Read by QxMD icon Read

"Grid cells"

Anna Jafarpour, Hugo Spiers
When humans draw maps, or make judgments about travel-time, their responses are rarely accurate and are often systematically distorted. Distortion effects on estimating time to arrival and the scale of sketch-maps reveal the nature of mental representation of time and space. Inspired by data from rodent entorhinal grid cells, we predicted that familiarity to an environment would distort representations of the space by expanding the size of it. We also hypothesized that travel-time estimation would be distorted in the same direction as space-size, if time and space rely on the same cognitive map...
October 22, 2016: Hippocampus
Alexandra Cucoş Dinu, Botond Papp, Tiberius Dicu, Mircea Moldovan, Denissa Bety Burghele, Ionuţ Tudor Moraru, Ancuţa Tenţer, Constantin Cosma
The exposure to radon and radon decay products in homes and at workplaces represents the greatest risk from natural ionizing radiation. The present study brings forward the residential, soil and water radon surveys in 5 counties of Romania. Indoor radon measurements were performed by using CR-39 track detectors exposed for 3 months on ground-floor level of dwellings, according to the NRPB Measurements Protocol. Radon concentrations in soil and water were measured using the LUK3C device. The indoor radon concentrations ranged from 5 to 2592 Bq⋅m(-3) with an updated preliminary arithmetic mean of 133 Bq⋅m(-3), and a geometric mean of 90 Bq⋅m(-3)...
October 17, 2016: Journal of Environmental Radioactivity
Nikolaus Kriegeskorte, Katherine R Storrs
"Grid cells" encode an animal's location and direction of movement in 2D physical environments via regularly repeating receptive fields. Constantinescu et al. (2016) report the first evidence of grid cells for 2D conceptual spaces. The work has exciting implications for mental representation and shows how detailed neural-coding hypotheses can be tested with bulk population-activity measures.
October 19, 2016: Neuron
Yongseok Yoo, Woori Kim
Neural systems are inherently noisy. One well-studied example of a noise reduction mechanism in the brain is the population code, where representing a variable with multiple neurons allows the encoded variable to be recovered with fewer errors. Studies have assumed ideal observer models for decoding population codes, and the manner in which information in the neural population can be retrieved remains elusive. This letter addresses a mechanism by which realistic neural circuits can recover encoded variables...
October 20, 2016: Neural Computation
William Severa, Ojas Parekh, Conrad D James, James B Aimone
The dentate gyrus forms a critical link between the entorhinal cortex and CA3 by providing a sparse version of the signal. Concurrent with this increase in sparsity, a widely accepted theory suggests the dentate gyrus performs pattern separation-similar inputs yield decorrelated outputs. Although an active region of study and theory, few logically rigorous arguments detail the dentate gyrus's (DG) coding. We suggest a theoretically tractable, combinatorial model for this action. The model provides formal methods for a highly redundant, arbitrarily sparse, and decorrelated output signal...
October 20, 2016: Neural Computation
J Augustin, J Austermann, S Erasmi
Background: One of the overall objectives of the legislator is to ensure an overall "homogeneous", and easily accessible medical care for the population. The physician-patient ratio can be used to describe the regional health care situation. But this method does not provide information concerning the availability of, for instance, the nearest doctor. Therefore, further parameters such as accessibility must be taken into consideration. For this purpose, network analyses are an appropriate method. The objective of this study is to present methodological tools to evaluate the healthcare situation in the metropolitan region of Hamburg, primarily focusing on accessibility using dermatologists as an example...
October 18, 2016: Das Gesundheitswesen
R Behnke, S Vavrus, A Allstadt, T Albright, W E Thogmartin, V C Radeloff
Weather and climate affect many ecological processes, making spatially continuous yet fine-resolution weather data desirable for ecological research and predictions. Numerous downscaled weather data sets exist, but little attempt has been made to evaluate them systematically. Here we address this shortcoming by focusing on four major questions: (1) How accurate are downscaled, gridded climate data sets in terms of temperature and precipitation estimates? (2) Are there significant regional differences in accuracy among data sets? (3) How accurate are their mean values compared with extremes? (4) Does their accuracy depend on spatial resolution? We compared eight widely used downscaled data sets that provide gridded daily weather data for recent decades across the United States...
July 2016: Ecological Applications: a Publication of the Ecological Society of America
Yuting Zhou, Xiangming Xiao, Yuanwei Qin, Jinwei Dong, Geli Zhang, Weili Kou, Cui Jin, Jie Wang, Xiangping Li
Accurate and up-to-date information on the spatial distribution of paddy rice fields is necessary for the studies of trace gas emissions, water source management, and food security. The phenology-based paddy rice mapping algorithm, which identifies the unique flooding stage of paddy rice, has been widely used. However, identification and mapping of paddy rice in rice-wetland coexistent areas is still a challenging task. In this study, we found that the flooding/transplanting periods of paddy rice and natural wetlands were different...
April 2016: International Journal of Applied Earth Observation and Geoinformation: ITC Journal
Holger Dannenberg, James R Hinman, Michael E Hasselmo
Behavioral data suggest that cholinergic modulation may play a role in certain aspects of spatial memory, and neurophysiological data demonstrate neurons that fire in response to spatial dimensions, including grid cells and place cells that respond on the basis of location and running speed. These neurons show firing responses that depend upon the visual configuration of the environment, due to coding in visually-responsive regions of the neocortex. This review focuses on the physiological effects of acetylcholine that may influence the sensory coding of spatial dimensions relevant to behavior...
September 24, 2016: Journal of Physiology, Paris
Argo Ronk, Francesco de Bello, Pavel Fibich, Meelis Pärtel
Large-scale biodiversity studies can be more informative if observed diversity in a study site is accompanied by dark diversity, the set of absent although ecologically suitable species. Dark diversity methodology is still being developed and a comparison of different approaches is needed. We used plant data at two different scales (European and seven large regions) and compared dark diversity estimates from two mathematical methods: species co-occurrence (SCO) and species distribution modeling (SDM). We used plant distribution data from the Atlas Florae Europaeae (50 × 50 km grid cells) and seven different European regions (10 × 10 km grid cells)...
September 2016: Ecology and Evolution
Georgios Gerogiokas, Michelle W Y Southey, Michael P Mazanetz, Alexander Heifetz, Michael Bodkin, Richard J Law, Richard H Henchman, J Michel
Molecular dynamics simulations have been analyzed with the Grid Cell Theory (GCT) method to spatially resolve the binding enthalpies and entropies of water molecules at the interface of 17 structurally diverse proteins. Correlations between computed energetics and structural descriptors have been sought to facilitate the development of simple models of protein hydration. Little correlation was found between GCT-computed binding enthalpies and continuum electrostatics calculations. A simple count of contacts with functional groups in charged amino acids correlates well with enhanced water stabilization, but the stability of water near hydrophobic and polar residues depends markedly on its coordination environment...
October 13, 2016: Journal of Physical Chemistry. B
Corinna S Bazelet, Aileen C Thompson, Piotr Naskrecki
The use of endemism and vascular plants only for biodiversity hotspot delineation has long been contested. Few studies have focused on the efficacy of global biodiversity hotspots for the conservation of insects, an important, abundant, and often ignored component of biodiversity. We aimed to test five alternative diversity measures for hotspot delineation and examine the efficacy of biodiversity hotspots for conserving a non-typical target organism, South African katydids. Using a 1° fishnet grid, we delineated katydid hotspots in two ways: (1) count-based: grid cells in the top 10% of total, endemic, threatened and/or sensitive species richness; vs...
2016: PloS One
Marie Hébert, Antoine Anfray, Arnaud Chevilley, Sara Martinez de Lizarrondo, Aurélien Quenault, Morgane Louessard, Benoit D Roussel, Pauline Obiang, Etienne Save, Cyrille Orset, Eric Maubert, Denis Vivien, Véronique Agin
In humans, spatial cognition and navigation impairments are a frequent situation during physiological and pathological aging, leading to a dramatic deterioration in the quality of life. Despite the discovery of neurons with location-specific activity in rodents, that is, place cells in the hippocampus and later on grid cells in the entorhinal cortex (EC), the molecular mechanisms underlying spatial cognition are still poorly known. Our present data bring together in an unusual combination 2 molecules of primary biological importance: a major neuronal excitatory receptor, N-methyl-D-aspartate receptor (NMDAR), and an extracellular protease, tissue plasminogen activator (tPA), in the control of spatial navigation...
September 9, 2016: Cerebral Cortex
Fotis Georgiou, Maarten Hornikx
The pseudospectral time-domain method (PSTD) provides an efficient way to solve the linear acoustics equations. With regards to acoustic modeling and auralization, source directivity as well as head-related directivity have a clear influence on the perceived sound field and have to be included in computations. In this paper directive sources are implemented in the time-domain method PSTD. First, a given frequency dependent source directivity is decomposed onto spherical harmonic functions. The directive source is then implemented through spatial distributions in PSTD that relate to the spherical harmonic functions, and time-dependent functions are assigned to the spatial distributions in order to obtain the frequency content of the directivity...
August 2016: Journal of the Acoustical Society of America
Jacob Ls Bellmund, Lorena Deuker, Tobias Navarro Schröder, Christian F Doeller
Anticipating the future is a key motif of the brain, possibly supported by mental simulation of upcoming events. Rodent single-cell recordings suggest the ability of spatially tuned cells to represent subsequent locations. Grid-like representations have been observed in the human entorhinal cortex during virtual and imagined navigation. However, hitherto it remains unknown if grid-like representations contribute to mental simulation in the absence of imagined movement. Participants imagined directions between building locations in a large-scale virtual-reality city while undergoing fMRI without re-exposure to the environment...
2016: ELife
Iyad Kheirbek, Jay Haney, Sharon Douglas, Kazuhiko Ito, Thomas Matte
BACKGROUND: On-road vehicles are an important source of fine particulate matter (PM2.5) in cities, but spatially varying traffic emissions and vulnerable populations make it difficult to assess impacts to inform policy and the public. METHODS: We estimated PM2.5-attributable mortality and morbidity from on-road vehicle generated air pollution in the New York City (NYC) region using high-spatial-resolution emissions estimates, air quality modeling, and local health incidence data to evaluate variations in impacts by vehicle class, neighborhood, and area socioeconomic status...
2016: Environmental Health: a Global Access Science Source
Christoph Hönigsperger, Maximiliano J Nigro, Johan F Storm
The medial entorhinal cortex (mEC) is strongly involved in spatial navigation, memory, dementia and epilepsy. Although potassium channels shape neuronal activity, their roles in mEC are largely unknown. We used the new Kv2 blocker Guangxitoxin-1E (GTx, 10-100 nm) in rat brain slices to investigate Kv2 channel functions in mEC layer II stellate cells (SCs). These neurons project to the hippocampus and are thought to be grid cells representing space. Voltage clamp recordings from SCs nucleated patches showed that GTx inhibited a delayed rectifier K(+) current activating beyond -30 mV, but not transient, A-type current...
August 26, 2016: Journal of Physiology
Caterina Penone, Ben G Weinstein, Catherine H Graham, Thomas M Brooks, Carlo Rondinini, S Blair Hedges, Ana D Davidson, Gabriel C Costa
The taxonomic, phylogenetic and trait dimensions of beta diversity each provide us unique insights into the importance of historical isolation and environmental conditions in shaping global diversity. These three dimensions should, in general, be positively correlated. However, if similar environmental conditions filter species with similar trait values, then assemblages located in similar environmental conditions, but separated by large dispersal barriers, may show high taxonomic, high phylogenetic, but low trait beta diversity...
August 31, 2016: Proceedings. Biological Sciences
Matthew J Troia, Ryan A McManamay
Primary biodiversity data constitute observations of particular species at given points in time and space. Open-access electronic databases provide unprecedented access to these data, but their usefulness in characterizing species distributions and patterns in biodiversity depend on how complete species inventories are at a given survey location and how uniformly distributed survey locations are along dimensions of time, space, and environment. Our aim was to compare completeness and coverage among three open-access databases representing ten taxonomic groups (amphibians, birds, freshwater bivalves, crayfish, freshwater fish, fungi, insects, mammals, plants, and reptiles) in the contiguous United States...
July 2016: Ecology and Evolution
Brett J Tunno, Jessie L C Shmool, Drew R Michanowicz, Sheila Tripathy, Lauren G Chubb, Ellen Kinnee, Leah Cambal, Courtney Roper, Jane E Clougherty
Capturing intra-urban variation in diesel-related pollution exposures remains a challenge, given its complex chemical mix, and relatively few well-characterized ambient-air tracers for the multiple diesel sources in densely-populated urban areas. To capture fine-scale spatial resolution (50×50m grid cells) in diesel-related pollution, we used geographic information systems (GIS) to systematically allocate 36 sampling sites across downtown Pittsburgh, PA, USA (2.8km(2)), cross-stratifying to disentangle source impacts (i...
August 18, 2016: Science of the Total Environment
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"