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https://www.readbyqxmd.com/read/29333481/theta-sequences-of-grid-cell-populations-can-provide-a-movement-direction-signal
#1
Ipshita Zutshi, Jill K Leutgeb, Stefan Leutgeb
It has been proposed that path integration in mammals is performed by the convergence of internally generated speed and directional inputs onto grid cells. Although this hypothesis has been supported by the discovery that head direction, speed, and grid cells are intermixed within entorhinal cortex and by the recent finding that head-direction inputs are necessary for grid firing, many details on how grid cells are generated have remained elusive. For example, analysis of recording data suggests that substituting head direction for movement direction accrues errors that preclude the formation of grid patterns...
October 2017: Current Opinion in Behavioral Sciences
https://www.readbyqxmd.com/read/29311746/hexadirectional-coding-of-visual-space-in-human-entorhinal-cortex
#2
Matthias Nau, Tobias Navarro Schröder, Jacob L S Bellmund, Christian F Doeller
Entorhinal grid cells map the local environment, but their involvement beyond spatial navigation remains elusive. We examined human functional MRI responses during a highly controlled visual tracking task and show that entorhinal cortex exhibited a sixfold rotationally symmetric signal encoding gaze direction. Our results provide evidence for a grid-like entorhinal code for visual space and suggest a more general role of the entorhinal grid system in coding information along continuous dimensions.
January 8, 2018: Nature Neuroscience
https://www.readbyqxmd.com/read/29276476/critical-points-and-traveling-wave-in-locomotion-experimental-evidence-and-some-theoretical-considerations
#3
REVIEW
Philippe Saltiel, Andrea d'Avella, Matthew C Tresch, Kuno Wyler, Emilio Bizzi
The central pattern generator (CPG) architecture for rhythm generation remains partly elusive. We compare cat and frog locomotion results, where the component unrelated to pattern formation appears as a temporal grid, and traveling wave respectively. Frog spinal cord microstimulation with N-methyl-D-Aspartate (NMDA), a CPG activator, produced a limited set of force directions, sometimes tonic, but more often alternating between directions similar to the tonic forces. The tonic forces were topographically organized, and sites evoking rhythms with different force subsets were located close to the constituent tonic force regions...
2017: Frontiers in Neural Circuits
https://www.readbyqxmd.com/read/29230055/impaired-path-integration-in-mice-with-disrupted-grid-cell-firing
#4
Mariana Gil, Mihai Ancau, Magdalene I Schlesiger, Angela Neitz, Kevin Allen, Rodrigo J De Marco, Hannah Monyer
Path integration (PI) is a highly conserved, self-motion-based navigation strategy. Since the discovery of grid cells in the medial entorhinal cortex, neurophysiological data and computational models have suggested that these neurons serve PI. However, more direct empirical evidence supporting this hypothesis has been missing due to a lack of selective manipulations of grid cell activity and suitable behavioral assessments. Here we report that selective disruption of grid cell activity in mice can be achieved by removing NMDA glutamate receptors from the retro-hippocampal region and that disrupted grid cell firing accounts for impaired PI performance...
January 2018: Nature Neuroscience
https://www.readbyqxmd.com/read/29230051/integration-of-grid-maps-in-merged-environments
#5
Tanja Wernle, Torgeir Waaga, Maria Mørreaunet, Alessandro Treves, May-Britt Moser, Edvard I Moser
Natural environments are represented by local maps of grid cells and place cells that are stitched together. The manner by which transitions between map fragments are generated is unknown. We recorded grid cells while rats were trained in two rectangular compartments, A and B (each 1 m × 2 m), separated by a wall. Once distinct grid maps were established in each environment, we removed the partition and allowed the rat to explore the merged environment (2 m × 2 m). The grid patterns were largely retained along the distal walls of the box...
January 2018: Nature Neuroscience
https://www.readbyqxmd.com/read/29218403/the-storage-and-recall-of-memories-in-the-hippocampo-cortical-system
#6
REVIEW
Edmund T Rolls
A quantitative computational theory of the operation of the hippocampus as an episodic memory system is described. The CA3 system operates as a single attractor or autoassociation network (1) to enable rapid one-trial associations between any spatial location (place in rodents or spatial view in primates) and an object or reward and (2) to provide for completion of the whole memory during recall from any part. The theory is extended to associations between time and object or reward to implement temporal order memory, which is also important in episodic memory...
December 7, 2017: Cell and Tissue Research
https://www.readbyqxmd.com/read/29216467/drivers-of-dissolved-organic-carbon-export-in-a-subarctic-catchment-importance-of-microbial-decomposition-sorption-desorption-peatland-and-lateral-flow
#7
Jing Tang, Alla Y Yurova, Guy Schurgers, Paul A Miller, Stefan Olin, Benjamin Smith, Matthias B Siewert, David Olefeldt, Petter Pilesjö, Anneli Poska
Tundra soils account for 50% of global stocks of soil organic carbon (SOC), and it is expected that the amplified climate warming in high latitude could cause loss of this SOC through decomposition. Decomposed SOC could become hydrologically accessible, which increase downstream dissolved organic carbon (DOC) export and subsequent carbon release to the atmosphere, constituting a positive feedback to climate warming. However, DOC export is often neglected in ecosystem models. In this paper, we incorporate processes related to DOC production, mineralization, diffusion, sorption-desorption, and leaching into a customized arctic version of the dynamic ecosystem model LPJ-GUESS in order to mechanistically model catchment DOC export, and to link this flux to other ecosystem processes...
December 4, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/29213234/cognitive-mapping-based-on-conjunctive-representations-of-space-and-movement
#8
Taiping Zeng, Bailu Si
It is a challenge to build robust simultaneous localization and mapping (SLAM) system in dynamical large-scale environments. Inspired by recent findings in the entorhinal-hippocampal neuronal circuits, we propose a cognitive mapping model that includes continuous attractor networks of head-direction cells and conjunctive grid cells to integrate velocity information by conjunctive encodings of space and movement. Visual inputs from the local view cells in the model provide feedback cues to correct drifting errors of the attractors caused by the noisy velocity inputs...
2017: Frontiers in Neurorobotics
https://www.readbyqxmd.com/read/29196525/mapping-local-and-global-variability-in-plant-trait-distributions
#9
Ethan E Butler, Abhirup Datta, Habacuc Flores-Moreno, Ming Chen, Kirk R Wythers, Farideh Fazayeli, Arindam Banerjee, Owen K Atkin, Jens Kattge, Bernard Amiaud, Benjamin Blonder, Gerhard Boenisch, Ben Bond-Lamberty, Kerry A Brown, Chaeho Byun, Giandiego Campetella, Bruno E L Cerabolini, Johannes H C Cornelissen, Joseph M Craine, Dylan Craven, Franciska T de Vries, Sandra Díaz, Tomas F Domingues, Estelle Forey, Andrés González-Melo, Nicolas Gross, Wenxuan Han, Wesley N Hattingh, Thomas Hickler, Steven Jansen, Koen Kramer, Nathan J B Kraft, Hiroko Kurokawa, Daniel C Laughlin, Patrick Meir, Vanessa Minden, Ülo Niinemets, Yusuke Onoda, Josep Peñuelas, Quentin Read, Lawren Sack, Brandon Schamp, Nadejda A Soudzilovskaia, Marko J Spasojevic, Enio Sosinski, Peter E Thornton, Fernando Valladares, Peter M van Bodegom, Mathew Williams, Christian Wirth, Peter B Reich
Our ability to understand and predict the response of ecosystems to a changing environment depends on quantifying vegetation functional diversity. However, representing this diversity at the global scale is challenging. Typically, in Earth system models, characterization of plant diversity has been limited to grouping related species into plant functional types (PFTs), with all trait variation in a PFT collapsed into a single mean value that is applied globally. Using the largest global plant trait database and state of the art Bayesian modeling, we created fine-grained global maps of plant trait distributions that can be applied to Earth system models...
December 1, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29190508/evaluation-of-sediment-and-137cs-redistribution-in-the-oginosawa-river-catchment-near-the-fukushima-dai-ichi-nuclear-power-plant-using-integrated-watershed-modeling
#10
Kazuyuki Sakuma, Alex Malins, Hironori Funaki, Hiroshi Kurikami, Tadafumi Niizato, Takahiro Nakanishi, Koji Mori, Kazuhiro Tada, Takamaru Kobayashi, Akihiro Kitamura, Masaaki Hosomi
The Oginosawa River catchment lies 15 km south-west of the Fukushima Dai-ichi nuclear plant and covers 7.7 km2. Parts of the catchment were decontaminated between fall 2012 and March 2014 in preparation for the return of the evacuated population. The General-purpose Terrestrial Fluid-flow Simulator (GETFLOWS) code was used to study sediment and 137Cs redistribution within the catchment, including the effect of decontamination on redistribution. Fine resolution grid cells were used to model local features of the catchment, such as paddy fields adjacent to the Oginosawa River...
November 27, 2017: Journal of Environmental Radioactivity
https://www.readbyqxmd.com/read/29176562/understanding-heat-patterns-produced-by-vehicular-flows-in-urban-areas
#11
Rui Zhu, Man Sing Wong, Éric Guilbert, Pak-Wai Chan
Vehicular traffic has strong implication in the severity and degree of Urban Heat Island (UHI) effect in a city. It is crucial to map and monitor the spatio-temporal heat patterns from vehicular traffic in a city. Data observed from traffic counting stations are readily available for mapping the traffic-related heat across the stations. However, macroscopic models utilizing traffic counting data to estimate dynamic directional vehicular flows are rarely established. Our work proposes a simple and robust cell-transmission-model to simulate all the possible cell-based origin-destination trajectories of vehicular flows over time, based on the traffic counting stations...
November 24, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29153321/consistency-of-spatial-representations-in-rat-entorhinal-cortex-predicts-performance-in-a-reorientation-task
#12
Shahaf Weiss, Ghadeer Talhami, Xenia Gofman-Regev, Sophia Rapoport, David Eilam, Dori Derdikman
Goal-directed behavior can be affected by environmental geometry. A classic example is the rectangular arena reorientation task, where subjects commonly confuse opposite but geometrically identical corners [1]. Until recently, little was known about how environmental geometry shapes spatial representations in a neurobehavioral context [2] (although see [3]). In the present study, we asked: Under what circumstances does the internal cognitive map predict behavior? And when does it fail to do so? To this end, we developed a variant of the classical reorientation task that allows for investigation of temporal dynamics of reorientation...
November 9, 2017: Current Biology: CB
https://www.readbyqxmd.com/read/29152817/how-complex-should-models-be-comparing-correlative-and-mechanistic-range-dynamics-models
#13
Damien A Fordham, Cleo Bertelsmeier, Barry W Brook, Regan Early, Dora Neto, Stuart C Brown, Sébastien Ollier, Miguel B Araújo
Criticism has been levelled at climate-change-induced forecasts of species range shifts that do not account explicitly for complex population dynamics. The relative importance of such dynamics under climate change is, however, undetermined because direct tests comparing the performance of demographic models vs. simpler ecological niche models are still lacking owing to difficulties in evaluating forecasts using real-world data. We provide the first comparison of the skill of coupled ecological-niche-population models and ecological niche models in predicting documented shifts in the ranges of 20 British breeding bird species across a 40-year period...
November 20, 2017: Global Change Biology
https://www.readbyqxmd.com/read/29151838/observation-and-model-based-estimates-of-particulate-dry-nitrogen-deposition-to-the-oceans
#14
Alex R Baker, Maria Kanakidou, Katye E Altieri, Nikos Daskalakis, Gregory S Okin, Stelios Myriokefalitakis, Frank Dentener, Mitsuo Uematsu, Manmohan M Sarin, Robert A Duce, James N Galloway, William C Keene, Arvind Singh, Lauren Zamora, Jean-Francois Lamarque, Shih-Chieh Hsu, Shital S Rohekar, Joseph M Prospero
Anthropogenic nitrogen (N) emissions to the atmosphere have increased significantly the deposition of nitrate (NO3(-)) and ammonium (NH4(+)) to the surface waters of the open ocean, with potential impacts on marine productivity and the global carbon cycle. Global-scale understanding of the impacts of N deposition to the oceans is reliant on our ability to produce and validate models of nitrogen emission, atmospheric chemistry, transport and deposition. In this work, ~2900 observations of aerosol NO3(-) and NH4(+) concentrations, acquired from sampling aboard ships in the period 1995 - 2012, are used to assess the performance of modelled N concentration and deposition fields over the remote ocean...
2017: Atmospheric Chemistry and Physics
https://www.readbyqxmd.com/read/29134013/southern-ocean-echinoids-database-an-updated-version-of-antarctic-sub-antarctic-and-cold-temperate-echinoid-database
#15
Salomé Fabri-Ruiz, Thomas Saucède, Bruno Danis, Bruno David
This database includes over 7,100 georeferenced occurrence records of sea urchins (Echinodermata: Echinoidea) obtained from samples collected in the Southern Ocean (+180°W/+180°E; -35°/-78°S) during oceanographic cruises led over 150 years, from 1872 to 2015. Echinoids are common organisms of Southern Ocean benthic communities. A total of 201 species is recorded, which display contrasting depth ranges and distribution patterns across austral provinces and bioregions. Echinoid species show various ecological traits including different nutrition and reproductive strategies...
2017: ZooKeys
https://www.readbyqxmd.com/read/29111257/a-catchment-scale-model-to-predict-spatial-and-temporal-burden-of-e-coli-on-pasture-from-grazing-livestock
#16
David M Oliver, Phil J Bartie, A Louise Heathwaite, Sim M Reaney, Jared A Q Parnell, Richard S Quilliam
Effective management of diffuse microbial water pollution from agriculture requires a fundamental understanding of how spatial patterns of microbial pollutants, e.g. E. coli, vary over time at the landscape scale. The aim of this study was to apply the Visualising Pathogen &Environmental Risk (ViPER) model, developed to predict E. coli burden on agricultural land, in a spatially distributed manner to two contrasting catchments in order to map and understand changes in E. coli burden contributed to land from grazing livestock...
October 27, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/29109512/modulating-medial-septal-cholinergic-activity-reduces-medial-entorhinal-theta-frequency-without-affecting-speed-or-grid-coding
#17
Francis Carpenter, Neil Burgess, Caswell Barry
Medial septal inputs to the hippocampal system are crucial for aspects of temporal and spatial processing, such as theta oscillations and grid cell firing. However, the precise contributions of the medial septum's cholinergic neurones to these functions remain unknown. Here, we recorded neuronal firing and local field potentials from the medial entorhinal cortex of freely foraging mice, while modulating the excitability of medial septal cholinergic neurones. Alteration of cholinergic activity produced a reduction in the frequency of theta oscillations, without affecting the slope of the non-linear theta frequency vs running speed relationship observed...
November 6, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29097084/exposure-to-fine-particulate-matter-during-pregnancy-and-risk-of-term-low-birth-weight-in-jinan-china-2014-2016
#18
Han Wu, Baofa Jiang, Xingyi Geng, Ping Zhu, Zhong Liu, Liangliang Cui, Liping Yang
BACKGROUND: Existing studies exploring the association between low birth weight (LBW) and maternal fine particulate matter (aerodynamic diameter<2.5μm, PM2.5) exposure have presented equivocal results, and one of the possible reasons for this finding might be due to relatively low maternal exposures. In addition, relatively narrow maternal exposure windows to PM2.5 have not been well established for LBW. METHODS: We employed a nested matched case-control design among 43,855 term births in a large maternity and child care hospital in Jinan, China...
October 28, 2017: International Journal of Hygiene and Environmental Health
https://www.readbyqxmd.com/read/29075993/grid-mapping-a-novel-method-of-signal-quality-evaluation-on-a-single-lead-electrocardiogram
#19
Yanjun Li, Xiaoying Tang
Diagnosis of long-term electrocardiogram (ECG) calls for automatic and accurate methods of ECG signal quality estimation, not only to lighten the burden of the doctors but also to avoid misdiagnoses. In this paper, a novel waveform-based method of phase-space reconstruction for signal quality estimation on a single lead ECG was proposed by projecting the amplitude of the ECG and its first order difference into grid cells. The waveform of a single lead ECG was divided into non-overlapping episodes (Ts = 10, 20, 30 s), and the number of grids in both the width and the height of each map are in the range [20, 100] (NX = NY = 20, 30, 40, … 90, 100)...
October 26, 2017: Australasian Physical & Engineering Sciences in Medicine
https://www.readbyqxmd.com/read/29073644/spatial-representation-in-the-hippocampal-formation-a-history
#20
REVIEW
Edvard I Moser, May-Britt Moser, Bruce L McNaughton
Since the first place cell was recorded and the cognitive-map theory was subsequently formulated, investigation of spatial representation in the hippocampal formation has evolved in stages. Early studies sought to verify the spatial nature of place cell activity and determine its sensory origin. A new epoch started with the discovery of head direction cells and the realization of the importance of angular and linear movement-integration in generating spatial maps. A third epoch began when investigators turned their attention to the entorhinal cortex, which led to the discovery of grid cells and border cells...
October 26, 2017: Nature Neuroscience
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