamic activity during wake and ketamine/xylazine anesthesia. Spontaneous dynamics of all contrasts exhibit patterns consistent with RSFC. NMC/NVC relative to excitatory activity varies over the cortex. Ketamine/xylazine profoundly alters NVC but not NMC. Compared to awake RSFC, ketamine/xylazine affects metabolic-based connectomes moreso than hemodynamic-based measures of RSFC. Anesthesia-related differences in NMC/NVC timing do not appreciably alter RSFC structure.

Brain activation in older adults with hypertension and normotension during standing balance task: an fNIRS study

Background

Hypertension (HT) is a common chronic disease in older adults. It not only leads to dizziness and other symptoms affecting balance in older adults with HT but also affects the hemodynamics of the cerebral cortex. At present, potential neural mechanisms of balance control in older adults with HT are still unclear. Therefore, this study aimed to explore the differences in the center of pressure (COP) and cerebral cortex activation between older adults with HT and normotension (NT) during standing balance tasks. This study May provide guidance for the early detection of the risk of falls among older adults with HT and the development of clinical rehabilitation strategies.

Methods

In this cross-sectional study, 30 older adults with NT (NT group) and 27 older adults with HT (HT group) were subjected to three conditions: task 1, standing with eyes open on a stable surface; task 2, standing with eyes closed on a stable surface; and task 3, standing with eyes open on the surface of the foam pad. Cortical hemodynamic reactions were measured using functional near-infrared spectroscopy, and COP parameters were measured using a force plate.

Results

The mean velocity of the COP in the medial-lateral direction in the NT group was significantly higher than that in the HT group (F = 5.955, p = 0.018) during task 3. When proprioception was disturbed, the activation of the left premotor cortex and supplementary motor cortex in the HT group was significantly lower than that in the NT group (F = 14.381, p < 0.001).

Conclusion

The standing balance function of older adults with HT does not appear to be worse based on COP parameters than those of older adults with NT. This study revealed that the changes in the central cortex related to standing balance appear to be more indicative of balance control deficits in older adults with HT than changes in peripheral COP parameters, suggesting the importance of the early evaluation of cortical activation in older adults with HT at risk of falls.

Cognitive activity significantly affects the dynamic cerebral autoregulation, but not the dynamic vasoreactivity, in healthy adults

Introduction

Neurovascular coupling (NVC) is an important mechanism for the regulation of cerebral perfusion during intensive cognitive activity. Thus, it should be examined in terms of its effects on the regulation dynamics of cerebral perfusion and its possible alterations during cognitive impairment. The dynamic dependence of continuous changes in cerebral blood velocity (CBv), which can be measured noninvasively using transcranial Doppler upon fluctuations in arterial blood pressure (ABP) and CO2 tension, using end-tidal CO2 (EtCO2) as a proxy, can be quantified via data-based dynamic modeling to yield insights into two key regulatory mechanisms: the dynamic cerebral autoregulation (dCA) and dynamic vasomotor reactivity (DVR), respectively.

Methods

Using the Laguerre Expansion Technique (LET), this study extracted such models from data in supine resting vs cognitively active conditions (during attention, fluency, and memory tasks from the Addenbrooke's Cognitive Examination III, ACE-III) to elucidate possible changes in dCA and DVR due to cognitive stimulation of NVC. Healthy volunteers (n = 39) were recruited at the University of Leicester and continuous measurements of CBv, ABP, and EtCO2 were recorded.

Results

Modeling analysis of the dynamic ABP-to-CBv and CO2-to-CBv relationships showed significant changes in dCA, but not DVR, under cognitively active conditions compared to resting state.

Discussion

Interpretation of these changes through Principal Dynamic Mode (PDM) analysis is discussed in terms of possible associations between stronger NVC stimulation during cognitive tasks and enhanced sympathetic activation.

Disturbed Dynamic Brain Activity and Neurovascular Coupling in End-Stage Renal Disease Assessed With MRI

BACKGROUND

Pathophysiological mechanisms underlying cognitive impairment in end-stage renal disease (ESRD) remain unclear, with limited studies on the temporal variability of neural activity and its coupling with regional perfusion.

PURPOSE

To assess neural activity and neurovascular coupling (NVC) in ESRD patients, evaluate the classification performance of these abnormalities, and explore their relationships with cognitive function.

STUDY TYPE

Prospective.

POPULATION

Exactly 33 ESRD patients and 35 age, sex, and education matched healthy controls (HCs).

FIELD STRENGTH/SEQUENCE

The 3.0T/3D pseudo-continuous arterial spin labeling, resting-state functional MRI, and 3D-T1 weighted structural imaging.

ASSESSMENT

Dynamic (dfALFF) and static (sfALFF) fractional amplitude of low-frequency fluctuations and cerebral blood flow (CBF) were assessed. CBF-fALFF correlation coefficients and CBF/fALFF ratio were determined for ESRD patients and HCs. Their ability to distinguish ESRD patients from HCs was evaluated, alongside assessment of cerebral small vessel disease (CSVD) MRI features. All participants underwent blood biochemical and neuropsychological tests to evaluate cognitive decline.

STATISTICAL TESTS

Chi-squared test, two-sample t-test, Mann-Whitney U tests, covariance analysis, partial correlation analysis, family-wise error, false discovery rate, Bonferroni correction, area under the receiver operating characteristic curve (AUC) and multivariate pattern analysis. P < 0.05 denoted statistical significance.

RESULTS

ESRD patients exhibited higher dfALFF in triangular part of left inferior frontal gyrus (IFGtriang) and left middle temporal gyrus, lower CBF/dfALFF ratio in multiple brain regions, and decreased CBF/sfALFF ratio in bilateral superior temporal gyrus (STG). Compared with CBF/sfALFF ratio, dfALFF, and sfALFF, CBF/dfALFF ratio (AUC = 0.916) achieved the most powerful classification performance in distinguishing ESRD patients from HCs. In ESRD patients, decreased CBF/fALFF ratio correlated with more severe renal impairment, increased CSVD burden, and cognitive decline (0.4 < |r| < 0.6).

DATA CONCLUSION

ESRD patients exhibited abnormal dynamic brain activity and impaired NVC, with dynamic features demonstrating superior discriminative capacity and CBF/dfALFF ratio showing powerful classification performance.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 1.