Abstract Some existing models of hippocampal function simulate performance in classical conditioning tasks using the error backpropagation algorithm to guide learning (Gluck, M.A., and Myers, C.E., ...(1993). Hippocampal mediation of stimulus representation: a computational theory. Hippocampus, 3(4), 491–516.). This algorithm is not biologically plausible because it requires information to be passed backward through layers of nodes and assumes that the environment provides information to the brain about what correct outputs should be. Here, we show that the same information-processing function proposed for the hippocampal region in the Gluck and Myers (1993) model can also be implemented in a network without using the backpropagation algorithm. Instead, our newer instantiation of the theory uses only (a) Hebbian learning methods which match more closely with synaptic and associative learning mechanisms ascribed to the hippocampal region and (b) a more plausible representation of input stimuli. We demonstrate here that this new more biologically plausible model is able to simulate various behavioral effects, including latent inhibition, acquired equivalence, sensory preconditioning, negative patterning, and context shift effects. In addition, the newer model is able to address some new phenomena including the effect of the number of training trials on blocking and overshadowing.
The latitudinal diversity gradient (LDG), where the number of species increases from the poles to the Equator, ranks among the broadest and most notable biodiversity patterns on Earth. The pattern of ...species-rich tropics relative to species-poor temperate areas has been recognized for well over a century, but the generative mechanisms are still debated vigorously. We use simulations to test whether spatio-temporal climatic changes could generate large-scale patterns of biodiversity as a function of only three biological processes-speciation, extinction and dispersal-omitting adaptive niche evolution, diversity-dependence and coexistence limits. In our simulations, speciation resulted from range disjunctions, whereas extinction occurred when no suitable sites were accessible to species. Simulations generated clear LDGs that closely match empirical LDGs for three major vertebrate groups. Higher tropical diversity primarily resulted from higher low-latitude speciation, driven by spatio-temporal variation in precipitation rather than in temperature. This suggests that spatio-temporal changes in low-latitude precipitation prompted geographical range disjunctions over Earth's history, leading to high rates of allopatric speciation that contributed to LDGs. Overall, we show that major global biodiversity patterns can derive from interactions of species' niches (fixed a priori in our simulations) with dynamic climate across complex, existing landscapes, without invoking biotic interactions or niche-related adaptations.
Glycemic control during and after exercise is challenging. APs reduce %<70 and TIR, but do not eliminate exercise-induced hypoglycemia. Recent work has shown that insulin reduction 90min prior to ...exercise may be optimal. We present the initial testing of an exercise-informed AP, able to anticipate regular exercise by up to 2h without user input. Eighteen adults with T1D were enrolled in a randomized crossover trial: 4-weeks data collection (DC: SAP+step counter) followed by two 32h supervised hotel stays (SH). During DC, participants were asked to exercise 4 times/week for >30min, between 4-7pm. During SH, participants used either a naïve AP (CTL) or exercise informed AP (EX) and participated in 45min of moderate exercise at 17:30 on day 1. Fifteen subjects completed the study, age 42.2±13.6, HbA1c 6.61±1.02, with no system related AEs. During exercise, EX and CTL had similar TIR 88.2 vs. 85.2%, with a tendency to less time <80mgdL, 14.8 vs. 8.2%, following a reduction of insulin from 2.4 to 1.8 U over the preceding 2h. Post exercise EX and CTL had similar TIR (87.2 vs. 85.5%) but EX had less %<70 1.1% vs. 8.9% p=0.04,overnight control was excellent in both case TIR: 98.1 vs. 99.4%; %<70: 0.1 vs. 0.6%. During the sedentary late afternoon (5-7pm day 2) there was no difference in TIR: 89.6 vs. 86.0%. APs can learn from prior exercise behaviors and anticipate them, potentially leading to reduced glycemic risk, and a more automated system.
Disclosure
J. Garcia-Tirado: None. S.A. Brown: Research Support; Self; Dexcom, Inc., Insulet Corporation, Roche Diabetes Care, Tandem Diabetes Care, Tolerion, Inc. N. Laichuthai: None. H.E. Myers: None. M.D. Breton: Research Support; Self; Dexcom, Inc., Novo Nordisk A/S, Sanofi, Tandem Diabetes Care. Speaker’s Bureau; Self; Dexcom, Inc., Tandem Diabetes Care.
Funding
National Institutes of Health (DP3DK106826)
In Alzheimer's disease (AD), amyloid-β (Aβ) pathology and intrinsic functional connectivity (iFC) interact. Across stages of AD, we expected individual spatial correspondence of Aβ and iFC to reveal ...both Aβ accumulation and its detrimental effects on iFC. We used resting-state functional magnetic imaging and Aβ imaging in a cross-sectional sample of 90 subjects across stages of AD and healthy older adults. Global and local correspondence of Aβ and iFC were assessed within the posterior default mode network (pDMN) by within-subject voxel-wise correlations. Beginning at preclinical stages, global Aβ-iFC correspondence was positive for the whole pDMN, showing that Aβ accumulates in areas of high connectivity, and reached a plateau at prodromal stages. Starting at preclinical stages, local correspondence was negative in network centers, indicating that Aβ reduces connectivity of the pDMN as a function of local plaque concentration, and peaked at prodromal stages. Positive global correspondence suggests that Aβ accumulation progresses along iFC, with this effect starting in preclinical stages, and being constant along clinical periods. Negative local correspondence suggests detrimental effects of Aβ on iFC in network centers, starting at preclinical stages, and peaking when first symptoms appear. Data reveal a complex trajectory of Aβ and iFC correspondence, affecting both Aβ accumulation and iFC impairments.
Background. The prevalence of fecal incontinence varies tremendously as a result of inadequate data collection methods. Few office-based studies have assessed the prevalence of fecal incontinence and ...none have looked at modifiable risk factors or effect on quality of life. Design, Settings, Patients, and Main Outcome Measures. Five hundred patients who visited our inner city, university-based gastroenterology practice, were asked about symptoms of fecal incontinence. We also retrospectively reviewed 500 charts to identify the frequency of patient-physician reporting of fecal incontinence. Results. Of the 500 patients that were directly questioned, 58 (12%, 43 women, 15 men) admitted to fecal incontinence compared to 12 (2.4%) in the retrospective arm. Patients with fecal incontinence and loose/watery stool reported the lowest quality of life scores. While the average severity score was similar between men and women, women had a significantly lower average quality of life score (3.04 versus 2.51; P<0.03). Conclusions. The identification of fecal incontinence increases when patients are directly questioned. Identifying and treating patients with loose stool is a potential strategy to improve quality of life in this patient population. In men and women with similar severity of fecal incontinence, women have a significantly lower quality of life.
Understanding the flow field around horizontal axis marine current turbines is important if this new energy generation technology is to advance. The aim of this work is to identify and provide an ...understanding of the principal parameters that govern the downstream wake structure and its recovery to the free-stream velocity profile. This will allow large farms or arrays of devices to be installed whilst maximising device and array efficiency. Wake characteristics of small-scale mesh disk rotor simulators have been measured in a 21
m tilting flume at the University of Southampton. The results indicate that wake velocities are reduced in the near wake region (close behind the rotor disk) for increasing levels of disk thrust. Further downstream all normalised wake velocity values converge, enforcing that, as for wind turbines, far wake recovery is a function of the ambient flow turbulence. Varying the disk proximity to the water surface/bed introduces differential mass flow rates above and below the rotor disk that can cause the wake to persist much further downstream. Finally, the introduction of increased sea bed roughness whilst increasing the depth-averaged ambient turbulence actually decreases downstream wake velocities. Results presented demonstrate that there are a number of interdependent variables that affect the rate of wake recovery and will have a significant impact on the spacing of marine current turbines within an array.
Introduction
Preeclampsia affects about 3% of singleton pregnancies and is characterized by placental dysfunction. It is associated with significant maternal and perinatal morbidity and mortality. ...The diagnosis of preeclampsia remains a challenge, and the clinical course can develop for weeks before a diagnosis is confirmed. National guidelines have approved placental growth factor (PlGF) testing to rule out suspected preeclampsia, but the utility of repeated PlGF measurement is unknown. The aim of this case series analysis was to evaluate the test performance of repeated PlGF sampling in women presenting with suspected preeclampsia, and to describe relevant clinical outcomes.
Material and methods
Women who presented to maternity services with suspected preeclampsia between 20+0 and 36+6 weeks’ gestation who underwent repeat PlGF sampling with a minimum test interval of 7 days were assessed. The outcomes were delivery for preeclampsia within 14 days of sampling, the proportion changing PlGF categories, and time to delivery.
Results
In total, 289 women with suspected preeclampsia undergoing repeat PlGF sampling were included. PlGF <100 pg/mL had a high sensitivity (87.5%, 95% confidence interval CI 67.6%‐97.3%) and a negative predictive value (97.7%, 95% CI 93.5%‐99.5%) at the initial test (receiver operating characteristic ROC area 0.79, 95% CI 0.68‐0.89). Similar test performance was seen for PlGF <100 pg/mL when undertaken as a repeat test (sensitivity 90.7%, 95% CI 85.2%‐95.9%, negative predictive value 92.2%, 95% CI 85.3‐96.6%). Overall, 25.6% of women changed PlGF category between the first and second PlGF tests. For each PlGF category, determination of time to delivery was similar for first and second tests.
Conclusions
Repeat PlGF measurement demonstrates high negative predictive value for determining preeclampsia requiring delivery in 14 days. Repeat testing may be clinically useful to risk stratify women with ongoing symptoms of disease. Confirmation of the impact of these findings is required in further studies.
Positive definiteness represents an admissibility condition for a function to be a covariance. Nevertheless, the more restricted condition of strict positive definiteness has received attention in ...literature, especially in spatial statistics, since it ensures that the kriging system has a unique solution. Most known covariance functions are isotropic but there are applications where isotropy is not appropriate, e.g., space-time covariance functions. One way to construct non-isotropic covariance functions is to use a product or a product-sum. In this article, it is given a necessary as well as a sufficient condition for a product of two covariance functions to be strictly positive definite. This result is extended to the well-known product-sum covariance model.
Current driver mortality estimates do not consider the great differences in exposure across the population, giving a false impression that driver deaths are lowest in the youngest age group. ...Interventions to reduce risk among the younger age group include graduated driver licensing (GDL) - a three-phase licensing system for novice drivers consisting of a learner's permit, a provisional license, and a full license.
We calculated driver fatality rates per 10 000 registered drivers in each age group and assessed the need for stricter licensing conditions for novice and younger drivers.
Age-specific driver mortality rates were calculated using Western Cape Province 2008 mortuary data. The total number of licensed drivers in each age group served as the denominator. Incidence rate ratios were calculated using the age group of 65 - 79 years as the reference. Chi-square test of trend on incidence rate ratios for the age groups was done. Statistical significance was set as p<0.05.
There were 339 driver deaths; mean age was 39.4±13.8 years, and males accounted for 80% of the deaths. Age-specific driver mortality rates were highest in the youngest age group (15 - 19 years). There was a significant progressive decrease (except for the age group 45 - 49 years) in the risk of death from road traffic injuries with increasing age compared with the age group ≥ 65 years (chi2 for trend p<0.0001). CONCLUSION; This study showed a relationship between driver's mortality risk and younger age, and underscores the need for introduction of a GDL programme in South Africa.
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