In any given environment, an ensemble of principal excitatory cells in the hippocampus, called place cells, will be active at a specific, usually single, location. Together, these neurons participate in the formation of a mental representation of that environment, allowing flexible spatial navigation. For a long time, hippocampal principal cells were thought to form a relatively homogeneous population and the ability of any given cell to be active in a new environment was thought to be evenly distributed. Recent data, however, suggest a more complicated scheme. Evidence shows that, while a majority of cells are active in only one or few environments (‘plastic cells’) a small minority of neurons is active in most of them (‘rigid cells’). However, it remains unknown how rigid and plastic circuits map onto specific cellular/circuit properties, developmental origins and intrinsic/synaptic cellular plasticity, already described in the hippocampus. In order to address this specific question, this proposal is organized along 3 objectives. Objective#1 is to determine whether plastic and rigid circuits are anatomically segregated by their developmental origin and analyze their stability across time and varying contexts using in vivo calcium imaging. Objective #2 is to understand which cellular/circuit properties critically determine whether a neuron is functionally plastic or rigid. We will examine the intrinsic morpho-physiological properties, synapto-dendritic physiology and plasticity of rigid vs. plastic cells in vivo as well as in vitro. Lastly, objective #3 is to understand the computational benefits for navigational strategies of mixing rigid and plastic neurons into the same network. We will provide a predictive model that combines all the experimental datasets from the two previous objectives. By bringing together leading experts in a wide array of disciplines, ranging from developmental neurobiology, cellular physiology, systems and computational neuroscience, this project will highly contribute to the expected impacts set out in the program of the HBP flagship. It will provide high yield quantitative data, bridging the gap between cellular and circuit analysis of hippocampal function, that will certainly fuel simulations of the hippocampal network, in the framework of the proposal (WP3). It should also benefit society because the ability to flexibly navigate in an environment is vital for human’s autonomy and severely disrupted during aging and in various diseases such as Alzheimer’s disease and temporal lobe epilepsy. The project will test a new hypothesis concerning the functional organization of the cells responsible for spatial navigation and episodic memory formation. Identifying the “rigid” cell type and understanding its precise functional role within and across networks may therefore allow us to design new therapeutic procedures to restore network, cognitive and behavioral functions in pathological situations.

Marine Protected Areas (MPAs) will play a crucial role in the successful implementation of the European Biodiversity Strategy and the European Green Deal. They are locations where we can concentrate efforts to restore biodiversity and support the diversification of the blue economy to boost the sustainable use of marine resources. We have paid a lot of attention to the best ways to design and establish MPAs; yet with more than 17,000 MPAs now designated globally, less than a quarter have a clear management plan. Managing complex socioecological systems (SES) is harder and navigating them towards sustainability is even harder. That is particularly the case for MPAs for which biodiversity targets and the exploitation of regional ecosystem services have to be balanced. This project aims to find practical solutions to guide MPA managers in the best approaches to yield positive biodiversity outcomes while maintaining the ability of neighbouring communities to benefit from marine ecosystem services sustainably. Managers of MPAs in Madeira, France, Denmark and Sweden will together with scientists co-create the insights needed to develop this guide, based on a global synthesis of MPA data and detailed functional analyses at three case study sites. We will use data science and statistical modelling to determine the structure of interactions between biodiversity and the provision of ecosystem services (ES) in all current MPAs depending on their SES characteristics. We will then extend recent advances in theoretical ecological modelling to these socio-ecological networked systems to understand how management actions can tip MPA SES towards favorable states using three MPA case studies to benchmark models. With this insight, we will determine the characteristics that will yield desirable SES states. Monitoring is crucial to guide adaptive management plans along this MPA restoration journey. We will determine whether readily available biodiversity and ES indicators can be integrated with rapid sampling to develop a standardized ‘citizen monitoring’ approach that can provide the necessary and sufficient level of information needed to manage the transformative change at MPAs. Finally, we will tackle the policy interaction hurdles managers face when developing plans in regions where multiple MPAs have been designated with varied policy targets. We will determine how best to manage these MPA networks to add value for regional biodiversity and ES targets. This project will produce a decision support system for MPA managers, which we will make available in a user-friendly format complementing current international MPA guidelines to help increase the uptake of management plans for existing MPA networks. In addition, it will produce tangible advice on integrative governance for our practitioners that will meet current urgent needs for the three case study regions.