Space, time and memory in the medial temporal lobe

This thesis focuses on memory and the representation of space in the medial temporal lobe, their interaction and their temporal structure. Chapter 1 briefly introduces the topic, with emphasis on the open questions that the subsequent chapters aim to address. Chapter 2 is dedicated to the issue of spatial memory in the medial entorhinal cortex. It investigates the possibility to store multiple independent maps in a recurrent network of grid cells, from a theoretical perspective. This work was conducted in collaboration with Remi Monasson, Alexis Dubreuil and Sophie Rosay and is published in (Spalla et al. 2019). Chapter 3 focuses on the problem of the dynamical update of the representation of space during navigation. It presents the results of the analysis of electrophysiological data, previously collected by Charlotte Boccara (Boccara et al., 2010), investigating the encoding of self-movement signals (speed and angular velocity of the head) in the parahippocampal region of rats. Chapter 4 addresses the problem of the temporal dynamics of memory retrieval, again from a computational point of view. A continuous attractor network model is presented, endowed with a mechanism that makes it able to retrieve continuous temporal sequences. The dynamical behaviour of the system is investigated with analytical calculations and numerical simulations, and the storage capacity for dynamical memories is computed. Finally, chapter 4 discusses the meaning and the scope of the results presented, and highlights possible future directions

Angular and Linear Speed Cells in the Parahippocampal Circuits

An essential role of the hippocampal region is to integrate information to compute and update representations. How this transpires is highly debated. Many theories hinge on the integration of self-motion signals and the existence of continuous attractor networks (CAN). CAN models hypothesise that neurons coding for navigational correlates – such as position and direction – receive inputs from cells conjunctively coding for position, direction and self-motion. As yet, such conjunctive coding had not been found in the hippocampal region. Here, we report neurons coding for angular and linear velocity, distributed across the medial entorhinal cortex, the presubiculum and the parasubiculum. These self-motion neurons often conjunctively encoded position and/or direction, yet lacked a structured organisation, calling for the revision of current CAN models. These results offer insights as to how linear/angular speed – derivative in time of position/direction – may allow the updating of spatial representations, possibly uncovering a generalised algorithm to update any representation

Report of an interlaboratory comparison organised by the EU Reference Laboratory for Food Contact Materials - ILC01 2009 - DIDP in Oil Laboratory performance and precision criteria of a harmonised method

The Institute for Health and Consumer Protection (IHCP) of the European Commission¿s Directorate-General Joint Research Centre hosts the European Union Reference Laboratory for Food Contact Materials (EURL-FCM). One of its core tasks is to organize interlaboratory comparisons (ILCs) among appointed National Reference Laboratories (NRLs). This report presents the results of the second ILC of the EURL-FCM which focused on the determination of Di-isodecyl phthalate (DIDP) in an oil matrix. The aim was to develop and perform the validation of a method for the analysis of DIDP (as model substance for a technical mixture of phthalates) from oil (as simulant for fatty foods). This exercise was used both as proficiency testing and to validate a standard operating procedure (SOP) for the determination of DIDP in oil that was written by the EURL based on the most performant methods used by NRLs in the proficiency test of 2008. Participation of local laboratories under NRLs was encouraged (by producing 60 samples). There were 28 participants to whom samples were dispatched 24 of which submitted results. From the EURL-NRL network 23 laboratories out of 24 reported results. There were 2 guests from Germany that provided results as well. Participants were invited to report four replicates measurements under repeatability conditions. The ILC was closed permanently in the middle of October for statistical interpretation. Based on the results in this precision experiment the method performance was assessed through evaluation of the repeatability and reproducibility standard deviation (SD) according to the mechanism described in ISO 5725 [11,12]. The assigned value and its uncertainty were obtained as a consensus values after applying the robust statistics to the results obtained from the participants. Laboratory results were rated with z and z¿ scores in accordance with ISO 13528 [1]. Standard deviations for proficiency assessment (also called target standard deviations) were set based on Horwitz equation. The participation of the laboratories was regarded as satisfactory for the aim of the precision experiment with regards of the numbers of received results thanks to the proactive involvement of the NRLs-FCM. As a conclusion for participation and laboratory performance, this ILC showed: A noted increase in participation compared to the similar exercise of 2008. The number of laboratories submitting results for DIDP in oil rose from 17 to 25. This was due in part from the experience acquired in the previous year exercise as well as to the provision by the EURL of both the method description in a CEN like format as well as of the internal standard. A great increase in laboratory performance compared to 2008 with 76-92% of successful achievement of results from the participants within the tolerance limits (range 76-92% depended on concentration level considered) compared to 59% in 2008. In particular the performance at the concentration level of the SML was 80% compared to 59% for the same exercise in 2008. The harmonisation of the procedure and following a harmonised method for determination of DIDP in oil in 2009 resulted in a decrease more then 2.5 times in the reproducibility SD from 37% to 14 % for the concentration level around SML of 9 mg/kg while the repeatability SD remained almost the same ¿ 6.5%.JRC.DG.I.2-Chemical assessment and testin

Improving sensitivity of a small angle x-ray scattering camera with pinhole collimation using separated optical elements

International audienceWe show that a significant improvement in the sensitivity of a Huxley–Holmes design for a small angle x-ray scattering camera is obtained by separating the mirror and the monochromator. The design of the camera involves a long x-ray mirror close to a point x-ray source associated with a curved focusing crystal located close to the sample. The sample area is located at half the distance between the source and detector planes. Diffuse scattering produced by the mirror is not incident on the focusing crystal, thus reducing the background signal. Complete elimination of hard x rays allows precise calibration and hence absolute determination of sample cross section by means of a semitransparent beam stop. In pinhole geometry, the flux corresponds to a ;107 photons/s through the sample, collimated to 1022 Å21 in q range. This allows determination of scattered intensities on the order of 1023 cm21, corresponding to the scattering related to isothermal compressibility of less than 0.1 mm of pure water. As a reference sample, the widely used Lupolen™, a semicrystalline polymer, is calibrated. The high-q limit (q'4.5 nm21) of a porous calcite sample can be used as a secondary standard for specific area determination of solid/solid or solid–liquid dispersions

Continuous attractors for dynamic memories

Episodic memory has a dynamic nature: when we recall past episodes, we retrieve not only their content, but also their temporal structure. The phenomenon of replay, in the hippocampus of mammals, offers a remarkable example of this temporal dynamics. However, most quantitative models of memory treat memories as static configurations, neglecting the temporal unfolding of the retrieval process. Here, we introduce a continuous attractor network model with a memory-dependent asymmetric component in the synaptic connectivity, which spontaneously breaks the equilibrium of the memory configurations and produces dynamic retrieval. The detailed analysis of the model with analytical calculations and numerical simulations shows that it can robustly retrieve multiple dynamical memories, and that this feature is largely independent of the details of its implementation. By calculating the storage capacity, we show that the dynamic component does not impair memory capacity, and can even enhance it in certain regimes

Medication reconciliation as a strategy for preventing medication errors

Uma das barreiras propostas para se evitar possíveis erros relacionados a medicamentos e, consequentemente, que danos acometam o paciente, é a reconciliação medicamentosa no ato da internação, processo no qual se comparam os medicamentos usados pelos pacientes previamente à internação com os prescritos no âmbito hospitalar. Este trabalho descreve os resultados de seis meses de um processo de reconciliação conduzido por farmacêutico em unidades clínicas de um hospital universitário. Quatorze pacientes (23.33%) tiveram algum tipo de problema relacionado ao uso de medicamentos. A maioria dos erros envolvendo medicamentos (80%) estava relacionada à omissão de medicamentos. As intervenções farmacêuticas tiveram 90% de aceitação pelos médicos. Os resultados sugerem que a atuação de farmacêuticos na reconciliação medicamentosa pode desempenhar papel relevante na prevenção de erros de medicamentos e eventos adversos. Além disso, a entrevista detalhada conduzida por um farmacêutico se mostrou capaz de resgatar informações importantes sobre o uso dos medicamentos, permitindo evitar erros e danos ao paciente.One of the current barriers proposed to avoid possible medication errors, and consequently harm to patients, is the medication reconciliation, a process in which drugs used by patients prior to hospitalization can be compared with those prescribed in the hospital. This study describes the results of a pharmacist based reconciliation conducted during six months in clinical units of a university hospital. Fourteen patients (23.33%) had some kind of problem related to medicine. The majority (80%) of medication errors were due to medication omission. Pharmaceutical interventions acceptance level was 90%. The results suggest that pharmacists based reconciliation can have a relevant role in preventing medication errors and adverse events. Moreover, the detailed interview, conducted by the pharmacist, is able to rescue important information regarding the use of drugs, allowing to avoid medications errors and patient injury

A general method for the synthesis of nanostructured large-surface-area materials through the self-assembly of functionalized nanoparticles

A general synthetic method for the preparation of nanostructured materials with large surface area was developed by using nanoparticle building blocks. The preparation route involves the self-assembly of functionalized nanoparticles in a liquid-crystal phase. These nanoparticles are functionalized by using difunctional amino acid species to provide suitable interactions with the template. Optimum interactions for self-assembly of the nanoparticles in the liquid-crystal phase were achieved with one -NH2 group anchored to the nanoparticle surface per 25 Å2. To maximize the surface area of these materials, the wall thicknesses are adjusted so that they are composed of a monolayer of nanoparticles. To form such materials, numerous parameters have to be controlled such as the relative volume fraction of the nanoparticles and the template and size matching between the hydrophilic component of the copolymer and nanoparticles. The surface functionalization renders our synthetic route independent of the nanoparticles and allows us to prepare a variety of nanostructured composite materials that consist of a juxtaposition of different discrete oxide nanoparticles. Examples of such materials include CeO2, ZrO2, and CeO2–Al(OH)3 composites