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"Grid cells"

Radek Gebauer, Jan Divíšek, Miloš Buřič, Martin Večeřa, Antonín Kouba, Bořek Drozd
Biogeographical barriers formed by natural forces over billions of years have been substantially disrupted by human activity, particularly in recent centuries. In response to these anthropogenic changes, global homogenization of biota is observed at an ever-increasing rate, causing environmental and economic losses as well as emerging health risks. Identifying factors underlying alien species richness is essential for prevention of future introductions and subsequent spread. In this study, we examined the effects of environmental and human-related factors on distribution of alien animal species richness in the Czech Republic (Central Europe)...
May 2018: Ecology and Evolution
Zhiwei Wang, Xin Yang, Kwang-Ting Cheng
Non-contact heart rate (HR) measurement from facial videos has attracted high interests due to its convenience and cost effectiveness. However, accurate and robust HR estimation under various realistic scenarios remain a very challenging problem. In this paper, we develop a novel system which can achieve a robust and accurate HR estimation under those challenging scenarios. First, to minimize tracking-artifacts arising from large head motions and facial expressions, we propose a joint face detection and alignment method which can produce alignment-friendly facial bounding boxes with reliable initial facial shapes, facilitating accurate and robust face alignment even in the presence of large pose variations and expressions...
2018: PloS One
Andrea Banino, Caswell Barry, Benigno Uria, Charles Blundell, Timothy Lillicrap, Piotr Mirowski, Alexander Pritzel, Martin J Chadwick, Thomas Degris, Joseph Modayil, Greg Wayne, Hubert Soyer, Fabio Viola, Brian Zhang, Ross Goroshin, Neil Rabinowitz, Razvan Pascanu, Charlie Beattie, Stig Petersen, Amir Sadik, Stephen Gaffney, Helen King, Koray Kavukcuoglu, Demis Hassabis, Raia Hadsell, Dharshan Kumaran
Deep neural networks have achieved impressive successes in fields ranging from object recognition to complex games such as Go1,2 . Navigation, however, remains a substantial challenge for artificial agents, with deep neural networks trained by reinforcement learning3-5 failing to rival the proficiency of mammalian spatial behaviour, which is underpinned by grid cells in the entorhinal cortex 6 . Grid cells are thought to provide a multi-scale periodic representation that functions as a metric for coding space7,8 and is critical for integrating self-motion (path integration)6,7,9 and planning direct trajectories to goals (vector-based navigation)7,10,11 ...
May 9, 2018: Nature
Robert F Chew, Safaa Amer, Kasey Jones, Jennifer Unangst, James Cajka, Justine Allpress, Mark Bruhn
BACKGROUND: Conducting surveys in low- and middle-income countries is often challenging because many areas lack a complete sampling frame, have outdated census information, or have limited data available for designing and selecting a representative sample. Geosampling is a probability-based, gridded population sampling method that addresses some of these issues by using geographic information system (GIS) tools to create logistically manageable area units for sampling. GIS grid cells are overlaid to partition a country's existing administrative boundaries into area units that vary in size from 50 m × 50 m to 150 m × 150 m...
May 9, 2018: International Journal of Health Geographics
Nándor Fodor, Andreas Foskolos, Cairistiona F E Topp, Jon M Moorby, László Pásztor, Christine H Foyer
Dairy farming is one the most important sectors of United Kingdom (UK) agriculture. It faces major challenges due to climate change, which will have direct impacts on dairy cows as a result of heat stress. In the absence of adaptations, this could potentially lead to considerable milk loss. Using an 11-member climate projection ensemble, as well as an ensemble of 18 milk loss estimation methods, temporal changes in milk production of UK dairy cows were estimated for the 21st century at a 25 km resolution in a spatially-explicit way...
2018: PloS One
Xueying Zhang, Yiyi Chu, Yuxuan Wang, Kai Zhang
BACKGROUND AND OBJECTIVE: The regulatory monitoring data of particulate matter with an aerodynamic diameter <2.5μm (PM2.5 ) in Texas have limited spatial and temporal coverage. The purpose of this study is to estimate the ground-level PM2.5 concentrations on a daily basis using satellite-retrieved Aerosol Optical Depth (AOD) in the state of Texas. METHODS: We obtained the AOD values at 1-km resolution generated through the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm based on the images retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellites...
August 1, 2018: Science of the Total Environment
Christopher M Clark, Jennifer Phelan, Prakash Doraiswamy, John Buckley, James C Cajka, Robin L Dennis, Jason Lynch, Christopher G Nolte, Tanya L Spero
Atmospheric deposition of nitrogen (N) and sulfur (S) has increased dramatically over pre-industrial levels, with many potential impacts on terrestrial and aquatic ecosystems. Quantitative thresholds, termed "critical loads" (CLs), have been developed to estimate the deposition rate above which damage is thought to occur. However, there remains no comprehensive comparison of when, where, and over what time periods individual CLs have been exceeded. We addressed this knowledge gap by combining several published data sources for historical and contemporary deposition, and overlaying these on six CL types from the National Critical Loads Database (NCLDv2...
May 1, 2018: Ecological Applications: a Publication of the Ecological Society of America
Martin Riemer, Jonathan Shine, Thomas Wolbers
Cross-dimensional interference between spatial and temporal processing is well documented in humans, but the direction of these interactions remains unclear. The theory of metaphoric structuring states that space is the dominant concept influencing time perception, whereas time has little effect upon the perception of space. In contrast, theories proposing a common neuronal mechanism representing magnitudes argue for a symmetric interaction between space and time perception. Here, we investigated space-time interactions in realistic, large-scale virtual environments...
April 23, 2018: Hippocampus
Charles W Bangley, Lee Paramore, Simon Dedman, Roger A Rulifson
Estuaries function as important nursery and foraging habitats for many coastal species, including highly migratory sharks. Pamlico Sound, North Carolina, is one of the largest estuaries in the continental United States and provides a variety of potential habitats for sharks. In order to identify and spatially delineate shark habitats within Pamlico Sound, shark catch and environmental data were analyzed from the 2007-2014 North Carolina Division of Marine Fisheries (NCDMF) gillnet and longline surveys conducted within the estuary...
2018: PloS One
Jeremiah P Hartner, Laura A Schrader
Spatial memory processing requires functional interaction between the hippocampus and the medial entorhinal cortex (MEC). The grid cells of the MEC are most abundant in layer II and rely on a complex network of local inhibitory interneurons to generate spatial firing properties. Stress can cause spatial memory deficits in males, but the specific underlying mechanisms affecting the known memory pathways remain unclear. Stress activates both the autonomic nervous system and the hypothalamic-pituitary-adrenal axis to release norepinephrine (NE) and glucocorticoids, respectively...
2018: Frontiers in Synaptic Neuroscience
Julija Krupic, Marius Bauza, Stephen Burton, John O'Keefe
Grid cells are neurons active in multiple fields arranged in a hexagonal lattice and are thought to represent the "universal metric for space." However, they become nonhomogeneously distorted in polarized enclosures, which challenges this view. We found that local changes to the configuration of the enclosure induce individual grid fields to shift in a manner inversely related to their distance from the reconfigured boundary. The grid remained primarily anchored to the unchanged stable walls and showed a nonuniform rescaling...
March 9, 2018: Science
Karthik Soman, Vignesh Muralidharan, V Srinivasa Chakravarthy
Spatial cells in the hippocampal complex play a pivotal role in the navigation of an animal. Exact neural principles behind these spatial cell responses have not been completely unraveled yet. Here we present two models for spatial cells namely the Velocity Driven Oscillatory Network and Locomotor Driven Oscillatory Network. Both models have basically three stages in common such as direction encoding stage, path integration stage and a stage of unsupervised learning of path integration values. In the first model, the following three stages are implemented: head direction layer, frequency modulation by a layer of oscillatory neurons, and an unsupervised stage that extracts the Principal Components from the oscillator outputs...
March 25, 2018: European Journal of Neuroscience
Matthias Stangl, Johannes Achtzehn, Karin Huber, Caroline Dietrich, Claus Tempelmann, Thomas Wolbers
A progressive loss of navigational abilities in old age has been observed in numerous studies, but we have only limited understanding of the neural mechanisms underlying this decline [1]. A central component of the brain's navigation circuit are grid cells in entorhinal cortex [2], largely thought to support intrinsic self-motion-related computations, such as path integration (i.e., keeping track of one's position by integrating self-motion cues) [3-6]. Given that entorhinal cortex is particularly vulnerable to neurodegenerative processes during aging and Alzheimer's disease [7-14], deficits in grid cell function could be a key mechanism to explain age-related navigational decline...
March 12, 2018: Current Biology: CB
Bruce Palmer
This paper will describe a formalism for using correlation functions between different grid cells as the basis for determining coarse-grained hydrodynamic equations for modeling the behavior of mesoscopic fluid systems. Configurations from a molecular dynamics simulation or other atomistic simulation are projected onto basis functions representing grid cells in a continuum hydrodynamic simulation. Equilibrium correlation functions between different grid cells are evaluated from the molecular simulation and used to determine the evolution operator for the coarse-grained hydrodynamic system...
February 2018: Physical Review. E
Niklas Wilming, Peter König, Seth König, Elizabeth A Buffalo
Grid cells in the entorhinal cortex allow for the precise decoding of position in space. Along with potentially playing an important role in navigation, grid cells have recently been hypothesized to make a general contribution to mental operations. A prerequisite for this hypothesis is that grid cell activity does not critically depend on physical movement. Here, we show that movement of covert attention, without any physical movement, also elicits spatial receptive fields with a triangular tiling of space...
March 14, 2018: ELife
Caitlin S Mallory, Lisa M Giocomo
The discovery of place cells provided fundamental insight into the neural basis by which the hippocampus encodes spatial memories and supports navigation and prompted the development of computational models to explain the emergence of their spatial selectively. Many such works posit that input from entorhinal grid cells is critical to the formation of place fields, a prediction that has received mixed experimental support. Potentially reconciling seemingly conflicting findings is recent work indicating that subpopulations of pyramidal neurons are functionally distinct and may be driven to varying degrees by different inputs...
April 2018: Current Opinion in Neurobiology
K W Oleson, G B Anderson, B Jones, S A McGinnis, B Sanderson
Previous studies examining future changes in heat/cold waves using climate model ensembles have been limited to grid cell-average quantities. Here, we make use of an urban parameterization in the Community Earth System Model (CESM) that represents the urban heat island effect, which can exacerbate extreme heat but may ameliorate extreme cold in urban relative to rural areas. Heat/cold wave characteristics are derived for U.S. regions from a bias-corrected CESM 30-member ensemble for climate outcomes driven by the RCP8...
February 2018: Climatic Change
Robert Naumann, Patricia Preston-Ferrer, Michael Brecht, Andrea Burgalossi
Following the groundbreaking discovery of grid cells, the medial entorhinal cortex (MEC) has become the focus of intense anatomical, physiological, and computational investigations. Whether and how grid activity maps onto cell types and cortical architecture is still an open question. Fundamental similarities in microcircuits, function and connectivity suggest a homology between rodent MEC and human posteromedial entorhinal cortex. Both are specialized for spatial processing and display similar cellular organization, consisting of layer 2 pyramidal/calbindin cell patches superimposed on scattered stellate neurons...
March 7, 2018: Journal of Neurophysiology
Chiara Badaloni, Giorgio Cattani, Francesca De' Donato, Alessandra Gaeta, Gianluca Leone, Paola Michelozzi, Marina Davoli, Francesco Forastiere, Massimo Stafoggia
OBJECTIVES: to define a national geographic domain, with high spatial (1 km²) and temporal (daily) resolution, and to build a list of georeferenced environmental and temporal indicators useful for environmental epidemiology applications at national level. DESIGN: geographic study. SETTING AND PARTICIPANTS: study domain: Italian territory divided into 307,635 1-km² grid cells; study period: 2006-2012, divided into 2,557 daily time windows...
January 2018: Epidemiologia e Prevenzione
Justin Lessler, Sean M Moore, Francisco J Luquero, Heather S McKay, Rebecca Grais, Myriam Henkens, Martin Mengel, Jessica Dunoyer, Maurice M'bangombe, Elizabeth C Lee, Mamoudou Harouna Djingarey, Bertrand Sudre, Didier Bompangue, Robert S M Fraser, Abdinasir Abubakar, William Perea, Dominique Legros, Andrew S Azman
BACKGROUND: Cholera remains a persistent health problem in sub-Saharan Africa and worldwide. Cholera can be controlled through appropriate water and sanitation, or by oral cholera vaccination, which provides transient (∼3 years) protection, although vaccine supplies remain scarce. We aimed to map cholera burden in sub-Saharan Africa and assess how geographical targeting could lead to more efficient interventions. METHODS: We combined information on cholera incidence in sub-Saharan Africa (excluding Djibouti and Eritrea) from 2010 to 2016 from datasets from WHO, Médecins Sans Frontières, ProMED, ReliefWeb, ministries of health, and the scientific literature...
March 1, 2018: Lancet
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