How local is the local field potential?

Local field potentials (LFPs) are of growing importance in neurophysiological investigations. LFPs supplement action potential recordings by indexing activity relevant to EEG, magnetoencephalographic, and hemodynamic (fMRI) signals. Recent reports suggest that LFPs reflect activity within very small domains of several hundred micrometers. We examined this conclusion by comparing LFP, current source density (CSD), and multiunit activity (MUA) signals in macaque auditory cortex. Estimated by frequency tuning bandwidths, these signals' "listening areas" differ systematically with an order of MUA?< CSD?< LFP. Computational analyses confirm that observed LFPs receive local contributions. Direct measurements indicate passive spread of LFPs to sites more than a centimeter from their origins. These findings appear to be independent of the frequency content of the LFP. Our results challenge the idea that LFP recordings typically integrate over extremely circumscribed local domains. Rather, LFPs appear as a mixture of local potentials with "volume conducted" potentials from distant sites.     

Antibacterial immunity of lower airways: local or localized?

Clearance of bacteria in the bronchoalveolar lavage, the level and functional activity of IgA and changes in the cellular composition of BAL were examined in mice after supralaryngeal immunization and subsequent challenge with Klebsiella pneumoniae. More than 60% of the bacterial inoculum was removed by nonspecific mechanisms within 90 min after inoculation; within the time interval 1.5-3.5 h, clearance was significantly accelerated in locally immunized mice. The enhancement of clearance effectiveness is specific and increases proportionally with the length of immunization (1 less than 2 less than 4 weeks); it is of short duration and towards the end of the 3rd week after immunization, in 73% of immunized animals, the clearance values did not differ from values found in controls. The local immunization did not influence the total level of IgA in BAL, the formation of specific IgA antibody was minimal, in vivo binding of IgA to klebsiella could not be demonstrated. In immunized mice, a significant increase in the numbers of PMN and lymphocytes, as well as an increased activity of phagocytic cell (PMN, MP) was found in BAL. The time interval of 1.5-3.5 h after challenge bounds the space for mechanisms, activated by local immunization in lower airways. The actual participation of individual factors in the accelerated elimination of bacteria from the lumen of airways, remains unclear so far.     

Cordia millenii: on the risk of local extinction?

Selective logging of valuable tropical timber trees is a conservation concern because it threatens the long-term sustainability of forests. However, there is insufficient information regarding the postlogging recovery of harvested species. Here, I assessed the seed dispersal patterns, recruitment and abundance of Cordia millenii , a valuable timber tree in two Ugandan tropical rain forests that have been subjected to varying disturbance regimes. The aim was to determine the vulnerability of Cordia in these forests. The rate of seed dispersal was lower in the heavily disturbed Mabira Forest compared with the less disturbed Budongo Forest. Frugivores in Mabira were small-bodied individuals that spat seeds beneath fruiting trees, whereas 90% of the fruit in Budongo was consumed by large-bodied chimpanzees that disperse seeds over long distances. Juveniles of Cordia were not found in the closed forest, although they were found in forest gaps in Budongo but not Mabira. Mature tree density was higher in Budongo compared with Mabira. Lack of effective seed dispersal coupled with the inability of seedlings of Cordia to establish under closed canopy account for the arrested recruitment in Mabira. Enrichment planting in felling gaps is necessary to avoid local extinction of Cordia in forests without large vertebrates.     

Glowworm swarm optimization for simultaneous capture of multiple local optima of multimodal functions

This paper presents glowworm swarm optimization (GSO), a novel algorithm for the simultaneous computation of multiple optima of multimodal functions. The algorithm shares a few features with some better known swarm intelligence based optimization algorithms, such as ant colony optimization and particle swarm optimization, but with several significant differences. The agents in GSO are thought of as glowworms that carry a luminescence quantity called luciferin along with them. The glowworms encode the fitness of their current locations, evaluated using the objective function, into a luciferin value that they broadcast to their neighbors. The glowworm identifies its neighbors and computes its movements by exploiting an adaptive neighborhood, which is bounded above by its sensor range. Each glowworm selects, using a probabilistic mechanism, a neighbor that has a luciferin value higher than its own and moves toward it. These movements—based only on local information and selective neighbor interactions—enable the swarm of glowworms to partition into disjoint subgroups that converge on multiple optima of a given multimodal function. We provide some theoretical results related to the luciferin update mechanism in order to prove the bounded nature and convergence of luciferin levels of the glowworms. Experimental results demonstrate the efficacy of the proposed glowworm based algorithm in capturing multiple optima of a series of standard multimodal test functions and more complex ones, such as stair-case and multiple-plateau functions. We also report the results of tests in higher dimensional spaces with a large number of peaks. We address the parameter selection problem by conducting experiments to show that only two parameters need to be selected by the user. Finally, we provide some comparisons of GSO with PSO and an experimental comparison with Niche-PSO, a PSO variant that is designed for the simultaneous computation of multiple optima. This work is partially supported by a project grant from the Ministry of Human Resources Development, India and by DRDO-IISc Mathematical Engineering Program.     

Conservation of remnant populations of Colchicum autumnale – The relative importance of local habitat quality and habitat fragmentation

Semi-natural habitat is extremely vulnerable to habitat fragmentation and degradation since its socio-economic value has decreased substantially during the last century in most parts of Europe. We evaluated the relative effects of habitat fragmentation and local environmental conditions on population structure and reproductive performance of the long-lived corm geophyte Colchicum autumnale in 17 highly fragmented populations. Habitat isolation did not affect patch occupancy, population structure or plant performance. In contrast, population size and local environment strongly affected population structure and reproductive performance. Densities of all life stages increased with increasing population size. Large populations also showed a higher reproductive performance and a larger proportion of new recruits. Relationships with local growth conditions pointed towards the importance of an open grassland sward for flower and fruit set and the presence of microsites for successful sexual recruitment. These results suggest that the distribution of C. autumnale consists of an assemblage of basically unconnected populations that are remnants of formerly larger populations. This is in accordance with the species' ability to grow clonally, allowing long-term persistence under deteriorating conditions that occurred during a long period of habitat fragmentation. In conclusion, our results indicate that local habitat and population size are more important than habitat fragmentation (i.e. calcareous grassland isolation and surface area) and argue in favour of a management that is primarily focused on local habitat restoration. This is preferentially accomplished by reintroducing grazing practices, complemented by regular setback of spontaneous succession towards forest.     

Local translation in neuronal compartments: how local is local?

Efficient neuronal function depends on the continued modulation of the local neuronal proteome. Local protein synthesis plays a central role in tuning the neuronal proteome at specific neuronal regions. Various aspects of translation such as the localization of translational machinery, spatial spread of the newly translated proteins, and their site of action are carried out in specialized neuronal subcompartments to result in a localized functional outcome. In this review, we focus on the various aspects of these local translation compartments such as size, biochemical and organelle composition, structural boundaries, and temporal dynamics. We also discuss the apparent absence of definitive components of translation in these local compartments and the emerging state‐of‐the‐art tools that could help dissecting these conundrums in greater detail in the future.     

The genomics of local adaptation in trees: are we out of the woods yet?

There is substantial interest in uncovering the genetic basis of the traits underlying adaptive responses in tree species, as this information will ultimately aid conservation and industrial endeavors across populations, generations, and environments. Fundamentally, the characterization of such genetic bases is within the context of a genetic architecture, which describes the mutlidimensional relationship between genotype and phenotype through the identification of causative variants, their relative location within a genome, expression, pleiotropic effect, environmental influence, and degree of dominance, epistasis, and additivity. Here, we review theory related to polygenic local adaptation and contextualize these expectations with methods often used to uncover the genetic basis of traits important to tree conservation and industry. A broad literature survey suggests that most tree traits generally exhibit considerable heritability, that underlying quantitative genetic variation (Q_ST) is structured more so across populations than neutral expectations (F_ST) in 69% of comparisons across the literature, and that single-locus associations often exhibit small estimated per-locus effects. Together, these results suggest differential selection across populations often acts on tree phenotypes underlain by polygenic architectures consisting of numerous small to moderate effect loci. Using this synthesis, we highlight the limits of using solely single-locus approaches to describe underlying genetic architectures and close by addressing hurdles and promising alternatives towards such goals, remark upon the current state of tree genomics, and identify future directions for this field. Importantly, we argue, the success of future endeavors should not be predicated on the shortcomings of past studies and will instead be dependent upon the application of theory to empiricism, standardized reporting, centralized open-access databases, and continual input and review of the community’s research.     

Are local patterns of anthropoid primate diversity related to patterns of diversity at a larger scale?

Aims (1) To determine the relationship between local and regional anthropoid primate species richness. (2) To establish the spatial and temporal scale at which the ultimate processes influencing patterns of primate species coexistence operate. Location Continental landmasses of Africa, South America and Asia (India to China, and all islands as far south as New Guinea). Methods The local–regional species richness relationship for anthropoid primates is estimated by regressing local richness against regional richness (independent variable). Local richness is estimated in small, replicate local assemblages sampled in regions that vary in total species richness. A strong linear relationship is taken as evidence that local assemblages are unsaturated and local richness results from proportional sampling of the regional pool. An asymptotic curvilinear relationship is interpreted to reflect saturated communities, where strong biotic interactions limit local richness and local processes structure the species assemblage. As a further test of the assumption of local assemblage saturation, we looked for density compensation in high‐density local primate assemblages. Results The local–regional species richness relationship was linear for Africa and South America, and the slope of the relationship did not differ between the two continents. For Asia, curvilinearity best described the relationship between local and regional richness. Asian primate assemblages appear to be saturated and this is confirmed by density compensation among Asian primates. However, density compensation was also observed among African primates. The apparent assemblage saturation in Asia is not a species–area phenomenon related to the small size of the isolated islands and their forest blocks, since similar low local species richness occurs in large forests on mainland and/or peninsular Asia. Main conclusions In Africa and South America local primate assemblage composition appears to reflect the influence of biogeographic processes operating on regional spatial scales and historical time scales. In Asia the composition of primate assemblages are by‐and‐large subject to ecological constraint operating over a relatively small spatial and temporal scale. The possible local influence of the El Niño Southern Oscillations on the evolution and selection of life‐history characteristics among Asian primates, and in determining local patterns of primate species coexistence, warrants closer inspection.     

Study of local hydrodynamic environment in cell-substrate adhesion using side-view μPIV technology

Tumor cell adhesion to the endothelium under shear flow conditions is a critical step that results in circulation-mediated tumor metastasis. This study presents experimental and computational techniques for studying the local hydrodynamic environment around adherent cells and how local shear conditions affect cell-cell interactions on the endothelium in tumor cell adhesion. To study the local hydrodynamic profile around heterotypic adherent cells, a side-view flow chamber assay coupled with micro particle imaging velocimetry (μPIV) technique was developed, where interactions between leukocytes and tumor cells in the near-endothelial wall region and the local shear flow environment were characterized. Computational fluid dynamics (CFD) simulations were also used to obtain quantitative flow properties around those adherent cells. Results showed that cell dimension and relative cell-cell positions had strong influence on local shear rates. The velocity profile above leukocytes and tumor cells displayed very different patterns. Larger cell deformations led to less disturbance to the flow. Local shear rates above smaller cells were observed to be more affected by relative positions between two cells.     

Mechanism of adenylate kinase. Is there a relationship between local substrate dynamics, local binding energy, and the catalytic mechanism?

Adenylyl (beta,gamma-methylene)diphosphonic acid (AMPPCP) labeled with deuterium at the adenine ring ([8-2H]AMPPCP) and at the beta,gamma-methylene group (AMPPCD2P), as well as adenosine 5'-monophosphate labeled at the adenine ring ([8-2H]AMP), was synthesized and used for deuterium nuclear magnetic resonance (NMR) determination of effective correlation times (tau c) of the free nucleotide and the complexes with adenylate kinase (AK). Extensive and rigorous control experiments and theoretical analysis were performed to justify the validity of the experimental approaches, particularly the fast exchange condition, and the reliability of the tau c values obtained. For the free nucleotide, the results suggest that the phosphonate group of free AMPPCP possesses appreciable local mobility relative to the adenine ring and that complexation with Mg2+ greatly reduced such a local mobility. For the complexes with AK, effective tau c values of 7, 15, 28, 28, and 27 ns were obtained for AMPPCD2P, MgAMPPCD2P, [8-2H]AMPPCP, Mg[8-2H]AMPPCP, and [8-2H]AMP, respectively. These results suggest that the adenine ring of substrates is rigidly bound in all cases, that the phosphonate chain of AMPPCP possesses considerable local mobility, and that Mg2+ reduces such local mobility but does not totally immobilize it. The local dynamics of the analogues bound to AK was correlated with local binding energies for the binding of MgAMPPCP and MgATP to AK estimated from the binding studies by proton NMR and other techniques, in conjunction with the binding theory of Jencks [Jencks, W. P. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 4046-4050]. The results suggest that no general correlation exists between the local rigidity of portions of a bound substrate and the corresponding (ground state) local binding energy contributed by these portions. In particular, the adenosine moiety contributes little to the binding energy despite the fact that the adenine ring is rigidly bound; the triphosphate (PPPi) moiety behaves oppositely; Mg2+ immobilizes the triphosphate chain but does not enhance binding. Finally, isomers of the substitution-inert beta,gamma-bidentate Cr(III) complexes of adenosine 5'-triphosphate (CrATP) were used to probe two unresolved catalytic problems implicitly related to the local mobility of the phosphonate chain of AMPPCP in the AK-MgAMPPCP complex. The first problem concerns the result of electron paramagnetic resonance (EPR) studies that (Rp)- but not (Sp)-[beta-17O]ATP caused a line broadening in the Mn(II) EPR spectrum of the AK-MnATP complex [Kalbitzer, H. R., Marquetant, R., Connolly, B. A., & Goody, R. S. (1983) Eur. J. Biochem. 133, 221-227].(ABSTRACT TRUNCATED AT 400 WORDS)     

What determines attitude of local people towards tiger and leopard in Nepal?

Understanding attitude of local people towards big cats is vital for conservation interventions to succeed. Taking tigers and leopards as focal species, we investigated local peoples' attitude towards four subjects—tiger, tiger conservation, leopard, and leopard conservation—considering demographic and socio-economic factors as well as past experience with such predators in Nepal's first national park and a world heritage site, Chitwan National Park. The data were collected from 414 local people using structured questionnaires and their attitude towards the four subjects determined. We performed ordinal logistic regression analysis to identify the best fitted model and significant variables affecting attitudes. While majority of the people (51%) strongly liked tigers, fewer people (38%) had similar view while it came to leopard. However, a greater proportion of people strongly agreed that the conservation of tigers (61%) and leopards (53%) is important. About 12% people had negative attitude towards both big cats. We found women and low income respondents to likely have negative attitudes and higher caste Hindus to have positive attitudes towards both big cats and their conservation. Better educated persons and the owners to larger herds of livestock only agreed on conservation of tiger but not leopard. Past experience with the predator negatively affected attitude towards tiger but not leopard. We suggest the identified cohort of people with negative attitudes be more targeted in conservation initiatives. The reasons behind the similarities and differences in peoples’ attitudes are discussed and designation of species-specific programmes for both cats is recommended.     

Can local energy minimization refine the PDB structures of different resolution universally?

Local energy minimization was statistically tested as the refinement strategy for PDB structure pairs of different resolution. The 13 pairs of structures with the only difference being the resolution were extracted from PDB and represented structures of 11 identical proteins obtained with different x-ray diffraction techniques. The rmsd distribution was calculated for these pairs before and after local energy minimization of each structure. MMFF94 was used for energy calculations and the quasi-Newtonian method was used for local energy minimization. By comparison of these two rmsd distributions, the local energy minimization was proved to statistically increase the structural differences in pairs, so it cannot be used for refinement purposes. To explore the prospects of complex refinement strategies based on energy minimization, randomized structures were obtained by moving the initial PDB structures as far as the minimized structures had been moved in the multidimensional space of atomic coordinates. For these randomized structures the rmsd distribution was calculated and compared with the one for minimized structures. The significant differences in their mean values proved the energy surface of the protein to have only few minima near the conformations of different resolution obtained by x-ray analysis for PDB. Some other results we obtained exploring the energy surface near these conformations are also presented. These results are expected to be useful for the development of new protein refinement strategies based on energy minimization.     

Do local communities support the conservation of endangered Przewalski’s gazelle?

Understanding local attitudes and opinion is vital to the success of conservation programs, especially in areas of expanding human populations such as China. Przewalski’s gazelle (Procapra przewalskii) is an endangered ungulate found only in the eastern part of the Qinghai-Tibet Plateau. The gazelle is a conservation focus; however, little is known regarding how this animal is perceived by local people. To understand the relationship between demography, levels of conservation knowledge, and attitudes, we conducted 174 interviewer-led surveys in villages located inside, near, and away from the gazelle’s home ranges around Qinghai Lake, China. About half of the interviewees were aware of gazelle conservation. No more than half of the interviewees were aware that grassland fence, livestock, roads, and wolves negatively impact upon gazelle. On the whole, the majority of interviewees supported the conservation of gazelle. There were high levels of support for both establishing a special protected area and investing more funds in conservation but very few interviewees reported personal benefits from gazelle conservation. Overall attitude of interviewees toward the gazelle differed significantly among regions and people living near the range of gazelle were the most positive. Interviewees with conservation information were more positive than interviewees lacking such information. People who had more education or possessed more grassland had more positive attitudes toward the gazelle. This study suggests that greater communication is needed with local people. Programs that promote public engagement and participation are required for the conservation of Przewalski’s gazelle and other larger herbivores on the Qinghai-Tibet Plateau.     

Global versus local extinction in a network model of plant–pollinator communities

The loss of a species from an ecological community can trigger a cascade of additional extinctions; the complex interactions that comprise ecological communities make the dynamics and impacts of such a cascade challenging to predict. Previous studies have typically considered global extinctions, where a species cannot re-enter a community once it is lost. However, in some cases a species only becomes locally extinct, and may be able to reinvade from surrounding communities. Here, we use a dynamic, Boolean network model of plant–pollinator community assembly to analyze the differences between global and local extinction events in mutualistic communities. As expected, we find that compared to global extinctions, communities respond to local extinctions with lower biodiversity loss, and less variation in topological network properties. We demonstrate that in the face of global extinctions, larger communities suffer greater biodiversity loss than smaller communities when similar proportions of species are lost. Conversely, smaller communities suffer greater loss in the face of local extinctions. We show that targeting species with the most interacting partners causes more biodiversity loss than random extinctions in the case of global, but not local, extinctions. These results extend our understanding of how mutualistic communities respond to species loss, with implications for community management and conservation efforts.     

Do local abundances of British birds change with proximity to range edge?

Aim Species generally vary in the density they attain at different sites, prompting the question of whether this variation is systematic across their range. We investigate this question using data on the abundance and distribution of thirty-two species of passerine birds across Britain derived from censuses organized by the British Trust for Ornithology. Methods Analysis is complicated by the issue of quantifying the distance of any particular census location from the edge of the range of a species when the study area encompasses only part of its entire distribution. No measure of this quantity is a priori the correct one, and so we use a variety of different measures which make differing assumptions about how abundances might be structured across species ranges. Results None of the measures used reveal any consistent relationships between the density attained by species at census sites and the spatial positions of those sites. Only thirteen species show significant relationships with any of the measures, and no more than seven species with any single measure. Main conclusion In summary, there is no convincing evidence that passerine bird densities are usually lower towards range edges in Britain. We discuss possible reasons for these findings.     

All signaling is local?

The mechanism of signal transmission following ligand stimulation of receptor tyrosine kinases in living cells is poorly understood. Recent studies have visualized the spatio-temporal pattern of EGF signaling, indicating that receptor density is an important factor in the mechanism of lateral propagation of local EGF signaling.     

A model for the perception of curves in dot figures: The role of local salience of “virtual lines”

In many models of visual information processing the notion of a virtual line or dipole is introduced in order to represent the configurational information, notably length and relative orientation, between identical figure elements in figures with discrete elements. Virtual lines have proven to be very useful in predicting perceptual phenomena (Julesz et al. 1973; Stevens 1978). In the present study, virtual lines are utilized in a model which aims to predict the perception of (dotted) curves in dot figures. Clearly many possible curves, formed by adjacent virtual lines, can be constructed within a set of dots. It is proposed that already at the local level of the virtual lines each line has a perceptual salience which results from the function induced by the global dot figure. It is this local line salience or connectivity that directs further processing and determines the curves to be seen in a dot figure. The model presented is an information processing model with a clear modular design. It entails three successive levels of representation. First image functions are derived through a convolution of the input with gaussian distribution functions. Next, a discrete internal representation is extracted from the image function consisting of two primitives; blobs, representing the dots, and virtual lines, representing pairwise relations between blobs. The attributes of the blobs are their positions in the image plane, while those of the virtual lines are length, relative orientation and connectivity. At the third level, the discrete internal representation is used to predict the perceived curves. It is shown that the model has advantages over other approaches, e.g. autocorrelation and network models.