Imbalanced decision hierarchy in addicts emerging from drug-hijacked dopamine spiraling circuit

Despite explicitly wanting to quit, long-term addicts find themselves powerless to resist drugs, despite knowing that drug-taking may be a harmful course of action. Such inconsistency between the explicit knowledge of negative consequences and the compulsive behavioral patterns represents a cognitive/behavioral conflict that is a central characteristic of addiction. Neurobiologically, differential cue-induced activity in distinct striatal subregions, as well as the dopamine connectivity spiraling from ventral striatal regions to the dorsal regions, play critical roles in compulsive drug seeking. However, the functional mechanism that integrates these neuropharmacological observations with the above-mentioned cognitive/behavioral conflict is unknown. Here we provide a formal computational explanation for the drug-induced cognitive inconsistency that is apparent in the addicts' “self-described mistake”. We show that addictive drugs gradually produce a motivational bias toward drug-seeking at low-level habitual decision processes, despite the low abstract cognitive valuation of this behavior. This pathology emerges within the hierarchical reinforcement learning framework when chronic exposure to the drug pharmacologically produces pathologicaly persistent phasic dopamine signals. Thereby the drug hijacks the dopaminergic spirals that cascade the reinforcement signals down the ventro-dorsal cortico-striatal hierarchy. Neurobiologically, our theory accounts for rapid development of drug cue-elicited dopamine efflux in the ventral striatum and a delayed response in the dorsal striatum. Our theory also shows how this response pattern depends critically on the dopamine spiraling circuitry. Behaviorally, our framework explains gradual insensitivity of drug-seeking to drug-associated punishments, the blocking phenomenon for drug outcomes, and the persistent preference for drugs over natural rewards by addicts. The model suggests testable predictions and beyond that, sets the stage for a view of addiction as a pathology of hierarchical decision-making processes. This view is complementary to the traditional interpretation of addiction as interaction between habitual and goal-directed decision systems

The effects of the neurotoxin DSP4 on spatial learning and memory in Wistar rats

The aim of the present study was to investigate the effect of DSP4-induced noradrenaline depletion on learning and memory in a spatial memory paradigm (holeboard). Since Harro et al. Brain Res 976:209–216 (2003) have demonstrated that short-term effects of DSP4 administration include both noradrenaline depletion and changes in dopamine and its metabolites—with the latter vanishing within 4 weeks after the neurotoxic lesion—the behavioural effects observed immediately after DSP4 administration cannot solely be related to noradrenaline. In the present study, spatial learning, reference memory and working memory were therefore assessed 5–10 weeks after DSP4 administration. Our results suggest that the administration of DSP4 did not lead to changes in spatial learning and memory when behavioural assessment was performed after a minimum of 5 weeks following DSP4. This lack of changes in spatial behaviour suggests that the role of noradrenaline regarding these functions may be limited. Future studies will therefore have to take into account the time-course of neurotransmitter alterations and behavioural changes following DSP4 administration

Diffusion of Pure CH4 and Its Binary Mixture with CO2 in Faujasite NaY: A Combination of Neutron Scattering Experiments and Molecular Dynamics Simulations

The self-diffusion properties of pure CH4 and its binary mixture with CO2 within MY zeolite have been investigated by combining an experimental quasi-elastic neutron scattering (QENS) technique and classical Molecular dynamics simulations. The QENS measurements carried out at 200 K led to an unexpected self-diffusivity profile for Pure CH4 with the presence of a maximum for a loading of 32 CH4/unit cell, which was never observed before for the diffusion of apolar species in azeolite system With large windows. Molecular dynamics simulations were performed using two distinct microscopic models for representing the CH4/NaY interactions. Depending on the model, we are able to fairly reproduce either the magnitude or the profile of the self-diffusivity.Further analysis allowed LIS to provide some molecular insight into the diffusion mechanism in play. The QENS measurements report only a slight decrease of the self-diffusivity of CH4 in the presence of CO2 when the CO2 loading increases. Molecular dynamics simulations successfully capture this experimental trend and suggest a plausible microscopic diffusion mechanism in the case of this binary mixture

Silicon distribution in SAPO materials: A computational study of STA-7 combined to Si-29 MAS NMR spectroscopy

The distribution of silicon atoms in the STA-7 framework has been investigated by combining Si-29 MAS NMR spectroscopy and computational tools based on energy minimization techniques. It was clearly established that only a SM2 silicon substitution mechanism occurs for an atomic silicon content of 0.05 and 0.10, generating preferential sites for silicon atoms in the large channels associated with protons pointing systematically towards the centre of the cavities interacting with a 6-membered ring. The modelling techniques are used to propose the most stable configurations for the STA-7 frameworks of varying silicon content. This procedure allows us to provide a realistic microscopic description of the STA-7 material, a key step before further investigation of the properties of this system. (C) 2007 Elsevier Inc. All rights reserved.</p

Adsorption of volatile organic compounds in pure silica CHA, ⁄BEA, MFI and STT-type zeolites

International audienceFour pure silica zeolites, chabazite (CHA-structure type) and SSZ-23 (STT-structure type) with cage-like structure and silicalite-1 (MFI-structure type) and beta (⁄BEA-structure type) with channel structure, were synthesized and fully characterized. Their sorption properties were examined using gravimetric method combined with Grand Canonical Monte Carlo simulations (GCMC). Of particular interest is the large difference in the adsorption rates of n-hexane, p-xylene and acetone observed for these zeosils at 25, 75 and 150 C. As expected, in most cases, a decrease in the adsorption capacity is observed with increasing the molar volume of the used probe molecule and the temperature. An exception is observed for the pure silica CHA-type zeolite due to its small pore size which prevents molecules from entering its porosity. However, at higher temperature, the window size widens slightly and allows n-hexane and acetone, which have kinetic diameter close to the pore opening, to enter easily in chabazite. As a result, for this zeosil, an increase in the adsorption capacity compared to that obtained at 25 C is observed. All these zeosils are promising for technological uses in car exhaust gas decontamination

Exploring information technology (IT) sophistication in New South Wales residential aged care facilities

The aim of this study was to determine baseline information technology (IT) sophistication in New South Wales (NSW), Australia, residential aged care facilities. Method: IT sophistication measures IT capabilities, extent of IT use and IT integration in two domains, resident care and clinical support. A survey was administered to all NSW residential aged care facilities (n = 876) between February and May 2017. A 15% response rate was achieved (130/876). Facilities were organised by organisational type, total residential places and remoteness. Using post-stratification weights, estimates of IT sophistication scores for NSW were determined. Regression was used to examine whether there was a linear relationship between IT sophistication and the ratio of residents receiving high care. Results: Participating facilities were similar to other NSW facilities in residential places and remoteness, but different in organisational type. IT sophistication was highest in IT capabilities and integration in resident care. IT sophistication was lowest in clinical support. Respondents had a mean of 1.2 years of IT experience. IT sophistication varied among aged care facilities. There was a linear relationship (P < 0.05) with the proportion of high-care residents and total IT sophistication Conclusion: Routine reports of IT sophistication in aged care are not available. If data were available, determining the influence of IT sophistication on the quality care for residential aged care would be possible. What is known about the topic?: Aged care settings that deliver care to the older population need to be contemporary in their approach to delivering high-quality and safe care. Health IT holds great potential for improving the quality and safety of care of older residents in aged care facilities. What does this paper add?: This report provides a baseline assessment of IT capabilities, extent of IT use and IT integration, called IT sophistication, among aged care facilities with variable characteristics. What are implications for practitioners?: Increasing IT sophistication has the potential to improve the quality of care delivered by aged care staff

Evaluation of STA-7 and AlPO18 for the adsorption of CH4 and CO2: microcalorimetry, neutron scattering and molecular simulation

internationa

Hydrocarbon adsorption in the isostructural metal organic frameworks MIL-53(Cr) and MIL-47(V)

International audienc