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Key points We examined the interactive influence of hypoxia and exercise, and hypercapnia and exercise, on regional cerebral perfusion and sympathetic activation. Twenty healthy young adults (seven women) completed study trials including (1) rest in normoxia (SpO2${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$: ∼96%, PETCO2${{P}_{{\mathrm{ETC}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$: ∼36 mmHg), normocapnic hypoxia (SpO2${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$: ∼84%, PETCO2${{P}_{{\mathrm{ETC}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$: ∼36 mmHg), and normoxic hypercapnia (SpO2${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$: ∼98%, PETCO2${{P}_{{\mathrm{ETC}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$: ∼46 mmHg) and (2) unilateral rhythmic handgrip exercise (45% of maximal voluntary contraction at 1 Hz for 3 min) under the same gas conditions. Based on the exercising arm, blood flow in the contralateral internal carotid (ICABF) and ipsilateral vertebral (VABF) arteries, anterior and posterior cerebral O2 delivery (CDO2${\mathrm{C}}{{{\mathrm{D}}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$), and muscle sympathetic nerve activity (MSNA) were measured in each trial. During exercise in hypoxia, ICABF, VABF, anterior and posterior CDO2${\mathrm{C}}{{{\mathrm{D}}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$ were significantly lower, whereas total MSNA was significantly greater, than the sum of the responses evoked by either hypoxia or exercise alone. During exercise in hypercapnia, ICABF and anterior CDO2${\mathrm{C}}{{{\mathrm{D}}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$ were significantly greater, whereas MSNA was lower, than the sum of the responses evoked by either hypercapnia or exercise alone. The VABF and posterior CDO2${\mathrm{C}}{{{\mathrm{D}}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$ responses to hypercapnic exercise were not different from the summated responses. These findings suggest that the brain is hypoperfused and sympathetic outflow potentiated during hypoxic exercise, and that the brain is hyperperfused and sympathetic discharge constrained during hypercapnic exercise. The contrasting consequences for cerebral perfusion and sympathetic activation indicate a potential involvement of Cushing's mechanism in the autonomic control during exercise in healthy humans. Brain O2‐demand and ‐supply are mismatched, and muscle sympathetic nerve activity (MSNA) is enhanced in humans exercising at high altitude; the link between the two phenomena remains elusive. We evaluated the isolated and interactive effects of exercise, hypoxia, and hypercapnia on blood flow in the internal carotid (ICABF) and vertebral (VABF) arteries, and MSNA. The interaction of hypoxia and exercise was hypo‐additive for ICABF and VABF and anterior and posterior cerebral O2 delivery (CDO2${\mathrm{C}}{{{\mathrm{D}}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$), but hyper‐additive for MSNA. The interaction of hypercapnia and exercise was hyper‐additive for ICABF and anterior CDO2${\mathrm{C}}{{{\mathrm{D}}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$, additive for VABF and posterior CDO2${\mathrm{C}}{{{\mathrm{D}}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$, and hypo‐additive for MSNA. These observations indicate that a suboptimal brain perfusion during hypoxic exercise coincides with a potentiated sympathetic outflow, while a (supra‐)optimal brain perfusion during hypercapnic exercise coincides with a suppressed sympathetic outflow. Our findings suggest that Cushing's mechanism may play a role in the autonomic control in exercising humans. [ABSTRACT FROM AUTHOR]

Subarachnoid hemorrhage (SAH) is the deadliest form of hemorrhagic stroke; however, effective therapies are still lacking. Perfluorocarbons (PFCs) are lipid emulsion particles with great flexibility and their much smaller size as compared to red blood cells (RBCs) allows them to flow more efficiently within the blood circulation. Due to their ability to carry oxygen, a specific PFC-based emulsion, PFC-Oxygent, has been used as a blood substitute; however, its role in cerebral blood flow regulation is unknown. Adult C57BL/6 wildtype male mice were subjected to an endovascular perforation model of SAH followed by an intravenous (i.v.) injection of 9 ml/kg PFC-Oxygent or no treatment at 5 h after SAH. At 48 h after SAH, functional and anatomical outcomes were assessed. We found that SAH resulted in significant neurologic and motor deficits which were prevented by PFC-Oxygent treatment. We found that SAH-induced vasospasm, reduced RBC deformability, and augmented endothelial dysfunction were also restricted by PFC-Oxygent treatment. Moreover, mitochondrial activity and fusion proteins were also markedly decreased as assessed by oxidative phosphorylation (OXPHOS) after SAH. Interestingly, PFC-Oxygent treatment brought the mitochondrial activity close to the basal level. Moreover, SAH attenuated the level of phosphorylated AMP-activated protein kinase (pAMPK), whereas PFC treatment improved pAMPK levels. These data show the beneficial effects of PFC-Oxygent in limiting the severity of SAH. Further studies are needed to fully understand the mechanism through which PFC-Oxygent exerts its beneficial effects in limiting SAH severity. [ABSTRACT FROM AUTHOR]

An increasing body of evidence confirms the effectiveness of physical exercise (PE) in promoting brain health by preventing age-related cognitive decline and reducing the risk of neurodegenerative diseases. The benefits of PE are attributed to neuroplasticity processes which have been reported to enhance cerebral health. However, moderate to high-intensity PE is necessary to induce these responses and these intensities cannot always be achieved especially by people with physical limitations. As a countermeasure, electrical stimulation (ES) offers several benefits, particularly for improving physical functions, for various neurological diseases. This review aims to provide an overview of key mechanisms that could contribute to the enhancement in brain health in response to ES-induced exercise, including increases in cerebral blood flow, neuronal activity, and humoral pathways. This narrative review also focuses on the effects of ES protocols, applied to both humans and animals, on cognition. Despite a certain paucity of research when compared to the more classical aerobic exercise, it seems that ES could be of interest for improving cerebral health, particularly in people who have difficulty engaging in voluntary exercise. [ABSTRACT FROM AUTHOR]

Background: Sleep problem is a common complication of Alzheimer's disease (AD). Extensive preclinical studies have been performed to investigate the AD pathology. However, the pathophysiological consequence of AD complicated by sleep problem remains to be further determined. Purpose: To investigate brain metabolism and perfusion in an AD mouse model complicated by sleep problem, and subsequently identify potential imaging markers to better understand the associated pathophysiology. Methods: We examined the oxygen extraction fraction (OEF), cerebral metabolic rate of oxygen (CMRO2), and cerebral blood flow (CBF) using state-of-the-art MRI techniques in a cohort of 5xFAD model mice. Additionally, neuroinflammation, indicated by activated microglia, was assessed using histology techniques. Sleep fragmentation (SF) was utilized as a representative for sleep problems. Results: SF was associated with significant increases in OEF (P = 0.023) and CMRO2 (P = 0.029), indicating a state of hypermetabolism. CBF showed a significant genotype-by-sleep interaction effect (P = 0.026), particularly in the deep brain regions such as the hippocampus and thalamus. Neuroinflammation was primarily driven by genotype rather than SF, especially in regions with significant interaction effect in CBF measurements. Conclusion: These results suggest that brain metabolism and perfusion measurements are promising markers for studying the co-pathogenesis of AD and SF. [ABSTRACT FROM AUTHOR]

Background: Decreased cerebral oximetry (rSO2) in cardiac surgery is associated with postoperative delirium (POD). However, interventions optimizing intraoperative rSO2 are inconclusive. Methods: In this prospective observational cohort study, the relationship between rSO2, middle cerebral artery blood flow velocity (MCAV), and processed EEG was assessed in cardiac surgery patients with and without POD. MCAV was continuously recorded by transcranial Doppler sonography (TCD), together with continuous rSO2 and bispectral index (BIS) monitoring. Cardiopulmonary bypass (CPB) flow rate was adjusted according to body surface area. The cohort was divided into the POD and control groups, according to the postoperative results of the confusion assessment method (CAM/CAM-ICU), the 4A's test (4AT), and the Delirium Observation Scale (DOS). A mixed model analysis was performed for intraoperative raw data. The cerebral autoregulation index was calculated from TCD, rSO2, and arterial pressure values. Differences in impaired autoregulation were compared using the Mann–Whitney U test. Results: A total of 41 patients were included in this study. A total of 13 patients (36.11%) developed postoperative delirium. There were no significant differences in the baseline characteristics of patients with or without POD. Patients with POD had lower BIS values during CPB (adjusted mean difference −4.449 (95% CI [−7.978, −0.925])). RSO2 was not significantly reduced in POD, (adjusted mean difference: −5.320, 95% CI [−11.508, 0.874]). In contrast, MCAV was significantly increased in POD (10.655, 95% CI [0.491, 20.819]). The duration of cerebral autoregulation impairment did not differ significantly for TCD and cerebral oximetry-derived indices (p = 0.4528, p = 0.2715, respectively). Conclusions: Our results suggest that disturbed cerebral metabolism reflects a vulnerable brain which may be more susceptible to overperfusion during CPB, which can be seen in increased MCAV values. These phenomena occur irrespectively of cerebral autoregulation. [ABSTRACT FROM AUTHOR]

Intra-vital visualization of deep cerebrovascular structures and blood flow in the aging brain has been a difficult challenge in the field of neurovascular research, especially when considering the key role played by the cerebrovasculature in the pathogenesis of both vascular cognitive impairment and dementia (VCID) and Alzheimer's disease (AD). Traditional imaging methods face difficulties with the thicker skull of older brains, making high-resolution imaging and cerebral blood flow (CBF) assessment challenging. However, functional ultrasound (fUS) imaging, an emerging non-invasive technique, provides real-time CBF insights with notable spatial-temporal resolution. This study introduces an enhanced longitudinal fUS method for aging brains. Using elderly (24-month C57BL/6) mice, we detail replacing the skull with a polymethylpentene window for consistent fUS imaging over extended periods. Ultrasound localization mapping (ULM), involving the injection of a microbubble (<<10 μm) suspension allows for recording of high-resolution microvascular vessels and flows. ULM relies on the localization and tracking of single circulating microbubbles in the blood flow. A FIJI-based analysis interprets these high-quality ULM visuals. Testing on older mouse brains, our method successfully unveils intricate vascular specifics even in-depth, showcasing its utility for longitudinal studies that require ongoing evaluations of CBF and vascular aspects in aging-focused research. [ABSTRACT FROM AUTHOR]

The process by which cerebral blood flow (CBF) remains approximately constant in response to short-term variations in arterial blood pressure (ABP) is known as cerebral autoregulation. This classic view, that it remains constant over a wide range of ABP, has however been challenged by a growing number of studies. To provide an updated understanding of the static cerebral pressure-flow relationship and to characterise the autoregulation curve more rigorously, we conducted a comprehensive literature research. Results were based on 143 studies in healthy individuals aged 18 to 65 years. The mean sensitivities of CBF to changes in ABP were found to be 1.47 ± 0.71%/% for decreased ABP and 0.37 ± 0.38%/% for increased ABP. The significant difference in CBF directional sensitivity suggests that cerebral autoregulation appears to be more effective in buffering increases in ABP than decreases in ABP. Regression analysis of absolute CBF and ABP identified an autoregulatory plateau of approximately 20 mmHg (ABP between 80 and 100 mmHg), which is much smaller than the widely accepted classical view. Age and sex were found to have no effect on autoregulation strength. This data-driven approach provides a quantitative method of analysing static autoregulation that can be easily updated as more experimental data become available. [ABSTRACT FROM AUTHOR]

Pain catastrophizing is a prominent psychological factor that is strongly correlated with pain. Although the complex properties of pain catastrophizing vary across different pain phases, the contribution of chronic pain to its progression from a general trait to a higher state remains unclear. This study aimed to examine the neural mechanisms and degree to which pain catastrophizing is reinforced in the context of primary dysmenorrhea (PDM), one of the most prevalent gynaecological complaints experienced by women of reproductive age. Altogether, 29 women with moderate‐to‐severe PDM were included in this study. Arterial spin labelling was used to quantify the cerebral blood flow (CBF) in each participant in both the pain‐free and painful phases. The pain catastrophizing scale (PCS) was completed in two phases, and the Short‐Form McGill Pain Questionnaire was completed in the painful phase. Compared with pain catastrophizing in the pain‐free phase (PCSpf), pain catastrophizing in the painful phase (PCSp) is higher and positively correlated with the composite factor of menstrual pain. CBF analysis indicated that the PCSp is positively associated with CBF in the frontal cortex, hippocampus and amygdala. The reinforcement of pain catastrophizing correlates with CBF in the prefrontal cortex. Specifically, the medial prefrontal cortex, which correlates with pain state, plays a crucial role in mediating the reinforcing effect of pain in the PCSp. These results promote the mechanical comprehension of pain catastrophizing management in individuals with chronic pain. [ABSTRACT FROM AUTHOR]

We examined the extent to which apnoea‐induced extremes of oxygen demand/carbon dioxide production impact redox regulation of cerebral bioenergetic function. Ten ultra‐elite apnoeists (six men and four women) performed two maximal dry apnoeas preceded by normoxic normoventilation, resulting in severe end‐apnoea hypoxaemic hypercapnia, and hyperoxic hyperventilation designed to ablate hypoxaemia, resulting in hyperoxaemic hypercapnia. Transcerebral exchange of ascorbate radicals (by electron paramagnetic resonance spectroscopy) and nitric oxide metabolites (by tri‐iodide chemiluminescence) were calculated as the product of global cerebral blood flow (by duplex ultrasound) and radial arterial (a) to internal jugular venous (v) concentration gradients. Apnoea duration increased from 306 ± 62 s during hypoxaemic hypercapnia to 959 ± 201 s in hyperoxaemic hypercapnia (P ≤ 0.001). Apnoea generally increased global cerebral blood flow (all P ≤ 0.001) but was insufficient to prevent a reduction in the cerebral metabolic rates of oxygen and glucose (P = 0.015–0.044). This was associated with a general net cerebral output (v > a) of ascorbate radicals that was greater in hypoxaemic hypercapnia (P = 0.046 vs. hyperoxaemic hypercapnia) and coincided with a selective suppression in plasma nitrite uptake (a > v) and global cerebral blood flow (P = 0.034 to <0.001 vs. hyperoxaemic hypercapnia), implying reduced consumption and delivery of nitric oxide consistent with elevated cerebral oxidative–nitrosative stress. In contrast, we failed to observe equidirectional gradients consistent with S‐nitrosohaemoglobin consumption and plasma S‐nitrosothiol delivery during apnoea (all P ≥ 0.05). Collectively, these findings highlight a key catalytic role for hypoxaemic hypercapnia in cerebral oxidative–nitrosative stress. Key points: Local sampling of blood across the cerebral circulation in ultra‐elite apnoeists determined the extent to which severe end‐apnoea hypoxaemic hypercapnia (prior normoxic normoventilation) and hyperoxaemic hypercapnia (prior hyperoxic hyperventilation) impact free radical‐mediated nitric oxide bioavailability and global cerebral bioenergetic function.Apnoea generally increased the net cerebral output of free radicals and suppressed plasma nitrite consumption, thereby reducing delivery of nitric oxide consistent with elevated oxidative–nitrosative stress.The apnoea‐induced elevation in global cerebral blood flow was insufficient to prevent a reduction in the cerebral metabolic rates of oxygen and glucose.Cerebral oxidative–nitrosative stress was greater during hypoxaemic hypercapnia compared with hyperoxaemic hypercapnia and coincided with a lower apnoea‐induced elevation in global cerebral blood flow, highlighting a key catalytic role for hypoxaemia.This applied model of voluntary human asphyxia might have broader implications for the management and treatment of neurological diseases characterized by extremes of oxygen demand and carbon dioxide production. [ABSTRACT FROM AUTHOR]

The cerebral vasculature manages oxygen delivery by adjusting arterial blood in‐flow in the face of reductions in oxygen availability. Hypoxic cerebral vasodilatation, and the associated hypoxic cerebral blood flow reactivity, involve many vascular, erythrocytic and cerebral tissue mechanisms that mediate elevations in cerebral blood flow via micro‐ and macrovascular dilatation. This contemporary review focuses on in vivo human work – with reference to seminal preclinical work where necessary – on hypoxic cerebrovascular reactivity, particularly where recent advancements have been made. We provide updates with the following information: in humans, hypoxic cerebral vasodilatation is partially mediated via a – likely non‐obligatory – combination of: (1) nitric oxide synthases, (2) deoxygenation‐coupled S‐nitrosothiols, (3) potassium channel‐related vascular smooth muscle hyperpolarization, and (4) prostaglandin mechanisms with some contribution from an interrelationship with reactive oxygen species. And finally, we discuss the fact that, due to the engagement of deoxyhaemoglobin‐related mechanisms, reductions in O2 content via haemoglobin per se seem to account for ∼50% of that seen with hypoxic cerebral vasodilatation during hypoxaemia. We further highlight the issue that methodological impediments challenge the complete elucidation of hypoxic cerebral reactivity mechanisms in vivo in healthy humans. Future research is needed to confirm recent advancements and to reconcile human and animal findings. Further investigations are also required to extend these findings to address questions of sex‐, heredity‐, age‐, and disease‐related differences. The final step is to then ultimately translate understanding of these mechanisms into actionable, targetable pathways for the prevention and treatment of cerebral vascular dysfunction and cerebral hypoxic brain injury. [ABSTRACT FROM AUTHOR]

Objective: The morphology of basilar artery (BA) may affect posterior circulation blood perfusion. We aimed to investigate whether different degrees of BA tortuosity could lead to the alterations of posterior circulation perfusion. Methods: We collected 138 subjects with different BA tortuosity scores, including 32 cases of score 0, 45 cases of score 1, 43 cases of score 2, and 18 cases of score 3. A higher score represented a higher degree of BA tortuosity. Ordered logistic regression analysis was performed to investigate the risk factors for BA tortuosity. We quantitatively measured the cerebral blood flow (CBF) in eight posterior circulation brain regions using arterial spin labeling. SPSS 25.0 was used for statistical analysis. The correlation between the CBF and BA tortuosity was corrected by the Bonferroni method. The significance level was set at 0.006 (0.05/8). Results: Hypertension (HR: 2.39; 95%CI: 1.23–4.71; P = 0.01) and vertebral artery dominance (HR: 2.38; 95%CI: 1.10–4.67; P = 0.03) were risk factors for BA tortuosity. CBF in occipital gray matter (R = -0.383, P < 0.001), occipital white matter (R = -0.377, P < 0.001), temporal gray matter (R = -0.292, P = 0.001), temporal white matter (R = -0.297, P < 0.001), and cerebellum (R = -0.328, P < 0.001) were negatively correlated with BA tortuosity degree. No significant correlation was found between the BA tortuosity degree and CBF in hippocampus (R = -0.208, P = 0.014), thalamus (R = -0.001, P = 0.988) and brainstem (R = -0.204, P = 0.016). Conclusions: BA tortuosity could affect posterior circulation blood perfusion. CBF was negatively correlated with BA tortuosity degree. The morphology of BA may serve as a biomarker for posterior circulation and the severity of posterior circulation ischemia. [ABSTRACT FROM AUTHOR]

Alzheimer's disease is the most common form of dementia and is a challenge for the modern world due to the due to aging populations. Researchers are trying their best to understand the mechanisms of onset and find effective ways to treat and prevent this disease. The purpose of the following paper is to present the impact of physical activity in the development of Alzheimer's disease. Numerous studies confirm that regular workouts have a positive reflection in the form of slowing the aging of the brain and alleviation of neuropsychiatric symptoms in affected individuals. During muscle work irisin is produced, which plays an important role in the formation of neurons and exhibits an anti-inflammatory effects. This review also looks at the aspect of maintaining proper composition of the gut microbiota, whose imbalance can promote the process of neuronal inflammation and cognitive dysfunction. Attention is also given to issues of training intensity and the effect of of exercise on blood flow in the brain. All of these elements play an important role in preventing and slowing down neurodegeneration. Purpose : The purpose of this scientific paper is to review the current knowledge of the effects of physical activity on the development of Alzheimer's disease. Review methods : We conducted our study as a literature review based on information gathered from PubMed, Embase, Google Scholar using combinations of the following keywords : Alzheimer's disease ; dementia ; physical activity ; cerebral blood flow ; gut-brain axis ; irisin. The state of knowledge : Alzheimer's disease is the most common type of dementia and one of the main neurodegenerative disorders affecting elderly people. Numerous studies confirm that regular exercise has a positive effect on slowing down brain aging and alleviating neuropsychiatric symptoms in patients. According to current knowledge, nerve cell degeneration can be exacerbated by peripheral inflammation that occurs in obesity. An imbalance of bacterial flora in the gastrointestinal tract causes systemic inflammation in the body. This in turn leads to excessive production of pro-inflammatory cytokines and activation of microglia so that the blood-brain barrier becomes leaky. Maintaining the appropriate composition of the gut microbiota plays an important role, as its imbalance can promote neuronal inflammation and cognitive impairment. During physical activity, irisin protein is produced in muscle tissue, which plays an important role in neuronal formation and exhibits anti-inflammatory effects. Currently, there is evidence that irisin can provide a number of beneficial effects, mainly through mechanisms that positively affect the gut microbiome. Attention is also given to issues of training intensity and the effect of exercise on cerebral blood flow. All these factors play an important role in preventing and slowing down neurodegeneration. Conclusion : Based on a review of the available literature, a significant effect of physical activity on the development of Alzheimer's disease can be demonstrated. The accumulated data suggest that physical activity is one of the main protective factors against the development and progression of Alzheimer's disease. Physical activity is associated with a reduction in cardiovascular risk factors and an increase in neuroprotective changes. The neuroprotective effect of physical exercise is dependent on its intensity. In addition, the role of the gut microbiota has been shown to be important for maintaining normal cognitive function. The protein irisin may also have significant neuroprotective potential in relation to the development and progression of cognitive disorders. Physical activity may be one of the strategies to prevent an increase in the incidence of Alzheimer's disease with positive health, economic and social implications in the future. [ABSTRACT FROM AUTHOR]

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Intraventricular hemorrhage (IVH)4 is one of the most threatening neurological complications associated with preterm birth which can lead to long-term sequela such as cerebral palsy. Early recognition of IVH risk may prevent its occurrence and/or reduce its severity. Using multivariate logistic regression analysis, risk factors significantly associated with IVH were identified and integrated into risk scales. A special aspect of this study was the inclusion of mathematically calculated cerebral blood flow (CBF) as an independent predictive variable in the risk score. Statistical analysis was based on clinical data from 254 preterm infants with gestational age between 23 and 30  weeks of pregnancy. Several risk scores were developed for different clinical situations. Their efficacy was tested using ROC analysis, and validation of the best scores was performed on an independent cohort of 63 preterm infants with equivalent gestational age. The inclusion of routinely measured clinical parameters significantly improved IVH prediction compared to models that included only obstetric parameters and medical diagnoses. In addition, risk assessment with numerically calculated CBF demonstrated higher predictive power than risk assessments based on standard clinical parameters alone. The best performance in the validation cohort (with AUC  =  0.85 and TPR  =  0.94 for severe IVH, AUC  =  0.79 and TPR  =  0.75 for all IVH grades and FPR  =  0.48 for cases without IVH) was demonstrated by the risk score based on the MAP, pH, CRP, CBF and leukocytes count. [ABSTRACT FROM AUTHOR]

Introduction: Nociplastic pain (NP), a third category of chronic pain, offers a framework for elucidating its pathophysiology and treatment strategies. One of the characteristics of NP is comorbidity of symptoms other than pain, such as psychological and cognitive problems; therefore, these can be clues to understanding NP. Recently, we reported several cases with comorbid symptoms of attention-deficit/hyperactivity disorder (ADHD). Notably, ADHD medications, including methylphenidate (MP) and atomoxetine, improved chronic pain as well as the symptoms of ADHD. However, in clinical settings, identifying comorbid ADHD in patients with chronic pain is challenging, and underlying mechanisms have not been elucidated. To explore the common characteristics of brain function in patients with ADHD-comorbid NP, we identified brain regions where cerebral blood flow (CBF) distributions changed between pre- and post-treatment using single-photon emission computed tomography (SPECT). Additionally, we examined brain regions where CBF values correlated with clinical scores. Methods: We retrospectively studied 65 patients (mean age 53 ± 14 years; 30 males and 35 females) with ADHD-comorbid NP who underwent CBF-SPECT before and after ADHD medication initiation. Clinical scores included the clinical global impression severity (CGI-S), pain numerical rating scale, hospital anxiety and depression scale, pain catastrophizing scale, and Conners’ adult ADHD rating scale-self report scores. Voxel-based statistical methods were used to compare pre- and post-treatment CBF-SPECT images to identify significant differences and investigate brain regions correlated with clinical scores. Results: The CBF was higher in the precuneus, insular gyrus, and thalamus before treatment than after treatment (paired t-test, cluster-definition p < 0.001, cluster-extent threshold p < 0.05, with family-wise error [FWE] correction). The hyperperfusion in the precuneus was positively correlated with the CGI-S score and significantly reduced after treatment with MP (paired t-test, cluster-definition p < 0.005, cluster-extent threshold p < 0.05, with FWE correction). Conclusion: The finding of precuneal hyperperfusion may provide insight into the mechanisms of NP and help identify patients who would benefit most from ADHD medications. [ABSTRACT FROM AUTHOR]

Postural fluid shifts may directly affect respiratory control via a complex interaction of baro‐ and chemo‐reflexes, and cerebral blood flow. Few data exist concerning the steady state ventilatory responses during head‐down tilt. We examined the cardiorespiratory responses during acute 50° head‐down tilt (HDT) in 18 healthy subjects (mean [SD] age 27 [10] years). Protocol 1 (n = 8, two female) was 50° HDT from 60° head‐up posture sustained for 10 min, while exposed to normoxia, normoxic hypercapnia (5% CO2), hypoxia (12% inspired O2) or hyperoxic hypercapnia (95% O2, 5% CO2). Protocol 2 (n = 10, four female) was 50° HDT from supine, sustained for 10 min, while breathing either medical air or normoxic hypercapnic (5% CO2) gas. Ventilation (V̇E${{\dot{V}}_E}$, pneumotachograph), end‐tidal O2 and CO2 concentration and blood pressure (Finapres) were measured continuously throughout each protocol. Middle cerebral artery blood flow velocity (MCAv; transcranial Doppler) was also measured during protocol 2. Ventilation increased significantly (P < 0.05) compared to baseline during HDT in both hyperoxic hypercapnia (protocol 1 by mean [SD] 139 [26]%) and normoxic hypercapnia (protocol 1 by mean [SD] 131 [21]% and protocol 2 by 129 [23]%), despite no change in PETCO2${{P}_{{\mathrm{ETC}}{{{\mathrm{O}}}_2}}}$ or PETO2${{P}_{{\mathrm{ET}}{{{\mathrm{O}}}_2}}}$ from baseline. No change in V̇E${{\dot{V}}_E}$ was observed during HDT with medical air or hypoxia, and there was no significant change in MCAv during HDT compared to baseline. The absence of change in cerebral blood flow leads us to postulate that the augmented ventilatory response during steep HDT may involve mechanisms related to cerebral venous pressure and venous outflow. [ABSTRACT FROM AUTHOR]

Introduction: We aimed to verify the application value of the Alberta Stroke ProgramEarly CT Score (ASPECTS) based onmultiple post-labeling delay (multi-PLD) arterial spin labeling (ASL) for outcome assessment in acute ischemic stroke (AIS) patients. Method: The endpoint was modified Rankin scale score at 90 days (90-day mRS). Patients were divided into the good outcome (0-2) and poor outcome (3-6) groups. The independent samples t-test, Mann-Whitney U-test, and U-test were used to compare clinical and imaging parameters between groups. We used partial correlation analysis to evaluate the relationships between ASPECTS and outcomes. Multivariate logistic regression analysis was used to examine potential independent prognostic indicators. The receiver operating characteristic (ROC) curve analysis was used to evaluate the performance of the independent prognostic indicators in predicting outcomes. Results: Fifty-five AIS patients were included. The good outcome group had a lower baseline National Institutes of Health Stroke Scale (NIHSS; Z = -3.413, P < 0.001) and infarct core volume (ICV; Z = -3.114, P = 0.002) as well as higher cerebral blood flow (CBF)-ASPECTS (Z = -3.835, P < 0.001) and cerebral blood volume (CBV)-ASPECTS (Z = -4.099, P < 0.001). Higher CBF-ASPECTS (r = -0.459, P = 0.001), and CBV-ASPECTS (r = -0.502, P < 0.001) were associated with a lower 90-day mRS. The baseline NIHSS, CBF-ASPECTS, and CBV-ASPECTS were identified as independent prognostic indicators. The AUCs of the baseline NIHSS, CBF-ASPECTS, and CBV-ASPECTS were 83.3, 87.4, and 89.9%, respectively. Combining NIHSS with CBF-ASPECTS and CBV-ASPECTS, the AUC significantly improved to 96.3%. The combined three factors showed a significant difference compared to the baseline NIHSS (Z = 2.039, P = 0.041) and CBF-ASPECTS (Z = 2.099, P = 0.036), but no difference with CBV-ASPECTS (Z = 1.176, P = 0.239). Conclusions: The ASPECTS based on multi-PLD ASL is a valuable tool for identifying independent prognostic indicators and assessing clinical outcomes in AIS patients. The baseline NIHSS, combined with CBF-ASPECTS and CBV-ASPECTS, enhances the predictive efficacy of clinical outcomes in AIS patients. The CBV-ASPECTS alone can offer comparable predictive efficacy to the combination. [ABSTRACT FROM AUTHOR]

Normal pressure hydrocephalus (NPH) is associated with a reduction in cerebral blood flow and an ischemic metabolic state. Ischemia should exhaust the available autoregulation in an attempt to correct the metabolic imbalance. There is evidence of some retained autoregulation reserve in NPH. The aim of this study is to model the cerebral autoregulation in NPH to discover a solution to this apparent paradox. A lumped parameter model was developed utilizing the known limits of autoregulation in man. The model was tested by predicting the cerebral blood volume changes which would be brought about by changes in resistance. NPH and the post shunt state were then modeled using the known constraints provided from the literature. The model successfully predicted the cerebral blood volume changes brought about by altering the cerebral perfusion pressure to the limit of autoregulation. The model suggests that NPH is associated with a balanced increase in resistance within the arterial and venous outflow segments. The arterial resistance decreased after modelling shunt insertion. The model suggests that the cerebral blood flow is actively limited in NPH by arteriolar constriction. This may occur to minimize the rise in ICP by reducing the apparent CSF formation rate. [ABSTRACT FROM AUTHOR]

Introduction: Distinguishing meningiomas from other intracranial neoplasms is clinically relevant as the prognostic and therapeutic implications differ greatly and influence clinical decision making. Dynamic contrast-enhanced MRI (DCEMRI) is an imaging technique that assists with characterisation of physiologic alterations such as blood flow and tissue vascular permeability. Quantitative pharmacokinetic analysis utilising DCE-MRI has not been studied in canine neuro-oncology. Methods: A retrospective study was performed in canine patients that underwent DCE-MRI with an imaging diagnosis of an intracranial meningioma and surgery for histopathological diagnosis. Kinetic parameters Ktrans and cerebral blood flow were measured and compared to assess whether differences could be identified between meningiomas and other intracranial neoplasms. Results: Six dogs with meningiomas and 3 dogs with other intracranial neoplasms were included for statistical analysis. Cerebral blood flow values were found to be statistically higher within meningiomas compared to other intracranial neoplasms. Ktrans values were higher within meningiomas than in other types of intracranial tumours, however this difference did not reach statistical significance. Discussion: Based on the results of this study cerebral blood flow measurement can be utilised to differentiate canine intracranial meningiomas from other similar appearing intracranial tumours. [ABSTRACT FROM AUTHOR]

Background: Imaging examination of cerebral blood flow (CBF), oxygen extraction fraction (OEF), and metabolic rate of oxygen is crucial for understanding the normal functioning and pathophysiology of the brain. A recently developed method estimates the appearance time of cerebral blood (ATB) pixel-wise from the imaging examination of CBF alone. In this study, we aimed to test the potential of ATB as an indicator of OEF. Results: We retrospectively reviewed patients (n = 62) with suspected cerebrovascular disorders including steno-occlusive disease who underwent positron emission tomography (PET) with 15O-labelled tracers. Regarding the generated OEF and ATB images, a visual assessment was performed to test the consistency of the elevated OEF and delayed ATB. The OEF and ATB values and the absolute differences between their ipsilateral and contralateral sides were extracted and obtained for the entire hemisphere and the middle, anterior, and posterior cerebral arterial regions. Consistency was observed in 52 PET scans (83.9%) in visual assessment. The OEF and ATB values were moderately correlated (r = 0.553, p < 0.001), and the differences between their ipsilateral and contralateral sides were weakly correlated (r = 0.276, p < 0.001). Conclusion: Our results indicate the potential of ATB as an indicator of OEF. [ABSTRACT FROM AUTHOR]

AbstractThis study assessed the safety, feasibility, and acceptability of a novel device to monitor ischaemic stroke patients. The device captured electroencephalography (EEG) and electrocardiography (ECG) data to compute an ECG-based metric, termed the Electrocardiography Brain Perfusion index (EBPi), which may function as a proxy for cerebral blood flow (CBF). Seventeen ischaemic stroke patients wore the device for nine hours and reported feedback at 1, 3, 6 and 9 h regarding user experience, comfort, and satisfaction (acceptability). Safety was assessed as the number of adverse events reported. Feasibility was assessed as the percentage of uninterrupted EEG/ECG data recorded (data capture efficiency). No adverse events were reported, only minor incidences of discomfort. Overall device comfort (mean ± 1 standard deviation (SD) (range)) (92.5% ± 10.3% (57.0–100%)) and data capture efficiency (mean ± 1 SD (range)) (95.8% ± 6.8% (54.8–100%)) were very high with relatively low variance. The device didn’t restrict participants from receiving clinical care and rarely (n = 6) restricted participants from undertaking routine tasks. This study provides a promising evidence base for the deployment of the device in a clinical setting. If clinically validated, EBPi may be able to detect CBF changes to monitor early neurological deterioration and treatment outcomes, thus filling an important gap in current monitoring options.TRIAL REGISTRATION: The study was prospectively registered with the Australian New Zealand Clinical Trials Registry (ACTRN12622000112763). [ABSTRACT FROM AUTHOR]

There are differences within the literature regarding the upper frequency cut‐off point of the dynamic cerebral autoregulation (CA) high‐pass filter. The projection pursuit regression approach has demonstrated that the upper frequency limit is ∼0.07 Hz, whereas another approach [transfer function analysis (TFA) phase approaching zero] indicated a theoretical upper frequency limit for the high‐pass filter of 0.24 Hz. We investigated how these limits accurately represent the CA upper frequency limit, in addition to extending earlier findings with respect to biological sexes and across the cardiac cycle. Sixteen participants (nine females and seven males) performed repeated squat–stand manoeuvres at frequencies of 0.05, 0.10, 0.15, 0.20 and 0.25 Hz, with insonation of the middle and posterior cerebral arteries. Linear regression modelling with adjustment for sex and order of squat completion was used to compared TFA gain and phase with 0.25 Hz (above the theoretical limit of CA). The upper frequency limit of CA with TFA gain was within the range of 0.05–0.10 Hz, whereas TFA phase was within the range of 0.20–0.25 Hz, and consistent between vessels, between sexes and across the cardiac cycle. Females displayed greater middle cerebral artery gain compared with males (all P < 0.047), and no phase differences were present (all P > 0.072). Although sex‐specific differences were present for specific TFA metrics at a given frequency, the upper frequency limit of autoregulation was similar between cerebral conduit vessels, cardiac cycle phase and biological sex. Future work is warranted to determine whether an upper frequency limit exists with respect to hysteresis analyses. [ABSTRACT FROM AUTHOR]

Background: Sleep problem is a common complication of Alzheimer's disease (AD). Extensive preclinical studies have been performed to investigate the AD pathology. However, the pathophysiological consequence of AD complicated by sleep problem remains to be further determined. Purpose: To investigate brain metabolism and perfusion in an AD mouse model complicated by sleep problem, and subsequently identify potential imaging markers to better understand the associated pathophysiology. Methods: We examined the oxygen extraction fraction (OEF), cerebral metabolic rate of oxygen (CMRO2), and cerebral blood flow(CBF) using state-of-the-art MRI techniques in a cohort of 5xFAD model mice. Additionally, neuroinflammation, indicated by activated microglia, was assessed using histology techniques. Sleep fragmentation (SF) was utilized as a representative for sleep problems. Results: SF was associated with significant increases in OEF (P = 0.023) and CMRO2 (P = 0.029), indicating a state of hypermetabolism. CBF showed a significant genotype-by-sleep interaction effect (P = 0.026), particularly in the deep brain regions such as the hippocampus and thalamus. Neuroinflammation was primarily driven by genotype rather than SF, especially in regions with significant interaction effect in CBF measurements. Conclusion: These results suggest that brain metabolism and perfusion measurements are promising markers for studying the co-pathogenesis of AD and SF. [ABSTRACT FROM AUTHOR]

How do regional brain volume ratios and cerebral blood flow (CBF, mL/min) change with aging, and are there sex differences? This study aimed to comprehensively evaluate the relationships between regional brain volume ratios and CBF in healthy brains. The study participants were healthy volunteers who underwent three-dimensional T1-weighted MRI, time-of-flight MR angiography, and four-dimensional (4D) flow MRI between 2020 and 2022. The brain was automatically segmented into 21 brain subregions from 3D T1-weighted MRI, and CBF in 16 major intracranial arteries were measured by 4D flow MRI. The relationships between segmented brain volume ratios and CBFs around the circle of Willis were comprehensively investigated in each decade and sex. This study included 129 healthy volunteers (mean age ± SD, 48.2 ± 16.8; range, 22–92 years; 43 males and 86 females). The association was strongest between the cortical gray matter volume ratio and total outflow of the intracranial major arteries distal to the circle of Willis (Pearson’s correlation coefficient, r: 0.425). In addition, the mean flow of the total inflow and outflow around the circle of Willis were significantly greater in women than men, and significant left–right differences were observed in CBFs even on the peripheral side of the circle of Willis. Moreover, the correlation was strongest between the left cortical gray matter volume ratio and the combined flows of the left anterior and posterior cerebral arteries distal to the circle of Willis (r: 0.486). There was a trend toward greater total intracranial CBF, especially among women in their 40s and younger, who had a larger cortical gray matter volume. This finding may be one of the reasons for the approximately twofold higher incidence of cerebral aneurysms and subarachnoid hemorrhage, and a threefold higher incidence of migraine headaches. [ABSTRACT FROM AUTHOR]

Introduction: While increased baseline blood pressure (BP) is a prevalent comorbidity in the acute phase of ischemic stroke, the association between baseline BP and the state of hemispheric perfusion in patients with acute small subcortical infarcts (SSIs) has not been studied in detail. The aim of this study was to investigate the relationship between baseline BP and hemispheric cerebral blood flow (CBF) in acute SSIs. Methods: This retrospective study included 101 patients with acute SSIs. Baseline hemispheric CBF was assessed through co-registration of baseline CT perfusion imaging and follow-up diffusion-weighted imaging. The association between baseline BP, CBF, and different cerebral small vessel disease (CSVD) biomarkers was assessed. Results: Baseline systolic BP (SBP) and diastolic BP (DBP) were negatively associated with contralateral hemispheric CBF after multivariate-adjusted linear analysis (SBP: β = −0.001, 95% CI: −0.002 to 0.000, p = 0.030; DBP: β = −0.002, 95% CI: −0.003∼0.001, p = 0.006). Among other CSVD biomarkers, the presence of any cerebral microbleeds showed a significant association with lower CBF in the contralateral hemisphere of the infarct lesion (r = −0.270, p = 0.035). Conclusion: In patients with acute SSIs, increased baseline BP was associated with reduced CBF in the contralateral hemisphere of the infarct lesion, which probably could be interpreted by the exacerbation of the CSVD burden, suggesting a potential mechanistic link between BP autoregulation dysfunction and the aggravation of neurovascular impairment in SSIs. [ABSTRACT FROM AUTHOR]

Simple Summary: Traditionally, models of neurodegenerative diseases focus on changes within the central nervous system. However, growing evidence indicates there are prominent interactions between the cardiovascular system and neurodegenerative diseases. In this review, we discuss cardiovascular impairments in models of neurodegeneration, neurological impairments in models of cardiovascular disease, and what occurs when the two are combined as a first step toward improving our understanding of the pathophysiology of neurodegenerative diseases. Neurological diseases, including neurodegenerative diseases (NDDs), are the primary cause of disability worldwide and the second leading cause of death. The chronic nature of these conditions and the lack of disease-modifying therapies highlight the urgent need for developing effective therapies. To accomplish this, effective models of NDDs are required to increase our understanding of underlying pathophysiology and for evaluating treatment efficacy. Traditionally, models of NDDs have focused on the central nervous system (CNS). However, evidence points to a relationship between systemic factors and the development of NDDs. Cardiovascular disease and related risk factors have been shown to modify the cerebral vasculature and the risk of developing Alzheimer's disease. These findings, combined with reports of changes to vascular density and blood–brain barrier integrity in other NDDs, such as Huntington's disease and Parkinson's disease, suggest that cardiovascular health may be predictive of brain function. To evaluate this, we explore evidence for disruptions to the circulatory system in murine models of NDDs, evidence of disruptions to the CNS in cardiovascular disease models and summarize models combining cardiovascular disruption with models of NDDs. In this study, we aim to increase our understanding of cardiovascular disease and neurodegeneration interactions across multiple disease states and evaluate the utility of combining model systems. [ABSTRACT FROM AUTHOR]

The impact of physiological stressors on cerebral sympathetic nervous activity (SNA) remains controversial. We hypothesized that cerebral noradrenaline (NA) spillover, an index of cerebral SNA, would not change during both submaximal isometric handgrip (HG) exercise followed by a post-exercise circulatory occlusion (PECO), and supine dynamic cycling exercise. Twelve healthy participants (5 females) underwent simultaneous blood sampling from the right radial artery and right internal jugular vein. Right internal jugular vein blood flow was measured using Duplex ultrasound, and tritiated NA was infused through the participants' right superficial forearm vein. Heart rate was recorded via electrocardiogram and blood pressure was monitored using the right radial artery. Total NA spillover increased during HG (P = 0.049), PECO (P = 0.006), and moderate cycling exercise (P = 0.03) compared to rest. Cerebral NA spillover remained unchanged during isometric HG exercise (P = 0.36), PECO after the isometric HG exercise (P = 0.45), and during moderate cycling exercise (P = 0.94) compared to rest. These results indicate that transient increases in blood pressure during acute exercise involving both small and large muscle mass do not engage cerebral SNA in healthy humans. Our findings suggest that cerebral SNA may be non-obligatory for exercise-related cerebrovascular adjustments. [ABSTRACT FROM AUTHOR]

Objective: Intragastric administration of ninjin'yoeito (NYT), a traditional Japanese herbal medicine, reportedly prevents the decrease in baseline cerebral blood flow (CBF) in the cortex following gastric administration of water. We investigated the effect of NYT on baseline and dynamic changes in cerebral cortical arteriole diameter. Methods: Urethane‐anesthetized mice were intragastrically administered 1 g/kg NYT or distilled water (DW). The artery in the left parietal cortex was imaged using two‐photon microscopy. The baseline diameter of penetrating arterioles was measured before and 50–60 min after administration. Dynamic CBF and arteriole diameter changes before, during, and after transient occlusion of the left common carotid artery were measured approximately 10 min after administration. Results: DW decreased the baseline diameter of the penetrating arterioles, whereas NYT did not. During occlusion, the increase in penetrating arteriole diameter was comparable for DW and NYT; however, during reperfusion, the return to preocclusion diameter was slower for NYT than DW. Laser‐speckle contrast imaging confirmed that CBF, although comparable during occlusion, was higher during reperfusion for NYT than DW. Conclusions: These results suggest that NYT attenuates vasoconstriction in penetrating arterioles after intragastric administration and during cerebral reperfusion, contributing to CBF regulation. [ABSTRACT FROM AUTHOR]

Cerebral mitochondrial and hemodynamic abnormalities have been implicated in Bipolar Disorder pathophysiology, likely contributing to neurometabolic vulnerability–leading to worsen clinical outcomes and mood instability. To investigate neurometabolic vulnerability in patients with BD, we combined multi-modal quantitative MRI assessment of cerebral oxygenation with acute administration of Methylene Blue, a neurometabolic/hemodynamic modulator acting on cerebral mitochondria. Fifteen euthymic patients with chronic BD-type 1, and fifteen age/gender-matched healthy controls underwent two separate MRI sessions in a single-blinded randomized cross-over design, each after intravenous infusion of either MB (0.5 mg/kg) or placebo. MRI-based measures of Cerebral Blood Flow and Oxygen Extraction Fraction were integrated to compute Cerebral Metabolic Rate of Oxygen in Frontal Lobe, Anterior Cingulate, and Hippocampus–implicated in BD neurometabolic pathophysiology. Inter-daily variation in mood rating was used to assess mood instability. A decrease in global CBF and CMRO 2 was observed after acutely administrating MB to all participants. Greater regional CMRO 2 reductions were observed after MB, in patients compared to controls in FL (mean = −14.2 ± 19.5 % versus 2.3 ± 14.8 %), ACC (mean = −14.8 ± 23.7 % versus 2.4 ± 15.7 %). The effects on CMRO 2 in those regions were primarily driven by patients with longer disease duration and higher mood instability. Sample size; medications potentially impacting on response to MB. An altered neurometabolic response to MB, a mitochondrial/hemodynamic modulator, was observed in patients, supporting the hypothesis of vulnerability to neurometabolic stress in BD. Integrating quantitative imaging of cerebral oxygen metabolism with a mitochondrial-targeting pharmacological challenge could provide a novel biomarker of neurometabolic and cerebrovascular pathophysiology in BD. • Methylene Blue reduced cerebral blood flow and oxygen metabolism. • The response to Methylene Blue was altered in patients with Bipolar Disorder. • Disease duration and mood instability were associated with altered response. [ABSTRACT FROM AUTHOR]

INTRODUCTION: CD33 rs3865444 and hypertension (HTN) are related to cognitive impairment, individually. However, little is known about their combined effects on cognitive function in older adults. METHODS: This population‐based study included 4368 dementia‐free participants (age ≥65 years) in the Multimodal Interventions to Delay Dementia and Disability in Rural China (MIND‐China), with data available in 1044 persons for gray matter volume and 85 persons for cerebral blood flow (CBF). We used general linear regression and mediation models to examine the associations of rs3865444 and HTN with cognition, brain atrophy, and CBF. RESULTS: Among rs3865444 CC carriers, HTN and late‐life HTN were significantly associated with impaired cognition. Midlife and late‐life HTN were correlated with brain atrophy. CD33 rs3865444 CC moderated the mediation effect of gray matter volume on the association between HTN and global cognition. HTN was correlated with low CBF in rs3865444 CC carriers. DISCUSSION: There are synergistic associations of CD33 rs3865444 and HTN with brain and cognitive aging in dementia‐free older adults. [ABSTRACT FROM AUTHOR]

Arterial carbon dioxide ( Pa CO 2 ) 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 Pa CO 2 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 Pa CO 2 that have not been previously demonstrated. [ABSTRACT FROM AUTHOR]

Brain hypoperfusion is associated with cognitive impairment. Higher cerebrovascular impedance modulus (Z) may contribute to brain hypoperfusion. We tested hypotheses that patients with amnestic mild cognitive impairment (aMCI) (i.e., those who have a high risk of developing Alzheimer's disease) have higher Z than age-matched cognitively normal individuals, and that high Z is correlated with brain hypoperfusion. Fifty-eight patients with aMCI (67 ± 7 yr) and 25 cognitively normal subjects (CN, 65 ± 6 yr) underwent simultaneous measurements of carotid artery pressure (CAP, via applanation tonometry) and middle cerebral arterial blood velocity (CBV, via transcranial Doppler). Z was quantified using cross-spectral and transfer function analyses between dynamic changes in CBV and CAP. Patients with aMCI exhibited higher Z than NC (1.18 ± 0.34 vs. 1.01 ± 0.35 mmHg/cm/s, P = 0.044) in the frequency range from 0.78 to 4.29 Hz. The averaged Z in the frequency range (0.78–3.13 Hz) of high coherence (>0.9) was inversely correlated with total cerebral blood flow measured with 2-D Doppler ultrasonography normalized by the brain tissue mass (via structural MRI) across both patients with aMCI and NC (r = −0.311, P = 0.007), and in patients with aMCI alone (r = −0.306, P = 0.007). Our findings suggest that patients with aMCI have higher cerebrovascular impedance than cognitively normal older adults and that increased cerebrovascular impedance is associated with brain hypoperfusion. NEW & NOTEWORTHY: This is the first study to compare cerebrovascular impedance between patients with amnestic mild cognitive impairment (aMCI) and age-matched cognitively normal individuals. Patients with aMCI had higher cerebrovascular impedance modulus than age-matched cognitively normal individuals, which was correlated with brain hypoperfusion. These results suggest the presence of cerebrovascular dysfunction in the dynamic regulation of cerebral blood flow in older adults who have high risks of Alzheimer's disease. [ABSTRACT FROM AUTHOR]

In the brain, a microvascular sensory web coordinates oxygen delivery to regions of neuronal activity. This involves a dense network of capillaries that send conductive signals upstream to feeding arterioles to promote vasodilation and blood flow. Although this process is critical to the metabolic supply of healthy brain tissue, it may also be a point of vulnerability in disease. Deterioration of capillary networks is a feature of many neurological disorders and injuries and how this web is engaged during vascular damage remains unknown. We performed in vivo two-photon microscopy on young adult mural cell reporter mice and induced focal capillary injuries using precise two-photon laser irradiation of single capillaries. We found that ~59% of the injuries resulted in regression of the capillary segment 7 to 14 d following injury, and the remaining repaired to reestablish blood flow within 7 d. Injuries that resulted in capillary regression induced sustained vasoconstriction in the upstream arteriole-capillary transition (ACT) zone at least 21 days postinjury in both awake and anesthetized mice. The degree of vasomotor dynamics was chronically attenuated in the ACT zone consequently reducing blood flow in the ACT zone and in secondary, uninjured downstream capillaries. These findings demonstrate how focal capillary injury and regression can impair the microvascular sensory web and contribute to cerebral hypoperfusion. [ABSTRACT FROM AUTHOR]

Background: Ictal brain perfusion SPECT provides higher sensitivity for the identification of the epileptic seizure onset zone (SOZ) than interictal SPECT. However, ictal SPECT is demanding due to the unpredictable waiting period for the next seizure to allow for ictal tracer injection. Thus, starting with an interictal scan and skipping the ictal scan if the interictal scan provides a SOZ candidate with high confidence could be an efficient approach. The current study estimated the rate of high-confidence SOZ candidates and the false lateralization rate among them for interictal and ictal SPECT. Methods: 177 patients (48% females, median age 38y, interquartile range 27–48y) with ictal and interictal SPECT acquired with 99mTc-HMPAO (n = 141) or -ECD (n = 36) were included retrospectively. The vast majority of the patients was suspected to have temporal lobe epilepsy. Visual interpretation of the SPECT data was performed independently by 3 readers in 3 settings: "interictal only" (interictal SPECT and statistical hypoperfusion map), "ictal only" (ictal SPECT and hyperperfusion map), and "full" setting (side-by-side interpretation of ictal and interictal SPECT including statistical maps and SISCOM analysis). The readers lateralized the SOZ (right, left, none) and characterized their confidence using a 5-score. A case was considered "lateralizing with high confidence" if all readers lateralized to the same hemisphere with at least 4 of 5 confidence points. Lateralization of the SOZ in the "full" setting was used as reference standard. Results: The proportion of "lateralizing with high confidence" cases was 4.5/31.6/38.4% in the "interictal only"/"ictal only"/"full" setting. One (12.5%) of the 8 cases that were "lateralizing with high confidence" in the "interictal only" setting lateralized to the wrong hemisphere. Among the 56 cases that were "lateralizing with high confidence" in the "ictal only" setting, 54 (96.4%) were also lateralizing in the "full" setting, all to the same hemisphere. Conclusions: Starting brain perfusion SPECT in the presurgical evaluation of epilepsy with an interictal scan to skip the ictal scan in case of a high-confidence interictal SOZ candidate is not a useful approach. In contrast, starting with an ictal scan to skip the interictal scan in case of a high-confidence ictal SOZ candidate can be recommended. [ABSTRACT FROM AUTHOR]

Introduction: Patients with coronary artery disease (CAD) have a higher risk of developing cognitive impairment and mental health disorders compared to the general population. Physical exercise might improve their brain health. The overall goal of the HEART-BRAIN randomized controlled trial (RCT) is to investigate the effects of different types of exercise on brain health outcomes in patients with CAD, and the underlying mechanisms. Methods: This three-arm, single-blinded RCT will include 90 patients with CAD (50-75 years). Participants will be randomized into: (1) control group--usual care (n = 30), (2) aerobic high-intensity interval training (HIIT) (n = 30), or (3) HIIT combined with resistance exercise training (n = 30). The 12-week intervention includes 3 supervised sessions (45-min each) per week for the exercise groups. Outcomes will be assessed at baseline and post-intervention. The primary outcome is to determine changes in cerebral blood flow assessed by magnetic resonance imaging. Secondary outcomes include changes in brain vascularization, cognitive measures (i.e., general cognition, executive function and episodic memory), and cardiorespiratory fitness. Additional health-related outcomes, and several potential mediators and moderators will be investigated (i.e., brain structure and function, cardiovascular and brain-based biomarkers, hemodynamics, physical function, body composition, mental health, and lifestyle behavior). Conclusion: The HEART-BRAIN RCT will provide novel insights on how exercise can impact brain health in patients with CAD and the potential mechanisms explaining the heart-brain connection, such as changes in cerebral blood flow. The results may have important clinical implications by increasing the evidence on the effectiveness of exercise-based strategies to delay cognitive decline in this high-risk population. [ABSTRACT FROM AUTHOR]

Background: Sepsis-associated encephalopathy (SAE) patients often experience changes in intracranial pressure and impaired cerebral autoregulation. Mean arterial pressure (MAP) plays a crucial role in cerebral perfusion pressure, but its relationship with mortality in SAE patients remains unclear. This study aims to investigate the relationship between MAP and the risk of 28-day and in-hospital mortality in SAE patients, providing clinicians with the optimal MAP target. Methods: We retrospectively collected clinical data of patients diagnosed with SAE on the first day of ICU admission from the MIMIC-IV (v2.2) database. Patients were divided into four groups based on MAP quartiles. Kruskal-Wallis H test and Chi-square test were used to compare clinical characteristics among the groups. Restricted cubic spline and segmented Cox regression models, both unadjusted and adjusted for multiple variables, were employed to elucidate the relationship between MAP and the risk of 28-day and in-hospital mortality in SAE patients and to identify the optimal MAP. Subgroup analyses were conducted to assess the stability of the results. Results: A total of 3,816 SAE patients were included. The Q1 group had higher rates of acute kidney injury and vasoactive drug use on the first day of ICU admission compared to other groups (P < 0.01). The Q1 and Q4 groups had longer ICU and hospital stays (P < 0.01). The 28-day and in-hospital mortality rates were highest in the Q1 group and lowest in the Q3 group. Multivariable adjustment restricted cubic spline curves indicated a nonlinear relationship between MAP and mortality risk (P for nonlinearity < 0.05). The MAP ranges associated with HRs below 1 for 28-day and in-hospital mortality were 74.6–90.2 mmHg and 74.6–89.3 mmHg, respectively.The inflection point for mortality risk, determined by the minimum hazard ratio (HR), was identified at a MAP of 81.5 mmHg. The multivariable adjusted segmented Cox regression models showed that for MAP < 81.5 mmHg, an increase in MAP was associated with a decreased risk of 28-day and in-hospital mortality (P < 0.05). In Model 4, each 5 mmHg increase in MAP was associated with a 15% decrease in 28-day mortality risk (HR: 0.85, 95% CI: 0.79–0.91, p < 0.05) and a 14% decrease in in-hospital mortality risk (HR: 0.86, 95% CI: 0.80–0.93, p < 0.05). However, for MAP ≥ 81.5 mmHg, there was no significant association between MAP and mortality risk (P > 0.05). Subgroup analyses based on age, congestive heart failure, use of vasoactive drugs, and acute kidney injury showed consistent results across different subgroups.Subsequent analysis of SAE patients with septic shock also showed results similar to those of the original cohort.However, for comatose SAE patients (GCS ≤ 8), there was a negative correlation between MAP and the risk of 28-day and in-hospital mortality when MAP was < 81.5 mmHg, but a positive correlation when MAP was ≥ 81.5 mmHg in adjusted models 2 and 4. Conclusion: There is a nonlinear relationship between MAP and the risk of 28-day and in-hospital mortality in SAE patients. The optimal MAP target for SAE patients in clinical practice appears to be 81.5 mmHg. [ABSTRACT FROM AUTHOR]

Introduction: Frontotemporal lobar degeneration (FTLD) is associated with FTLD due to tau (FTLD-tau) or TDP (FTLD-TDP) inclusions found at autopsy. Arterial Spin Labeling (ASL) MRI is often acquired in the same session as a structural T1- weighted image (T1w), enabling detection of regional changes in cerebral blood flow (CBF). We hypothesize that ASL-T1w registration with more degrees of freedom using boundary-based registration (BBR) will better align ASL and T1w images and show increased sensitivity to regional hypoperfusion differences compared to manual registration in patient participants. We hypothesize that hypoperfusion will be associated with a clinical measure of disease severity, the FTLD-modified clinical dementia rating scale sum-of-boxes (FTLD-CDR). Materials and methods: Patients with sporadic likely FTLD-tau (sFTLD-tau; N = 21), with sporadic likely FTLD-TDP (sFTLD-TDP; N = 14), and controls (N = 50) were recruited from the Connectomic Imaging in Familial and Sporadic Frontotemporal Degeneration project (FTDHCP). Pearson's Correlation Coefficients (CC) were calculated on cortical vertex-wise CBF between each participant for each of 3 registration methods: (1) manual registration, (2) BBR initialized with manual registration (manual+BBR), (3) and BBR initialized using FLIRT (FLIRT+BBR). Mean CBF was calculated in the same regions of interest (ROIs) for each registration method after image alignment. Paired t-tests of CC values for each registration method were performed to compare alignment. Mean CBF in each ROI was compared between groups using t-tests. Differences were considered significant at p < 0.05 (Bonferroni-corrected). We performed linear regression to relate FTLD-CDR to mean CBF in patients with sFTLD-tau and sFTLD-TDP, separately (p < 0.05, uncorrected). Results: All registration methods demonstrated significant hypoperfusion in frontal and temporal regions in each patient group relative to controls. All registration methods detected hypoperfusion in the left insular cortex, middle temporal gyrus, and temporal pole in sFTLD-TDP relative to sFTLD-tau. FTLD- CDR had an inverse association with CBF in right temporal and orbitofrontal ROIs in sFTLD-TDP. Manual+BBR performed similarly to FLIRT+BBR. Discussion: ASL is sensitive to distinct regions of hypoperfusion in patient participants relative to controls, and in patients with sFTLD-TDP relative to sFTLD-tau, and decreasing perfusion is associated with increasing disease severity, at least in sFTLD-TDP. BBR can register ASL-T1w images adequately for controls and patients. [ABSTRACT FROM AUTHOR]

Background: The periaqueductal gray (PAG) is at the center of a powerful descending antinociceptive neuronal network, and is a key node in the descending pain regulatory system of pain. However, less is known about the altered perfusion of PAG in chronic migraine (CM). Aim: To measure the perfusion of PAG matter, an important structure in pain modulation, in CM with magnetic resonance (MR) perfusion without contrast administration. Methods: Three‐dimensional pseudocontinuous arterial spin labeling (3D‐PCASL) and brain structure imaging were performed in 13 patients with CM and 15 normal subjects. The inverse deformation field generated by brain structure image segmentation was applied to the midbrain PAG template to generate individualized PAG. Then the perfusion value of the PAG area of the midbrain was extracted based on the individual PAG mask. Results: Cerebral blood flow (CBF) value of PAG in CM patients (47.98 ± 8.38 mL/100 mg min) was significantly lower than that of the control group (59.87 ± 14.24 mL/100 mg min). Receiver operating characteristic (ROC) curve analysis showed that the area under the curve was 0.77 (95% confidence interval [CI], 0.60, 0.94), and the cutoff value for the diagnosis of CM was 54.83 mL/100 mg min with a sensitivity 84.60% and a specificity 60%. Conclusion: Imaging evidence of the impaired pain conduction pathway in CM may be related with the decreased perfusion in the PAG, which could be considered as an imaging biomarker for the diagnosis and therapy evaluation. [ABSTRACT FROM AUTHOR]

Background: Intracranial atherosclerotic stenosis (ICAS) is one of the most important independent risk factors for stroke that is closely related to the occurrence of cognitive impairment. The relationship between ICAS and vascular cognitive impairment (VCI) remains unclear. Cerebral hemodynamic changes are one of the main causes of cognitive impairment. Computed tomographic perfusion (CTP) imaging can quantitatively analyze cerebral blood perfusion and quantify cerebral hemodynamic changes. Previous research on the relationship between hypoperfusion induced by ICAS and cognitive impairment, as well as its underlying mechanisms, remains relatively insufficient. This study is dedicated to elucidating the characteristics and potential mechanisms of cognitive impairment in ICAS patients with abnormal perfusion, utilizing CTP imaging as our primary investigative tool. Methods: This study recruited 82 patients who suffer from non‐disabling ischemic stroke (IS group) and 28 healthy controls. All participants underwent comprehensive neuropsychological assessments both collectively and individually, in addition to CTP imaging. Within the patient group, we further categorized individuals into two subgroups: the ischemic penumbra group (IP, N = 28) and the benign oligemia group (BO, N = 54), based on CTP parameters—Tmax. The correlations between cognitive function and abnormal perfusion were explored. Results: The cognitive function, including the overall cognitive, memory, attention, executive functions, and language, was significantly impaired in the IS group compared with that in the control group. Further, there are statistical differences in the stroop color–word test‐dot (Stroop‐D) and Montreal Cognitive Assessment (MoCA) sub‐items (memory + language) between the BO and IP groups. In the BO group, the score of Stroop‐D is lower, and the MoCA sub‐items are higher than the IP group. There is no correlation between CTP parameters and cognitive function. Conclusion: Cognitive function is significantly impaired in patients with ICAS, which is related to cerebral perfusion. Executive, memory, and language function were better preserved in ICAS patients without IP. Hence, this study posits that managing hypoperfusion induced by ICAS may play a pivotal role in the development of VCI. [ABSTRACT FROM AUTHOR]

Cerebral Autoregulation (CA) is an important physiological mechanism stabilizing cerebral blood flow (CBF) in response to changes in cerebral perfusion pressure (CPP). By maintaining an adequate, relatively constant supply of blood flow, CA plays a critical role in brain function. Quantifying CA under different physiological and pathological states is crucial for understanding its implications. This knowledge may serve as a foundation for informed clinical decision-making, particularly in cases where CA may become impaired. The quantification of CA functionality typically involves constructing models that capture the relationship between CPP (or arterial blood pressure) and experimental measures of CBF. Besides describing normal CA function, these models provide a means to detect possible deviations from the latter. In this context, a recent white paper from the Cerebrovascular Research Network focused on Transfer Function Analysis (TFA), which obtains frequency domain estimates of dynamic CA. In the present paper, we consider the use of time-domain techniques as an alternative approach. Due to their increased flexibility, time-domain methods enable the mitigation of measurement/physiological noise and the incorporation of nonlinearities and time variations in CA dynamics. Here, we provide practical recommendations and guidelines to support researchers and clinicians in effectively utilizing these techniques to study CA. [ABSTRACT FROM AUTHOR]

Neurovascular coupling (NVC) is the functional hyperemia of the brain responding to local neuronal activity. It is mediated by astrocytes and affected by subcortical ascending pathways in the cortex that convey information, such as sensory stimuli and the animal condition. Here, we investigate the influence of the raphe serotonergic system, a subcortical ascending arousal system in animals, on the modulation of cortical NVC and cerebral blood flow (CBF). Raphe serotonergic neurons were optogenically activated for 30 s, which immediately awakened the mice from non-rapid eye movement sleep. This caused a biphasic cortical hemodynamic change: a transient increase for a few seconds immediately after photostimulation onset, followed by a large progressive decrease during the stimulation period. Serotonergic neuron activation increased intracellular Ca2+ levels in cortical pyramidal neurons and astrocytes, demonstrating its effect on the NVC components. Pharmacological inhibition of cortical neuronal firing activity and astrocyte metabolic activity had small hypovolemic effects on serotonin-induced biphasic CBF changes, while blocking 5-HT1B receptors expressed primarily in cerebral vasculature attenuated the decreasing CBF phase. This suggests that serotonergic neuron activation leading to animal awakening could allow the NVC to exert a hyperemic function during a biphasic CBF response, with a predominant decrease in the cortex. [ABSTRACT FROM AUTHOR]

Aims: Extended fasting–postprandial switch intermitting time has been shown to affect Alzheimer's disease (AD). Few studies have investigated the cerebral perfusion response to fasting–postprandial metabolic switching (FMS) in AD patients. We aimed to evaluate the cerebral perfusion response to FMS in AD patients. Methods: In total, 30 AD patients, 32 mild cognitive impairment (MCI) patients, and 30 healthy control individuals (HCs) were included in the quantification of cerebral perfusion via cerebral blood flow (CBF). The cerebral perfusion response to FMS was defined as the difference (ΔCBF) between fasting and postprandial CBF. Results: Patients with AD had a regional negative ΔCBF in the anterior temporal lobe, part of the occipital lobe and the parietal lobe under FMS stimulation, whereas HCs had no significant ΔCBF. The AD patients had lower ΔCBF values in the right anterior temporal lobe than the MCI patients and HCs. ΔCBF in the anterior temporal lobe was negatively correlated with cognitive severity and cognitive reserve factors in AD patients. Conclusions: AD patients exhibited a poor ability to maintain cerebral perfusion homeostasis under FMS stimulation. The anterior temporal lobe is a distinct area that responds to FMS in AD patients and negatively correlates with cognitive function. [ABSTRACT FROM AUTHOR]

Visual stimuli from green plants have positive effects on mental health. This study aimed to compare human responses to varying plant types [live, artificial, two-dimensional (2D), and three-dimensional (3D) plant models] as visual stimuli. Thirty adults (age, 29.9 ± 11.5 years) viewed each plant form while an electroencephalography (EEG) measured their brain activity. Psychological responses were assessed using the semantic differential method (SDM). No significant differences were observed among visual stimuli; however, brain activity differences varied between male and female participants. Males who observed live and artificial plants had a higher relative alpha (RA) spectrum (RAS) and relative fast alpha (RFA) spectrum frequencies at Fp1 and Fp2 (P < 0.05 and P < 0.01 vs. P < 0.05 and P < 0.01, respectively), indicating greater emotional stability. Similarly, male participants who viewed 2D models had higher RA and RFA frequencies at Fp1 (P < 0.01, P < 0.01) and Fp2 (P < 0.05, P < 0.01). Male participants who observed 3D models exhibited higher RA, RSA, and RFA frequencies at Fp1 (P < 0.01). Live and artificial plants were deemed the most calming (P < 0.01). Both sexes found live plants to be the most pleasant (males: P < 0.01; females: P < 0.05) and natural (males: P < 0.001; females: P < 0.01). Overall, alpha wave differences were not significant among plant types, and live plants elicited a trend toward emotional stability. These findings suggest that 3D plant models can be as effective as real plants in psychophysiological applications, indicating their potential benefits for enhancing mental health in urban environments. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the psychophysiological effects of horticultural activities on the prefrontal cortex (PFC) to understand how horticultural activities can influence mental health and cognitive function. This study involved 39 adults with an average age of 54.6 years (±12.5 years) and was conducted in a laboratory setting at Konkuk University. The impact of five different types of horticultural activities--sowing, transplanting, planting, harvesting, and packaging--on PFC oxyhemoglobin (oxy-HB) concentrations was assessed. Functional near-infrared spectroscopy (fNIRS) was used to measure oxy-HB levels in the PFC while participants engaged in each activity for 90 seconds. The results indicated that the overall PFC oxy-HB concentration was at its lowest during planting and at its highest during sowing (P < 0.001). In the right PFC, oxy-HB was also at its lowest during planting and at its highest during sowing (P < 0.01). In the left PFC, the lowest oxy-HB concentrations were observed during both planting and harvesting, whereas the highest oxy-HB concentrations were observed during transplanting and sowing (P < 0.001). Additionally, sex-based differences were noted, with females showing significantly lower oxy-HB concentrations during sowing (P < 0.05) and transplanting (P < 0.01) than those of males. These findings suggested that psychophysiological responses, as indicated by oxy-HB concentrations, vary depending on the type of horticultural activity and by sex. [ABSTRACT FROM AUTHOR]

Purpose: Short-term intake of the egg-protein hydrolysate Newtricious (NWT)-03 improved executive function, but underlying mechanisms and long-term effects, including other cognitive domains, are unknown. Methods: A 36-week randomized controlled trial involving 44 overweight/obese individuals experiencing elevated Subjective Cognitive Failures (SCF; aged 60–75 years) assessed the impact of daily consumption of 5.7 g of NWT-03 or placebo powders on cognitive performance (psychomotor speed, executive function, memory) and Cerebral Blood Flow (CBF), a marker of brain vascular function. Cognitive performance was evaluated using a neurophysiological test battery (CANTAB) and CBF was measured using magnetic resonance imaging perfusion method Arterial Spin Labeling (ASL). Serum samples were collected to determine brain-derived neurotrophic factor (BDNF) concentrations. Results: Anthropometrics, and energy and nutrient intakes remained stable throughout the trial. NWT-03 was well tolerated, and compliance was excellent (median: 99%; range: 87–103%). No overall intervention effects were observed on cognitive performance or CBF, but post-hoc analyses revealed significant improvements on executive function in women, but not men. Specifically, a reduction of 74 ms in reaction latency on the multitasking task (95% CI: −134 to −15; p = 0.02), a reduction of 9 between errors (95%CI: −14 to −3; p < 0.001), and a reduction of 9 total errors (95%CI: −15 to −3; p < 0.001) on the spatial working memory task were found in women. No intervention effects were observed on serum BDNF concentrations (p = 0.31). Conclusion: Long-term consumption of NWT-03 improved multitasking abilities and working memory in women with elevated SCF. Brain vascular function remained unaffected. Sex differences in executive function require additional clarification. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the effect of posture changes on vascular compliance in intracranial (brain) versus extracranial vascular beds (forearm). Eighteen young adults (nine females) performed a supine-to-seated-to-standing protocol involving 5 min of rest in each position. Continuous blood pressure, middle cerebral artery (MCA) blood velocity, and brachial artery blood velocity were recorded at each posture. Three to five consecutive steady-state cardiac cycles at each posture were analyzed by a four-element lumped parameter modified Windkessel model to calculate vascular compliance. Mean arterial pressure (MAP) increased from supine to seated (76(9) vs. 81(12) mmHg; P = 0.006) and from supine to standing (76(9) vs. 82(13) mmHg; P = 0.034). Mean blood flow was greater in the MCA relative to the forearm (forearm: 40(5) mL·min−1, MCA: 224(17) mL·min−1; main effect P < 0.001). Conversely, vascular resistance (forearm: 3.25(0.50) mmHg−1·mL·min−1, brain: 0.36(0.04) mmHg−1·mL·min−1; main effect P < 0.001) and compliance (forearm: 0.010(0.001) mL·min−1·mmHg−1, brain: 0.005(0.001) mL·min−1·mmHg−1; main effect P = 0.001) were greater in the forearm compared to the brain. Significant main effects of posture were observed with decreasing values in upright positions for mean blood flow (P = 0.001) in both vascular beds, but not for resistance (P = 0.163) or compliance (P = 0.385). There were no significant interaction effects between vascular bed and posture for mean flow (P = 0.057), resistance (P = 0.258), or compliance (P = 0.329). This study provides evidence that under steady-state conditions, posture does not affect cerebrovascular compliance. [ABSTRACT FROM AUTHOR]

Summary: Background: Noradrenaline is a standard treatment for hypotension in acute care. The precise effects of noradrenaline on cerebral blood flow in health and disease remain unclear. Methods: We systematically reviewed and synthesised data from studies examining changes in cerebral blood flow in healthy participants and patients with traumatic brain injury and critical illness. Results: Twenty‐eight eligible studies were included. In healthy subjects and patients without critical illness or traumatic brain injury, noradrenaline did not significantly change cerebral blood flow velocity (‐1.7%, 95%CI ‐4.7–1.3%) despite a 24.1% (95%CI 19.4–28.7%) increase in mean arterial pressure. In patients with traumatic brain injury, noradrenaline significantly increased cerebral blood flow velocity (21.5%, 95%CI 11.0–32.0%), along with a 33.8% (95%CI 14.7–52.9%) increase in mean arterial pressure. In patients who were critically ill, noradrenaline significantly increased cerebral blood flow velocity (20.0%, 95%CI 9.7–30.3%), along with a 32.4% (95%CI 25.0–39.9%) increase in mean arterial pressure. Our analyses suggest intact cerebral autoregulation in healthy subjects and patients without critical illness or traumatic brain injury., and impaired cerebral autoregulation in patients with traumatic brain injury and who were critically ill. The extent of mean arterial pressure changes and the pre‐treatment blood pressure levels may affect the magnitude of cerebral blood flow changes. Studies assessing cerebral blood flow using non‐transcranial Doppler methods were inadequate and heterogeneous in enabling meaningful meta‐analysis. Conclusions: Noradrenaline significantly increases cerebral blood flow in humans with impaired, not intact, cerebral autoregulation, with the extent of changes related to the severity of functional impairment, the extent of mean arterial pressure changes and pre‐treatment blood pressure levels. [ABSTRACT FROM AUTHOR]

To analyze the correlation of carotid stenosis severity, the Plaque Reporting and Data System (RADS) score, arterial transit artifacts (ATAs), and cerebral blood flow (CBF) with clinical cerebral ischemic symptoms in patients with carotid artery stenosis (CAS). Sixty-one patients with unilateral internal carotid artery stenosis or occlusion (≥50% stenosis) diagnosed by ultrasound, Computed Tomography(CT) angiography, or Magnetic Resonance(MR) angiography in Yichang City Central People's Hospital from January 2022 to February 2024 were retrospectively enrolled and divided into two groups according to the presence or absence of symptoms. Both groups underwent MR plaque imaging and arterial spin labeling (ASL)-based 3.0 T MRI to compare the differences in stenosis degree, Plaque-RADS score, ATA grade, and CBF between the two groups. Binary regression analysis was used to identify the parameters with statistically significant differences between the two groups and to evaluate their diagnostic efficacy using the area under the workup curve of the subjects. The Plaque-RADS score, ATA grade, and CBF differences in the anterior cerebral artery(ACA)blood supply region were correlated with symptoms, and the areas under the ROC curves for the CBF differences in the ACA blood supply region, Plaque-RADS score, ATA grade and a joint model that combines all three to predict symptoms in CAS patients were 0.672, 0.796, 0.788 and 0.919, respectively. CBF, Plaque-RADS and ATAs were identified as independent risk factors for symptoms in patients with CAS and have a certain predictive value for symptoms, and the combined predictive value is greater, potentially providing a more effective imaging modality for clinical treatment and evaluation. • Arterial Transit Artifacts were found to be associated with cerebral ischemia symptoms. • The combination of Plaque-RADS and Arterial Transit Artifacts in predicting symptoms has a higher predictive value. • The PLD used for ASL scanning in this study was 2.0 s, further confirming the broad applicability of our results. [ABSTRACT FROM AUTHOR]

Bispectral index with density spectral array (BIS-DSA) monitoring during hyperbaric oxygen therapy of a case with inner ear and cerebral decompression sickness is described. During the initial treatment, a particular DSA pattern was found, which resolved after four treatments. Clinical resolution of the symptoms accompanied this improvement. The particular BIS-DSA pattern described in this case is concordant with a potential hypo-perfusion of the cortex related to decompression stress. This case suggests that BIS-DSA monitoring may be an easy, cost-effective, and viable form of neuro-monitoring during hyperbaric oxygen treatment for decompression sickness. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to identify the cerebral physiologic response to aerobic exercise in individuals with a symptomatic concussion, highlighting available knowledge and knowledge gaps in the literature. Design: A systematic scoping review was conducted and reported in keeping with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews. A search of EMBASE, MEDLINE, SCOPUS, BIOSIS, and Cochrane libraries was conducted on June 15, 2023 (from database inception). An online systematic/scoping review management system was used to remove duplicates, and the remaining articles were screened for inclusion by 2 researchers. Inclusion criteria required articles to be original research published in peer- reviewed journals. Additionally, studies were required to have an aerobic exercise component, include a measure of cerebral physiology during a bout of aerobic exercise, exclude moderate and/or severe traumatic brain injury (TBI) populations, and be in the English language. Both human and animal studies were included, with participants of any age who were diagnosed with a mild TBI/concussion only (ie, Glasgow Coma Scale score ≥ 13). Studies could be of any design as long as a measure of cerebral physiologic response to a bout of aerobic exercise was included. Results: The search resulted in 1773 articles to be screened and data from 3 eligible studies were extracted. Conclusions: There are currently too few studies investigating the cerebral physiologic response to aerobic exercise following concussion or mild TBI to draw definitive conclusions. Further research on this topic is necessary since understanding the cerebral physiologic response to aerobic exercise in the concussion and mild TBI populations could assist in optimizing exercise-based treatment prescription and identifying other targeted therapies. [ABSTRACT FROM AUTHOR]