The human ability to flexibly alternate between tasks represents a central component of cognitive control. Neuroimaging studies have linked task switching with a diverse set of prefrontal cortex ...(PFC) regions, but the contributions of these regions to various forms of cognitive flexibility remain largely unknown. Here, subjects underwent functional brain imaging while they completed a paradigm that selectively induced stimulus, response, or cognitive set switches in the context of a single task decision performed on a common set of stimuli. Behavioral results indicated comparable reaction time costs associated with each switch type. Domain-general task-switching activation was observed in the inferior frontal junction and posterior parietal cortex, suggesting core roles for these regions in switching such as updating and representing task sets. In contrast, multiple domain-preferential PFC activations were observed across lateral and medial PFC, with progressively more rostral regions recruited as switches became increasingly abstract. Specifically, highly abstract cognitive set switches recruited anterior-PFC regions, moderately abstract response switches recruited mid-PFC regions, and highly constrained stimulus switches recruited posterior-PFC regions. These results demonstrate a functional organization across lateral and medial PFC according to the level of abstraction associated with acts of cognitive flexibility.
The purpose of this study was to examine the effect of regular exercise training on insulin sensitivity in adults with type 2 diabetes mellitus (T2DM) using the pooled data available from randomised ...controlled trials. In addition, we sought to determine whether short-term periods of physical inactivity diminish the exercise-induced improvement in insulin sensitivity. Eligible trials included exercise interventions that involved ≥3 exercise sessions, and reported a dynamic measurement of insulin sensitivity. There was a significant pooled effect size (ES) for the effect of exercise on insulin sensitivity (ES, -0.588; 95% confidence interval CI, -0.816 to -0.359; P<0.001). Of the 14 studies included for meta-analyses, nine studies reported the time of data collection from the last exercise bout. There was a significant improvement in insulin sensitivity in favour of exercise versus control between 48 and 72 hours after exercise (ES, -0.702; 95% CI, -1.392 to -0.012; P=0.046); and this persisted when insulin sensitivity was measured more than 72 hours after the last exercise session (ES, -0.890; 95% CI, -1.675 to -0.105; P=0.026). Regular exercise has a significant benefit on insulin sensitivity in adults with T2DM and this may persist beyond 72 hours after the last exercise session.
Previous reports have noted cerebrovascular regulation differs across the cardiac cycle, with greater regulation occurring within systole. However, this methodological notion has not been ...meticulously scrutinized during temporally deduced neurovascular coupling (NVC) metrics with additional respect to biological sex. Analyses of 111 healthy individuals (40 females/71 males) were performed where participants engaged in the "Where's Waldo?" paradigm. All NVC parameters were quantified in the posterior and middle cerebral arteries at 310 unique timepoints. Several individuals completed repeat testing which enabled for between-day (3 timepoints) and within-day (7 timepoints) reliability comparisons in 17 and 11 individuals, respectively. One-way analysis of variance compared NVC metrics between diastole, mean, and systole values, as well as differences between biological sexes. Greater absolute cerebral blood velocity (CBv; baseline and peak) and total activation (area under the curve) were noted within systole for both posterior cerebral artery (PCA;
< 0.001) and middle cerebral artery (MCA;
< 0.001) values; however, the relative percent increase in CBv was greater within diastole (
< 0.001). Females had an elevated diastolic and mean CBv and a greater diastolic cerebrovascular conductance (
< 0.050). No sex differences were present for systolic CBv measures and within parameters quantifying the NVC response (area under the curve/relative CBv increase) across the cardiac cycle (
> 0.072). Future investigations seeking to differentiate cerebral regulatory mechanisms between clinical populations may benefit by performing their analyses across the cardiac cycle, as certain pathogenesis may affect one aspect of the cardiac cycle independently. Minimal differences were noted between females and males for metrics characterizing the NVC response across the cardiac cycle.
Neurovascular coupling (NVC) studies commonly assess the mean cerebral hemodynamic response with little consideration for diastole, systole, and biological sex. Greater total activation expressed as the area under the curve was seen within systole compared with mean and diastole. Resting cerebral blood velocity sex differences were more prevalent during diastole when the cerebrovasculature was pressure-passive. Future studies should assess the NVC response across the cardiac cycle as it may help delineate the underlying pathophysiology of various clinical populations.
Climate change may constrain future electricity supply adequacy by reducing electric transmission capacity and increasing electricity demand. The carrying capacity of electric power cables decreases ...as ambient air temperatures rise; similarly, during the summer peak period, electricity loads typically increase with hotter air temperatures due to increased air conditioning usage. As atmospheric carbon concentrations increase, higher ambient air temperatures may strain power infrastructure by simultaneously reducing transmission capacity and increasing peak electricity load. We estimate the impacts of rising ambient air temperatures on electric transmission ampacity and peak per-capita electricity load for 121 planning areas in the United States using downscaled global climate model projections. Together, these planning areas account for roughly 80% of current peak summertime load. We estimate climate-attributable capacity reductions to transmission lines by constructing thermal models of representative conductors, then forcing these models with future temperature projections to determine the percent change in rated ampacity. Next, we assess the impact of climate change on electricity load by using historical relationships between ambient temperature and utility-scale summertime peak load to estimate the extent to which climate change will incur additional peak load increases. We find that by mid-century (2040-2060), increases in ambient air temperature may reduce average summertime transmission capacity by 1.9%-5.8% relative to the 1990-2010 reference period. At the same time, peak per-capita summertime loads may rise by 4.2%-15% on average due to increases in ambient air temperature. In the absence of energy efficiency gains, demand-side management programs and transmission infrastructure upgrades, these load increases have the potential to upset current assumptions about future electricity supply adequacy.
ObjectivesGreater arterial stiffness and poor 24h blood pressure (BP) are recognized as indicators of poor cardiovascular health. Evidence has shown that high intensity interval training (HIIT) may ...be a superior alternative to moderate intensity continuous training (MICT) for improving cardiovascular disease risk factors such as cardiorespiratory fitness and vascular function. However, there are limited data comparing the effect of HIIT to MICT on central arterial stiffness and/or 24h BP response. The purpose of this study was to compare HIIT versus MICT on central arterial stiffness and 24h BP outcomes by systematic review and meta-analysis.DesignA systematic review and meta-analysis was conducted.MethodsEligible studies were exercise training interventions (≥4weeks) that included both HIIT and MICT and reported central arterial stiffness, as measured by pulse wave velocity and augmentation index and/or 24h BP outcome measures.ResultsHIIT was found to be superior to MICT for reducing night-time diastolic BP (ES: −0.456, 95% CI: −0.826 to −0.086mmHg; P=0.016). A near-significant greater reduction in daytime systolic (ES: −0.349, 95% CI: −0.740 to 0.041mmHg; p=0.079) and diastolic BP was observed with HIIT compared to MICT (ES: −0.349, 95% CI: −0.717 to 0.020mmHg; p=0.063). No significant difference was found for other BP responses or arterial stiffness outcomes.ConclusionsHIIT leads to a superior reduction in night-time diastolic BP compared to MICT. Furthermore, a near-significant greater reduction in daytime BP was found with HIIT compared to MICT. No significant difference was observed for changes to central arterial stiffness between HIIT and MICT.
Histories of information help clarify the values and intellectual commitments of the discipline. This study takes a rhetorical history approach to better understand the development of information ...studies as a discipline. Information studies historians have identified that the Cold War period was critical for the development of information science and consequently of its modern‐day incarnations. Due to post‐World War II prosperity, the 1960s saw a surge in interest in scientific and technical information. Many from government, education, and private sectors took interest in developing new ways to compete with Soviet science. This interest led to the National Science Foundation (NSF)‐funded Georgia Tech conferences of 1961 and 1962, which are analyzed here. I find that concerns about the “science information problem” provided language that was critical for transforming some of the information studies’ central concepts. In particular, I find that the idea of an “information scientist” was made possible by national funding for science information. I suggest that attending to the discursive traffic between public and disciplinary discourse of information studies can better attune the field to its intellectual commitments.
Neuroimaging biomarkers that precede cognitive decline have the potential to aid early diagnosis of Alzheimer's disease (AD). A body of diffusion tensor imaging (DTI) work has demonstrated declines ...in white matter (WM) microstructure in AD and its typical prodromal state, amnestic mild cognitive impairment. The present review summarizes recent evidence suggesting that WM integrity declines are present in individuals at high AD-risk, prior to cognitive decline. The available data suggest that AD-risk is associated with WM integrity declines in a subset of tracts showing decline in symptomatic AD. Specifically, AD-risk has been associated with WM integrity declines in tracts that connect gray matter structures associated with memory function. These tracts include parahippocampal WM, the cingulum, the inferior fronto-occipital fasciculus, and the splenium of the corpus callosum. Preliminary evidence suggests that some AD-risk declines are characterized by increases of radial diffusivity, raising the possibility that a myelin-related pathology may contribute to AD onset. These findings justify future research aimed at a more complete understanding of the neurobiological bases of DTI-based declines in AD. With continued refinement of imaging methods, DTI holds promise as a method to aid identification of presymptomatic AD. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.
► Review focuses on diffusion tensor imaging (DTI) studies of normal subjects before symptoms of Alzheimer’s disease (AD). ► Summarizes risk factors of AD, and DTI methodology. ► Summarizes evidence that white matter (WM) integrity changes are present in normal persons at high-AD risk. ► These findings have the potential to aid early diagnosis of AD. ► Future research should determine if DTI changes reflect classic AD pathologies, or other WM pathologies.
The increasing recognition that fatty liver plays a direct role in the pathogenesis of cardiovascular and metabolic disease has resulted in significant research enquiry into the efficacy of lifestyle ...therapy in modulating liver fat. Recently, this has extended to the specific investigation of a possible independent benefit of physical activity/exercise in nonalcoholic fatty liver disease (NAFLD). In this article we review the effect of acute and regular exercise (training) on metabolism, including liver glucose and lipid metabolism, and the available human trials that have compared the benefit of regular exercise versus a nonexercise control on liver fat. The limited human research suggests that exercise can reduce liver fat and that this benefit may be mediated, in part, by a reduction in hepatic lipogenesis. The relative importance of extrahepatic adaptations and acute versus regular exercise in explaining this benefit are discussed. From a clinical perspective, the revelation of a benefit of exercise per se offers a novel approach for liver fat reduction, and highlights the importance of incorporating fitness assessment and prescription in the management of patients with fatty liver disorders. Implementation of exercise therapy in a clinical setting is arguably the biggest challenge because evidence shows that mere provision of information about the benefits of exercise and/or exercise prescription to the patient does not translate to positive outcomes. Rather, the focus should be on implementing strategies to promote behavior change including regular contact and assessment with a health care professional, self-monitoring, and personalization of goals that focus on changing physical activity behavior.
Volt-VAR and Volt-Watt functionality in photovoltaic (PV) smart inverters provide mechanisms to ensure system voltage magnitudes and power factors remain within acceptable limits. However, these ...control functions can become unstable, introducing oscillations in system voltages when not appropriately configured or maliciously altered during a cyberattack. In the event that Volt-VAR and Volt-Watt control functions in a portion of PV smart inverters in a distribution grid are unstable, the proposed adaptation scheme utilizes the remaining and stably-behaving PV smart inverters and other Distributed Energy Resources to mitigate the effect of the instability. The adaptation mechanism is entirely decentralized, model-free, communication-free, and requires virtually no external configuration. We provide a derivation of the adaptive control approach and validate the algorithm in experiments on the IEEE 37 and 8500 node test feeders.
Summary
Excess visceral adiposity contributes to elevated cardiometabolic risk, and waist circumference is commonly used as a surrogate measure of visceral adipose tissue. Although regular aerobic ...exercise is known to improve abdominal obesity, its effect on waist circumference is unclear. A systematic review and meta‐analysis was performed to determine (1) the effect of aerobic exercise on waist circumference in adults with overweight or obesity; (2) the association between any change in waist circumference and change in visceral adipose tissue and/or bodyweight with aerobic exercise interventions; and (3) if reductions in waist circumference with exercise are moderated by clinical characteristics or components of aerobic exercise prescription. Twenty‐five randomized controlled trials (1686 participants) were included. Regular aerobic exercise significantly reduced waist circumference by 3.2 cm (95% confidence interval CI −3.86, −2.51, p ≤ 0.001) versus control. Change in waist circumference was associated with change in visceral adipose tissue (β = 4.02; 95% CI 1.37, 6.66, p = 0.004), and vigorous intensity produced superior reduction (−4.2 cm, 95% CI −4.99, −3.42, p < 0.0001) in waist circumference compared with moderate intensity (−2.50 cm, 95% CI −3.22, −1.79, p = 0.058). These findings suggest regular aerobic exercise results in modest reductions in waist circumference and associated visceral adipose tissue and that higher intensity exercise may offer superior benefit to moderate intensity.
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