The effect of neural adaptation of population coding accuracy

Most neurons in the primary visual cortex initially respond vigorously when a preferred stimulus is presented, but adapt as stimulation continues. The functional consequences of adaptation are unclear. Typically a reduction of firing rate would reduce single neuron accuracy as less spikes are available for decoding, but it has been suggested that on the population level, adaptation increases coding accuracy. This question requires careful analysis as adaptation not only changes the firing rates of neurons, but also the neural variability and correlations between neurons, which affect coding accuracy as well. We calculate the coding accuracy using a computational model that implements two forms of adaptation: spike frequency adaptation and synaptic adaptation in the form of short-term synaptic plasticity. We find that the net effect of adaptation is subtle and heterogeneous. Depending on adaptation mechanism and test stimulus, adaptation can either increase or decrease coding accuracy. We discuss the neurophysiological and psychophysical implications of the findings and relate it to published experimental data.Comment: 35 pages, 8 figure

Slim cables, compact cross-bonding and corrected distance protection

In the Netherlands, high voltage connections will increasingly be realized using cables as it is very difficult to get permits for overhead lines. Pirelli and Nuon are continuously improving the design and production of the cables for increased reliability and capacity as well as lower costs. To this end, the present XLPE insulated cable has been optimized using a thinner primary insulation and lead sheath. The layout of production has been improved to lower manufacturing costs. Cable capacity has been improved by the choice for a thinner lead screen as well as increased use of cross-bonding. A cross-bonding box has been developed that allows capacity to be increased significantly at limited additional costs. The distance protection of cables has been revised to correct the calculation error caused by the return current in the screen. It is shown that adequate correction can be achieved using a real value which depends only on cable characteristics. This considerably eases implementation into new and in existing systems

Quantifying health effects of nutrition

Modelsimulaties geven aan dat met een grotere consumptie van fruit, groente en vis veel gezondheidswinst te behalen is. Dit soort schattingen kunnen worden gebruikt bij de onderbouwing van het voedingsbeleid. Met behulp van het Chronische-Ziekten-Model (CZM) van het RIVM kunnen de gezondheidseffecten op de langere termijn en zorggerelateerde kosten van beleidsdoelstellingen en voedingsinterventies worden doorgerekend. De modelsimulaties geven aan dat met een verhoging van de consumptie van groenten, fruit en vis relatief veel gezondheidswinst te behalen is. Ook blijkt dat ten aanzien van de vetzuursamenstelling de meeste gezondheidswinst inmiddels al is bereikt. Als de gehele Nederlandse bevolking de aanbevelingen voor gezonde voeding zou naleven, overlijden de komende twintig jaar naar schatting 140.000 minder mensen. De totale zorgkosten die anders in 20 jaar worden uitgegeven verminderen dan ongeveer met 3%. Doordat mensen langer leven zullen in de daaropvolgende jaren hun zorgkosten wel toenemen. Het model is ook gebruikt voor doorrekening van twee concrete voedingsinterventies, te weten SchoolGruiten en Werkfruit. Een kind dat deelneemt aan SchoolGruiten zal gemiddeld langer leven (+0,37 jaar) en ook langer gezond blijven. Er worden minder medische kosten op jongere leeftijd gemaakt. Deze kosten worden echter voor een groot deel uitgesteld. Voorwaarde voor de gunstige effecten is dat kinderen na de basisschool structureel meer groenten en fruit blijven eten. Werkfruit is een interventie die zich richt op de fruitconsumptie van werknemers in Nederland. Wanneer dit wordt ingevoerd bij 1 op de 10 werknemers, stijgt naar verwachting de levensverwachting van een 20-jarige met 0,08 jaar en nemen de gezondheidszorgkosten met 0,2 procent af.Simulations show that with an elevation of fruit, vegetable and fish consumption large health gains can be achieved. Model simulation is a good method to underpin nutritional policy. The RIVM Chronic Disease Model (CZM) can be used to calculate long term health effects and health care related costs of policy targets and dietary interventions. Simulations show that with an elevation of fruit, vegetable and fish consumption large health gains can be achieved. On the other hand, most health benefits related to fatty acids composition are already achieved. If the Dutch population complies with the dietary recommendations on nutrition, in 20 years, about 140,000 deaths and about 3% of the costs of health care will be saved. As the life expectancy increases people will experience health costs later in life. Two dietary interventions, 'SchoolGruiten' and 'Werkfruit' are simulated within CZM. Children participating in 'SchoolGruiten' will see their life expectancy increased (+0.37 year). They will also, on average, stay healthy for a longer time, assuming long term effects of the intervention. In this way such a child will make less medical costs at a younger age, however most of this costs are only postponed. Introducing 'Werkfruit' in the Netherlands onto one out of 10 employers, will increase the life expectancy of an 20-year old by an estimated 0.08 year and decrease the health-related costs of the whole population with 0.2 percent

Event-driven simulations of a plastic, spiking neural network

We consider a fully-connected network of leaky integrate-and-fire neurons with spike-timing-dependent plasticity. The plasticity is controlled by a parameter representing the expected weight of a synapse between neurons that are firing randomly with the same mean frequency. For low values of the plasticity parameter, the activities of the system are dominated by noise, while large values of the plasticity parameter lead to self-sustaining activity in the network. We perform event-driven simulations on finite-size networks with up to 128 neurons to find the stationary synaptic weight conformations for different values of the plasticity parameter. In both the low and high activity regimes, the synaptic weights are narrowly distributed around the plasticity parameter value consistent with the predictions of mean-field theory. However, the distribution broadens in the transition region between the two regimes, representing emergent network structures. Using a pseudophysical approach for visualization, we show that the emergent structures are of "path" or "hub" type, observed at different values of the plasticity parameter in the transition region.Comment: 9 pages, 6 figure

Collimation and asymmetry of the hot blast wave from the recurrent nova V745 Scorpii

The recurrent symbiotic nova V745 Sco exploded on 2014 February 6 and was observed on February 22 and 23 by the Chandra X-ray Observatory Transmission Grating Spectrometers. By that time the supersoft source phase had already ended and Chandra spectra are consistent with emission from a hot, shock-heated circumstellar medium with temperatures exceeding 10^7K. X-ray line profiles are more sharply peaked than expected for a spherically-symmetric blast wave, with a full width at zero intensity of approximately 2400 km/s, a full width at half maximum of 1200 +/- 30 km/s and an average net blueshift of 165 +/- 10 km/s. The red wings of lines are increasingly absorbed toward longer wavelengths by material within the remnant. We conclude that the blast wave was sculpted by an aspherical circumstellar medium in which an equatorial density enhancement plays a role, as in earlier symbiotic nova explosions. Expansion of the dominant X-ray emitting material is aligned close to the plane of the sky and most consistent with an orbit seen close to face-on. Comparison of an analytical blast wave model with the X-ray spectra, Swift observations and near-infrared line widths indicates the explosion energy was approximately 10^43 erg, and confirms an ejected mass of approximately 10^-7 Msun. The total mass lost is an order of magnitude lower than the accreted mass required to have initiated the explosion, indicating the white dwarf is gaining mass and is a supernova Type 1a progenitor candidate.Comment: To appear in the Astrophysical Journa

Increasing feasibility and patient comfort of MRI in children with juvenile idiopathic arthritis

MRI is the most sensitive imaging modality in juvenile idiopathic arthritis (JIA), but has practical limitations. Optimizing the scanning protocol is, therefore, necessary to increase feasibility and patient comfort. To determine the feasibility of bilateral non-contrast-enhanced open-bore MRI of knees and to assess the presence of literature-based MRI features in unsedated children with JIA. Children were classified into two clinical subgroups: active arthritis (group 1; n = 29) and inactive disease (group 2; n = 18). MRI features were evaluated using a literature-based score, comprising synovial hypertrophy, cartilage lesions, bone erosions, bone marrow changes, infrapatellar fat pad heterogeneity, effusion, tendinopathy and popliteal lymphadenopathy. The MRI examination was successfully completed in all 47 children. No scan was excluded due to poor image quality. Synovial hypertrophy was more frequent in group 1 (36.2%), but was also seen in 19.4% of the knees in group 2. Infrapatellar fat pad heterogeneity was more prevalent in group 2 (86.1%; P = 0.008). Reproducibility of the score was good (Cohen kappa, 0.49-0.96). Bilateral non-contrast-enhanced open-bore knee MRI is feasible in the assessment of disease activity in unsedated children with JIA. Signs differing among chidren with active and inactive disease include infrapatellar fat pad heterogeneity and synovial hypertroph

Trans-generational stress regulation: Mother-infant cortisol and maternal mental health across the perinatal period

Understanding maternal mental health and cortisol regulation across pregnancy and the relationship to the development of the offspring’s stress regulation is critical to a range of health outcomes. The aim of this study was to investigate infant and maternal cortisol in women with depression. Data were obtained from 241 pregnant women within the Mercy Pregnancy and Emotional Wellbeing Study (MPEWS), a selected pregnancy cohort study. Depression was measured using the Structured Clinical Interview for DSM-IV (SCID-IV) and repeat Edinburgh Postnatal Depression Scale (EPDS). Repeated measures of antidepressant use, stressful events, anxiety symptoms and maternal hair cortisol concentrations (HCC) and infant cortisol at 12 months postpartum in saliva and hair. Socio-emotional outcomes were measured at 12 months by maternal report on the Brief Infant and Toddler Socio-emotional Assessment (BITSEA). This study found that maternal depression was not associated with maternal HCC. Anxiety, stress and antidepressant use were not associated with maternal HCC. Independently, higher maternal 3rd trimester maternal depressive and anxiety symptoms were associated with lower infant cortisol response at 12 months of age. A higher number of postpartum stressful events was associated with lower infant cortisol response. Lower infant stress reactivity was associated with higher externalizing symptoms at 12 months of age. Future studies are required to understand implications for later mental health