Learning neural codes for perceptual uncertainty

Perception is an inferential process, in which the state of the immediate environment must be estimated from sensory input. Inference in the face of noise and ambiguity requires reasoning with uncertainty, and much animal behaviour appears close to Bayes optimal. This observation has inspired hypotheses for how the activity of neurons in the brain might represent the distributional beliefs necessary to implement explicit Bayesian computation. While previous work has focused on the sufficiency of these hypothesised codes for computation, relatively little consideration has been given to optimality in the representation itself. Here, we adopt an encoder-decoder approach to study representational optimisation within one hypothesised belief encoding framework: the distributed distributional code (DDC). We consider a setting in which typical belief distribution functions take the form of a sparse combination of an underlying set of basis functions, and the corresponding DDC signals are corrupted by neural variability. We estimate the conditional entropy over beliefs induced by these DDC signals using an appropriate decoder. Like other hypothesised frameworks, a DDC representation of a belief depends on a set of fixed encoding functions that are usually set arbitrarily. Our approach allows us to seek the encoding functions that minimise the decoder conditional entropy and thus optimise representational accuracy in an information theoretic sense. We apply the approach to show how optimal encoding properties may adapt to represent beliefs in new environments, relating the results to experimentally reported neural responses

A second anniversary operational review of the OmniTRACS(R): The first two-way mobile Ku-band satellite communications system

A novel two-way mobile satellite communications and vehicle position reporting system that is currently operational in the United States and Europe is described. The system characteristics and service operations are described in detail. Technical descriptions of the equipment and signal processing techniques are provided

The role of circumstances in explaining health and income related inequalities in European countries

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Analysis of turbulence effects in a patient-specific aorta with aortic valve stenosis

Blood flow in the aorta is often assumed laminar, however aortic valve pathologies may induce transition to turbulence and our understanding of turbulence effects is incomplete. The aim of the study was to provide a detailed analysis of turbulence effects in aortic valve stenosis (AVS). Methods: Large-eddy simulation (LES) of flow through a patient-specific aorta with AVS was conducted. Magnetic resonance imaging (MRI) was performed and used for geometric reconstruction and patient-specific boundary conditions. Computed velocity field was compared with 4D flow MRI to check qualitative and quantitative consistency. The effect of turbulence was evaluated in terms of fluctuating kinetic energy, turbulence-related wall shear stress (WSS) and energy loss. Results: Our analysis suggested that turbulence was induced by a combination of a high velocity jet impinging on the arterial wall and a dilated ascending aorta which provided sufficient space for turbulence to develop. Turbulent WSS contributed to 40% of the total WSS in the ascending aorta and 38% in the entire aorta. Viscous and turbulent irreversible energy losses accounted for 3.9 and 2.7% of the total stroke work, respectively. Conclusions: This study demonstrates the importance of turbulence in assessing aortic haemodynamics in a patient with AVS. Neglecting the turbulent contribution to WSS could potentially result in a significant underestimation of the total WSS. Further work is warranted to extend the analysis to more AVS cases and patients with other aortic valve diseases

Infective endocarditis: do we have an effective risk score model? A systematic review

Background Infective endocarditis (IE) is a rare, highly morbid condition with 17% in-hospital mortality. 25-30% require surgery and there is ongoing debate with regard to markers predicting patient outcomes and guiding intervention. This systematic review aims to evaluate all IE risk scores currently available. Methods Standard methodology (PRISMA guideline) was used. Papers with risk score analysis for IE patients were included, with attention to studies reporting area under the receiver-operating characteristic curve(AUC/ROC). Qualitative analysis was carried out, including assessment of validation processes and comparison of these results to original derivation cohorts where available. Risk-of-bias analysis illustrated according to PROBAST guidelines. Results Of 75 articles initially identified, 32 papers were analysed for a total of 20 proposed scores, (range 66-13,000 patients), 14 of which were specific for IE. The number of variables per score ranged from 3 to 14 with only 50% including microbiological variables and 15% including biomarkers. The following scores had good performance (AUC>0.8) in studies proposing the score (often the derivation cohort); however fared poorly when applied to a new cohort: PALSUSE, DeFeo, ANCLA, RISK-E, EndoSCORE, MELD-XI, COSTA, SHARPEN. DeFeo score demonstrated the largest discrepancy with initial AUC of 0.88, compared to 0.58 when applied to different cohorts. The inflammatory response in IE has been well documented and CRP has been found to be an independent predictor for worse outcomes. There is ongoing investigation on alternate inflammatory biomarkers which may assist in IE management. Of the scores identified in this review, only 3 have included a biomarker as a predictor. Conclusion Despite the variety of available scores, their development has been limited by small sample size, retrospective collection of data and short-term outcomes, with lack of external validation, limiting their transportability. Future population studies and large comprehensive registries are required to address this unmet clinical need

BISMICS consensus statement: implementing a safe minimally invasive mitral programme in the UK healthcare setting

Disseminating the practice of minimally invasive mitral surgery (mini-MVS) can be challenging, despite its original case reports a few decades ago. The penetration of this technology into clinical practice has been limited to centres of excellence and mitral surgery in most general cardiothoracic centres remains to be conducted via sternotomy access as a first line. The process for the uptake of mini-MVS requires clearer guidance and standardisation for the processes involved in its implementation. In this statement, a consensus agreement is outlined that describes the benefits of mini-MVS, including reduced post-operative bleeding, reduced wound infection, enhanced recovery and patient satisfaction. Technical considerations require specific attention and can introduced through simulation and/or use in conventional cases. Either endoballoon or aortic cross clamping are both recommended as well as femoral or central aortic cannulation, with the use of appropriate adjuncts and instruments. A coordinated team-based approach that encourages ownership of the programme by the team members is critical. A designated proctor is also recommended. The organisation of structured training and simulation, as well as planning the initial cases are important steps to consider. The importance of pre-empting complications and dealing with adverse events are described, including re-exploration, conversion to sternotomy, uni-lateral pulmonary oedema and phrenic nerve injury. Accounting for both institutional and team considerations can effectively facilitate the introduction of a mini-MVS service. This involves simulation, team-based training, visits to specialist centres and involvement of a designated proctor to oversee the initial cases

Converging rapid deployment prostheses with minimal access surgery: analysis of early outcomes

Background: Sutureless prostheses may have added benefit when combined with minimal access surgery, although this has not been fully assessed in the literature. This study aims to provide a comparative analysis of the Perceval valve comparing median sternotomy (MS) with mini-sternotomy (MIS). Methods: A retrospective analysis of prospectively collected data was conducted for all isolated aortic valve replacement (AVR), using the Perceval valve, for severe aortic stenosis cases in the period 2014 to 2019. Patients undergoing concomitant valve or revascularisation surgery were excluded. Results: A total of 78 patients were included: MS group 41; MIS group 37. Operatively, bypass times were comparable between MS and MIS groups (mean 89.3 vs 83.4, p = 0.307), as were aortic cross clamp times (58.4 vs 55.9, p = 0.434). There were no operative deaths or new onset post-operative neurology. MIS was a predictor of reduced stay in the intensive care unit (coef − 3.25, 95% CI [− 4.93, − 0.59], p = 0.036) and hospital stay overall (p = 0.004). Blood transfusion units were comparable as were the incidence of heart block (n = 5 vs n = 3, p = 0.429) and new onset atrial fibrillation (n = 15 vs n = 9, p = 0.250). Follow-up echocardiography found a significant improvement in effective orifice area, left ventricular dimension and volume indices, and LVEF (p > 0.05) for all patients. Multivariate analysis found mini-sternotomy to be a predictor for reduced LV diastolic volume (coef − 0.35, 95% CI [− 1.02, − 0.05], p = 0.05). Conclusions: The combination of minimal access surgery and sutureless AVR may enhance patient recovery and provide early LV remodelling

Impact of immigration on burden of Tuberculosis in Umbria: a low-incidence Italian region with high immigrants rates

Introduction. In Italy, Tubercolosis (TB) has increasingly become a disease for specific population subgroups such as immi- grants. The objective of this paper is to describe the trend in TB incidence from 1999 to 2008 in Umbria: a low-incidence Italian region with high immigrants rates. Methods. Data were obtained from the Regional Information System for Infectious Diseases. Using a linear regressions model we estimated trends for number of cases and incidence rates; with a logistic regression model we estimated the effect of a set of covariates on the probability of being affected by TB. Result. 590 TB cases were reported of whom 254 (43%) were foreign. In 2008 39.7 new cases per 100.000 were registered among foreign-born subjects. TB incidence among Italians was 3.8/100.000 Italians. But a linear regression analysis showed a statistically significant decreasing trend in the notification rate among foreign-born people (coef: -7.32, r2:0.57, p inf. 0.05). The probability to be affected by extra-pulmonary is significantly larger in foreign patients (OR = 0.72, CI = 0.48-1.07). Foreign unskilled workers report a higher probability to be affected by TB (OR = 19.05, CI = 6.01-60.4). Discussion. Increasing immigration rates may affect TB epide- miology. The analysis of incidence trends is an important tool for monitoring tuberculosis disease control and to identify specific sub-group at risk