Recent Submissions

  • Putamen iron quantification in diseases with neurodegeneration: a meta-analysis of the quantitative susceptibility mapping technique

    Fatehi, Farzad (2024-05-17)
    Quantitative susceptibility mapping (QSM) is an MRI technique that accurately measures iron concentration in brain tissues. This meta-analysis synthesized evidence from 30 studies that used QSM to quantify the iron levels in the putamen. The PRISMA statement was adhered to when conducting the systematic reviews and meta-analyses. We conducted a meta-analysis using a random-effects model, as well as subgroup analyses (disease type, geographic region, field strength, coil, disease type, age, and sex) and sensitivity analysis. A total of 1247 patients and 1035 controls were included in the study. Pooled results showed a standardized mean difference (SMD) of 0.41 (95% CI 0.19 to 0.64), with the strongest effect seen in Alzheimer's disease (AD) at 1.01 (95% CI 0.50 to 1.52). Relapsing-remitting multiple sclerosis (RRMS) also showed increased putaminal iron at 0.37 (95% CI 0.177 to 0.58). No significant differences were observed in Parkinson's disease (PD). No significant differences were found between subgroups based on geographic region, field strength, coil, disease type, age, and sex. The studies revealed significant heterogeneity, with field strength as the primary source, while other factors, such as disease type, location, age, sex, and coil type, may have contributed. The sensitivity analysis showed that these factors did not have a significant influence on the overall results. In summary, this meta-analysis supports abnormalities in putaminal iron content across different diseases with neurodegeneration, especially AD and RRMS, as measured by QSM. This highlights the potential of QSM as an imaging biomarker to better understand disease mechanisms involving disturbances in brain iron homeostasis.
  • Tertiary centre study highlights low inpatient deintensification and risks associated with adverse outcomes in frail people with diabetes

    Aftab, Faseeha; Fazil, Mohamed; Gallagher, Alison; Higgins, Kath; Lwin, Huin; Melson, Eka; Thomas, Anu; Thottungal, Kevin; Tun, HayMar (2024-03)
    Introduction: The community deintensification rates in older people with diabetes are low and hospital admission presents an opportunity for medication review. We audited the inpatient assessment and deintensification rate in people with diabetes and frailty. We also identified factors associated with adverse inpatient outcomes. Methods: A retrospective review of electronic charts was conducted in all people with diabetes and clinical frailty score ≥6 who were discharged from the medical unit in 2022. Data on demographics, comorbidities and background glucose-lowering medications were collected. Results: Six-hundred-and-sixty-five people with diabetes and moderate/severe frailty were included in our analysis. For people with no HbA1c in the last six months preceding admission, only 9.0% had it assessed during inpatient. Deintensification rates were 19.1%. Factors that were associated with adverse inpatient outcomes included inpatient hypoglycaemia, non-White ethnicity, and being overtreated (HbA1c <7.0% [53 mmol/mol] with any glucose-lowering medication). Conclusion: The assessment and deintensification rate in secondary care for people with diabetes and frailty is low. Inpatient hypoglycaemia, non-White ethnicity, and overtreatment are important factors in determining inpatient outcomes highlighting the importance of deintensification and the need for an evidence-based risk stratification tool.
  • Early and 1-year mortality of native geriatric distal femur fractures: A systematic review and time-to-event meta-analysis

    Srinivasan, Ananth (2024-02-23)
    Purpose: Distal femur fractures (DFF) account for 6% of all femoral fractures and predominate in females. The current 1-year mortality of DFF is currently reported to be between 10 and 38%, a wide margin, and confounded by multiple factors including age, high energy mechanisms, pathological and periprosthetic fractures. The purpose of this study was to assess and determine all-cause mortality following geriatric native distal femur fractures at 30 days, six months and one year. Methods: - The databases Cochrane CENTRAL, MEDLINE, EMBASE and NHS NICE Healthcare Databases Advanced Search Interface were searched in accordance with PRISMA guidelines. Original research articles relevant to mortality outcomes in native geriatric distal femur fractures following low energy trauma were included. A time-to-event data meta-analysis model was used to estimate pooled 30-day, six month and one-year mortality. A random effects meta-regression model was performed to assess potential sources of heterogeneity when studies reported on factors affecting the mortality observed in patients with geriatric distal femur fractures. Results: - Thirteen studies were included in the meta-analysis with a mean age of 79.6 years. Eight studies reported the 30-day mortality of distal femur fractures in patients as a pooled estimate of 8.14%. Pooled estimate for 6-month mortality reported was 19.5% and the one-year mortality reported by ten studies was 26.10%. Time-to-event modelling showed that risk of mortality at one year in elderly patients with distal femur fractures was significantly higher HR = 4.31 (p < 0.001). When evaluating prognostic predictors, age and Type C fracture were predictive of highest mortality rates. Conclusions: - This study is the first meta-analysis to evaluate the early and long-term mortality observed in elderly patients presenting with native distal femoral fractures. Through our results we have shown the quantifiable impact patient age and fracture configuration has on one-year mortality in this patient cohort.
  • Participatory translational science of neurodivergence: model for attention-deficit/hyperactivity disorder and autism research

    Balwani, Beta (2024-02-16)
    Background: There are increasing calls for neurodivergent peoples' involvement in research into neurodevelopmental conditions. So far, however, this has tended to be achieved only through membership of external patient and public involvement (PPI) panels. The Regulating Emotions - Strengthening Adolescent Resilience (RE-STAR) programme is building a new participatory model of translational research that places young people with diagnoses of attention-deficit hyperactivity disorder (ADHD) and autism at the heart of the research team so that they can contribute to shaping and delivering its research plan. Aims: To outline the principles on which the RE-STAR participatory model is based and describe its practical implementation and benefits, especially concerning the central role of members of the Youth Researcher Panel (Y-RPers). Method: The model presented is a culmination of a 24-month process during which Y-RPers moved from advisors to co-researchers integrated within RE-STAR. It is shaped by the principles of co-intentionality. The account here was agreed following multiple iterative cycles of collaborative discussion between academic researchers, Y-RPers and other stakeholders. Results: Based on our collective reflections we offer general guidance on how to effectively integrate young people with diagnoses of ADHD and/or autism into the core of the translational research process. We also describe the specific theoretical, methodological and analytical benefits of Y-RPer involvement in RE-STAR. Conclusions: Although in its infancy, RE-STAR has demonstrated the model's potential to enrich translational science in a way that can change our understanding of the relationship between autism, ADHD and mental health. When appropriately adapted we believe the model can be applied to other types of neurodivergence and/or mental health conditions.
  • Point-of-care ultrasound is a useful adjunct tool to a clinician's assessment in the evaluation of severe hyponatraemia

    Al Alaisi, Salam; Coats, Timothy; Levy, Miles; Melson, Eka; Rahman, Faizanur; Rahman, Latif; Reddy, Narendra; Sardar, Muhammad; Shafiq, Shahriar (2024-01-16)
    Introduction: Hyponatraemia is the most common electrolyte disorder in inpatients resulting mainly from an imbalance in water homeostasis. Intravascular fluid status assessment is pivotal but is often challenging given multimorbidity, polypharmacy and diuretics use. We evaluated the utility of point-of-care ultrasound (POCUS) as an adjunct tool to standard practice for fluid assessment in severe hyponatraemia patients. Methods: Patients presenting with severe hyponatremia (Serum Sodium [Na] < 120 mmol/L; Normal range: 135-145 mol/L), managed by standard care were included. Hyponatraemia biochemistry work-up and POCUS examination were undertaken. Both clinician and POCUS independently assigned one of the three fluid status groups of hypovolaemia, hypervolaemia or euvolaemia. The final diagnosis of three fluid status groups at admission was made at the time of discharge by retrospective case review. Clinician's (standard of care) and POCUS fluid assessments were compared to that of the final diagnosis at the time of discharge. Results: n = 19 patients were included. Median Na on admission was 113 mmol/L (109-116), improved to 129 ± 3 mmol/L on discharge. POCUS showed the higher degree of agreement with the final diagnosis (84%; n = 16/19), followed by the clinician (63%; n = 12/19). A trend towards higher accuracy of POCUS compared to clinician assessment of fluid status was noted (84% vs. 63%, p = 0.1611). Biochemistry was unreliable in 58% (n = 11/19) likely due to renal failure, polypharmacy or diuretic use. Inappropriate emergency fluid management was undertaken in 37% (n = 7/19) of cases based on initial clinician assessment. Thirst symptom correlated to hypovolaemia in 80% (4/5) cases. Conclusion: As subjective clinical and biochemistry assessments of fluid status are often unreliable due to co-morbidities and concurrent use of medications, POCUS can be a rapid objective diagnostic tool to assess fluid status in patients with severe hyponatraemia, to guide accurate emergency fluid management.
  • A syndromic neurodevelopmental disorder caused by rare variants in PPFIA3

    Vasudevan, Pradeep (2024-01-04)
    PPFIA3 encodes the protein-tyrosine phosphatase, receptor-type, F-polypeptide-interacting-protein-alpha-3 (PPFIA3), which is a member of the LAR-protein-tyrosine phosphatase-interacting-protein (liprin) family involved in synapse formation and function, synaptic vesicle transport, and presynaptic active zone assembly. The protein structure and function are evolutionarily well conserved, but human diseases related to PPFIA3 dysfunction are not yet reported in OMIM. Here, we report 20 individuals with rare PPFIA3 variants (19 heterozygous and 1 compound heterozygous) presenting with developmental delay, intellectual disability, hypotonia, dysmorphisms, microcephaly or macrocephaly, autistic features, and epilepsy with reduced penetrance. Seventeen unique PPFIA3 variants were detected in 18 families. To determine the pathogenicity of PPFIA3 variants in vivo, we generated transgenic fruit flies producing either human wild-type (WT) PPFIA3 or five missense variants using GAL4-UAS targeted gene expression systems. In the fly overexpression assays, we found that the PPFIA3 variants in the region encoding the N-terminal coiled-coil domain exhibited stronger phenotypes compared to those affecting the C-terminal region. In the loss-of-function fly assay, we show that the homozygous loss of fly Liprin-α leads to embryonic lethality. This lethality is partially rescued by the expression of human PPFIA3 WT, suggesting human PPFIA3 function is partially conserved in the fly. However, two of the tested variants failed to rescue the lethality at the larval stage and one variant failed to rescue lethality at the adult stage. Altogether, the human and fruit fly data reveal that the rare PPFIA3 variants are dominant-negative loss-of-function alleles that perturb multiple developmental processes and synapse formation.
  • The effect of hypercapnia on the directional sensitivity of dynamic cerebral autoregulation and the influence of age and sex

    Clough, Rebecca; Beishon, Lucy; Robinson, Thompson; Davies, Aaron; Minhas, Jatinder S (2023-09-25)
    The cerebral circulation responds differently to increases in mean arterial pressure (MAP), compared to reductions in MAP. We tested the hypothesis that this directional sensitivity is reduced by hypercapnia. Retrospective analysis of 104 healthy subjects (46 male (44%), age range 19-74 years), with five minute recordings of middle cerebral blood velocity (MCAv, transcranial Doppler), non-invasive MAP (Finometer) and end-tidal CO2 (capnography) at rest, during both poikilocapnia and hypercapnia (5% CO2 breathing in air) produced MCAv step responses allowing estimation of the classical Autoregulation Index (ARIORIG), and corresponding values for both positive (ARI+D) and negative (ARI-D) changes in MAP. Hypercapnia led to marked reductions in ARIORIG, ARI+D and ARI-D (p < 0.0001, all cases). Females had a lower value of ARIORIG compared to males (p = 0.030) at poikilocapnia (4.44 ± 1.74 vs 4.74 ± 1.48) and hypercapnia (2.44 ± 1.93 vs 3.33 ± 1.61). The strength of directional sensitivity (ARI+D-ARI-D) was not influenced by hypercapnia (p = 0.46), sex (p = 0.76) or age (p = 0.61). During poikilocapnia, ARI+D decreased with age in females (p = 0.027), but not in males. Directional sensitivity was not affected by hypercapnia, suggesting that its origins are more likely to be inherent to the mechanics of vascular smooth muscle than to myogenic pathways.
  • The use of culturally adapted and translated depression screening questionnaires with South Asian haemodialysis patients in England

    Warwick, Graham (2023-04-07)
    Background: Depression is common amongst patients receiving haemodialysis (HD). Assessment and intervention when faced with language and cultural barriers is challenging. To support clinician decisions, we conducted a cross-sectional study to assess the use of culturally adapted and translated versions of commonly-used depression screening questionnaires with South Asian patients receiving HD in England. Methods: Patients completed adapted versions of the Patient Health Questionnaire (PHQ-9), the Centre for Epidemiological Studies Depression Scale Revised (CESD-R), and the Beck Depression Inventory II (BDI-II). All questionnaires were available in Gujarati, Punjabi, Urdu, and Bengali. A comparative sample of white-Europeans completed the questionnaires in English. The research was based across 9 National Health Service (NHS) Trusts in England. Structural validity of translated questionnaires was assessed using confirmatory factor analysis. Diagnostic accuracy was explored in a subgroup of South Asians against ICD-10 categories using the Clinical Interview Schedule Revised (CIS-R) with receiver operating curve (ROC) analysis. Results: 229 South Asian and 120 white-European HD patients participated. A single latent depression factor largely accounted for the correlations between items of the PHQ-9, CESD-R and BDI-II. Issues with measurement equivalence implied that scores on the translations may not be comparable with the English language versions. Against CIS-R based ICD-10 diagnosis of depression, sensitivity was modest across scales (50-66.7%). Specificity was higher (81.3-93.8%). Alternative screening cut-offs did not improve positive predictive values. Conclusions: Culturally adapted translations of depression screening questionnaires are useful to explore symptom endorsement amongst South Asian patients. However, data indicate that standard cut-off scores may not be appropriate to classify symptom severity. Use of the CIS-R algorithms for optimal case identification requires further exploration in this setting. Strategies to encourage recruitment of under-represented groups in renal research are also warranted, especially for in-depth discussions related to psychological care needs.
  • Altered visual conscious awareness in patients with vestibular dysfunctions; a cross-sectional observation study

    Saman, Yougan; Rea, Peter (2023-03-21)
    Background: Patients with vestibular dysfunctions often experience visual-induced symptoms. Here we asked whether such visual dependence can be related to alterations in visual conscious awareness in these patients. Methods: To measure visual conscious awareness, we used the effect of motion-induced blindness (MIB,) in which the perceptual awareness of the visual stimulus alternates despite its unchanged physical characteristics. In this phenomenon, a salient visual target spontaneously disappears and subsequently reappears from visual perception when presented against a moving visual background. The number of perceptual switches during the experience of the MIB stimulus was measured for 120 s in 15 healthy controls, 15 patients with vestibular migraine, 15 patients with benign positional paroxysmal vertigo (BPPV) and 15 with migraine without vestibular symptoms. Results: Patients with vestibular dysfunctions (i.e., both vestibular migraine and BPPV) exhibited increased perceptual fluctuations during MIB compared to healthy controls and migraine patients without vertigo. In VM patients, those with more severe symptoms exhibited higher fluctuations of visual awareness (i.e., positive correlation), whereas, in BPPV patients, those with more severe symptoms had lower fluctuations of visual awareness (i.e., negative correlation). Implications: Taken together, these findings show that fluctuations of visual awareness are linked to the severity of visual-induced symptoms in patients with vestibular dysfunctions, and distinct pathophysiological mechanisms may mediate visual vertigo in peripheral versus central vestibular dysfunctions.
  • A late and complex presentation of hereditary haemochromatosis

    Anand, Preethu; Ghaly, George (2022-11-29)
    We report a case of a 78-year-old male with a complex presentation that first diverted our attention from the underlying hereditary haemochromatosis (HH). A fit patient who initially came with leg pain and eventually died within 3 months of presenting with several syndromes relatable to HH that uncommonly manifest together. His initial presentation was pyomyositis in the thigh muscles followed by a diagnosis of myelodysplasia - refractory anaemia with excess blasts (RAEB), congestive cardiac failure and liver abscesses. End-stage heart failure and recurrent infections were the main causes of the patient's death prior to trials of specific treatment for HH. Recurrent atypical infections and myelodysplastic syndrome (MDS) should raise alarms for iron overload. In HH there can be a rapid progression of the disease process resulting in nearly irreversible organopathy, thus impeding treatment trials. Early detection and reduction of iron overload may reduce morbidity and mortality.
  • Age-related differences in cerebrovascular responses to cognitive stimulation using a novel method

    Robinson, Thompson
    Aging is associated with a number of alterations to cerebrovascular function. We aimed to investigate the effect of age on cerebrovascular responses to cognitive stimulation using an objective two-parameter method.Previously derived from a large data-set (135 healthy participants) were applied to a task-activated dataset of 69 healthy participants in five different task conditions. Cumulative response rate (CRR) was calculated as the sum of responses across tasks and hemispheres.There was a significant effect of age (adjusted odds ratio: 1.02 (95% confidence interval: 1.01, 1.04), p = 0.016). There was also a significant effect of task (p = 0.002), but there was no significant interaction between age and task (p = 0.37). Increasing age was associated with increased CRR (adjusted odds ratio: 1.04 (95% confidence interval: 1.01, 1.07), p = 0.009).Using an objective two-parameter method, healthy older adults had increased cerebrovascular responses to cognitive testing.
  • Moderate-intensity stepping in older adults: insights from treadmill walking and daily living

    Henson, Joseph; Herring, Louisa; Sargeant, Jack; Davies, Melanie; Dempsey, Paddy C (2023-03-18)
    Background: A step cadence of 100 steps/minute is widely used to define moderate-intensity walking. However, the generalizability of this threshold to different populations needs further research. We investigate moderate-intensity step cadence values during treadmill walking and daily living in older adults. Methods: Older adults (≥ 60 years) were recruited from urban community venues. Data collection included 7 days of physical activity measured by an activPAL3™ thigh worn device, followed by a laboratory visit involving a 60-min assessment of resting metabolic rate, then a treadmill assessment with expired gas measured using a breath-by-breath analyser and steps measured by an activPAL3™. Treadmill stages were undertaken in a random order and lasted 5 min each at speeds of 1, 2, 3, 4 and 5 km/h. Metabolic equivalent values were determined for each stage as standardised values (METSstandard) and as multiples of resting metabolic rate (METSrelative). A value of 3 METSstandard defined moderate-intensity stepping. Segmented generalised estimating equations modelled the association between step cadence and MET values. Results: The study included 53 participants (median age = 75, years, BMI = 28.0 kg/m2, 45.3% women). At 2 km/h, the median METSstandard and METSrelative values were above 3 with a median cadence of 81.00 (IQR 72.00, 88.67) steps/minute. The predicted cadence at 3 METSstandard was 70.3 (95% CI 61.4, 75.8) steps/minute. During free-living, participants undertook median (IQR) of 6988 (5933, 9211) steps/day, of which 2554 (1297, 4456) steps/day were undertaken in continuous stepping bouts lasting ≥ 1 min. For bouted daily steps, 96.4% (90.7%, 98.9%) were undertaken at ≥ 70 steps/minute. Conclusion: A threshold as low as 70 steps/minute may be reflective of moderate-intensity stepping in older adults, with the vast majority of all bouted free-living stepping occurring above this threshold.
  • The scalability of common paradigms for assessment of cognitive function: A functional transcranial Doppler study

    Robinson, Thompson (2022-03-28)
    Cognitive paradigms induce changes in cerebral blood flow (CBF) associated with increased metabolic demand, namely neurovascular coupling (NVC). We tested the hypothesis that the effect of complexity and duration of cognitive paradigms will either enhance or inhibit the NVC response. Bilateral CBF velocity (CBFV) in the middle cerebral arteries (MCAs) via transcranial Doppler ultrasound (TCD), blood pressure (BP), electrocardiogram (ECG) and end-tidal CO2 (EtCO2) of 16 healthy participants (aged 21-71 years) were simultaneously recorded at rest and during randomized paradigms of different complexities (naming words beginning with P-,R-,V- words and serial subtractions of 100-2,100-7,1000-17), and durations (5s, 30s and 60s). CBFV responses were population mean normalized from a 30-s baseline period prior to task initiation. A significant increase in bilateral CBFV response was observed at the start of all paradigms and provided a similar pattern in most responses, irrespective of complexity or duration. Although significant inter-hemispherical differences were found during performance of R-word and all serial subtraction paradigms, no lateralisation was observed in more complex naming word tasks. Also, the effect of duration was manifested at late stages of 100-7, but not for other paradigms. CBFV responses could not distinguish different levels of complexity or duration with a single presentation of the cognitive paradigm. Further studies of the ordinal scalability of the NVC response are needed with more advanced modelling techniques, or different types of neural stimulation.
  • Cerebrovascular responses to somatomotor stimulation in Parkinson's disease: A multivariate analysis

    Beishon, Lucy; Robinson, Thompson
    Parkinson's disease (PD) is a common neurodegenerative disorder, yet little is known about cerebral haemodynamics in this patient population. Previous studies assessing dynamic cerebral autoregulation (dCA), neurovascular coupling (NVC) and vasomotor reactivity (VMR) have yielded conflicting findings. By using multi-variate modelling, we aimed to determine whether cerebral blood flow (CBF) regulation is impaired in PD patients.55 healthy controls (HC) and 49 PD patients were recruited. PD subjects underwent a second recording following a period of abstinence from their anti-Parkinsonian medication. Continuous bilateral transcranial Doppler in the middle cerebral arteries, beat-to-beat mean arterial blood pressure (MAP; Finapres), heart rate (HR; electrocardiogram), and end-tidal CO2 (EtCO2; capnography) were measured. After a 5-min baseline period, a passive motor paradigm comprising 60 s of elbow flexion was performed. Multi-variate modelling quantified the contributions of MAP, ETCO2 and neural stimulation to changes in CBF velocity (CBFV). dCA, VMR and NVC were quantified to assess the integrity of CBF regulation.Neural stimulation was the dominant input. dCA, NVC and VMR were all found to be impaired in the PD population relative to HC (p < 0.01, p = 0.04, p < 0.01, respectively). Our data suggest PD may be associated with depressed CBF regulation. This warrants further assessment using different neural stimuli.
  • Antihypertensives in dementia: Good or bad for the brain?

    Beishon, Lucy
    Hypertension is associated with both ageing and dementia. Despite this, optimal blood pressure targets in dementia remain unclear. Both high and low blood pressure are associated with poorer cognition. Changes in vascular physiology in dementia may increase the vulnerability of the brain to hypoperfusion associated with antihypertensives. We discuss the potential risks of antihypertensives in the context of altered cerebral haemodynamics, and evidence from antihypertensive trials in dementia. We suggest that individualised blood pressure targets should be the focus for antihypertensive therapy in dementia, rather than strict control to uniform targets extrapolated from trials in cognitively healthy individuals.
  • Living with frailty and haemodialysis: a qualitative study

    Young, Hannah; Ruddock, Nicki; Harrison, Mary; Singh, Sally (2022-07-22)
    Background: Frailty is highly prevalent in people receiving haemodialysis (HD) and is associated with poor outcomes. Understanding the lived experiences of this group is essential to inform holistic care delivery. Methods: Semi-structured interviews with N = 25 prevalent adults receiving HD from 3 HD units in the UK. Eligibility criteria included a Clinical Frailty Scale (CFS) score of 4-7 and a history of at least one fall in the last 6 months. Sampling began guided by maximum variation sampling to ensure diversity in frailty status; subsequently theoretical sampling enabled exploration of preliminary themes. Analysis was informed by constructivist grounded theory; later we drew upon the socioecological model. Results: Participants had a mean age of 69 ± 10 years, 13 were female, and 13 were White British. 14 participants were vulnerable or mildly frail (CFS 4-5), and 11 moderately or severely frail (CFS 6-7). Participants characterised frailty as weight loss, weakness, exhaustion, pain and sleep disturbance arising from multiple long-term conditions. Participants' accounts revealed: the consequences of frailty (variable function and psychological ill-health at the individual level; increasing reliance upon family at the interpersonal level; burdensome health and social care interactions at the organisational level; reduced participation at the community level; challenges with financial support at the societal level); coping strategies (avoidance, vigilance, and resignation); and unmet needs (overprotection from family and healthcare professionals, transactional health and social care exchanges). Conclusions: The implementation of a holistic needs assessment, person-centred health and social care systems, greater family support and enhancing opportunities for community participation may all improve outcomes and experience. An approach which encompasses all these strategies, together with wider public health interventions, may have a greater sustained impact. Trial registration: ISRCTN12840463.
  • The role of the autonomic nervous system in cerebral blood flow regulation in dementia: A review

    Minhas, Jatinder S (2022-05-01)
    In this review we will examine the role of the autonomic nervous system in the control of cerebral blood flow (CBF) in dementia. Worldwide, 55 million people currently live with dementia, and this figure will increase as the global population ages. Understanding the changes in vascular physiology in dementia could pave the way for novel therapeutic approaches. Reductions in CBF have been demonstrated in multiple dementia sub-types, in addition to increased cerebrovascular resistance and reduced vasoreactivity. Cerebral autoregulation (CA) is a key mechanism for the maintenance of cerebral perfusion, but remains largely intact in cognitive disorders, despite reductions in global and regional CBF. However, the tight coupling between neuronal activity and CBF (neurovascular coupling - NVC) is lost in dementia, which may be a key driver of cognitive dysfunction. Despite numerous studies investigating disturbances in the control of CBF in dementia, less is known about the specific mechanisms responsible for the observed changes. Disturbances could be related to one of a number of pathways and mechanisms including disruption of the autonomic component. In this review we will explore clinical and animal studies, which specifically investigated the autonomic component of CBF control in dementia, drawing on the clinical implications and potential for novel biomarker and therapeutic targets.
  • The cognitive basis of psychosocial impact in COVID-19 pandemic. Does it encircle the default mode network of the brain? A pragmatic proposal

    Mitchell, Alex J
    Epigenetics, hypothalamic-pituitary axes, environmental and metabolic influences, and transgenerational plasticity govern social behavior. Cognitive research considers the brain's default mode network (DMN) as a central hub that integrates various cognitive and social processing domains responsible for emotion perception, empathy, theory of mind, and morality. Hence, DMN is regarded as the "social brain." Upsurge in social turmoil, social anxiety, panic, depression, post-traumatic stress, hoarding, herd behavior, substance and behavioral addictions, sexual abuse, and violence in the time of the COVID-19 pandemic are intricately related to personality traits resulting in disruptive social cognition and social behavior, conceptualized as the result of unsettling and disruption of the functional nexus of the DMN. Considering overt and conspicuous display of neuroticism during the current pandemic, its impact upon modulation of the DMN functional nexus and the DMN itself, and the potential to presage cognitive impairment in the future, the authors caution that an increase in the global burden of dementia may be one of the long-term ramifications of COVID-19. Social behavior, a functional derivative of the DMN, can strikingly affect the functional nexus of DMN and the DMN itself, in a centripetal way via the phenomenon called "Experience-Dependent Plasticity," with long-term consequences. In this review, we intend to 1) decipher the association between social cognition and social behavior with the DMN, in time of COVID-19; and to 2) discuss the prospective aftermath of disrupted social behavior during the pandemic on modulation/alteration of functional connectomes of DMN or the DMN itself in the time ahead.

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