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PubMed2006

[Three-dimensional spatial distribution patterns of Monochamus alternatus and its natural enemy Dastarcus helophoroides].

In 2003 to approximately 2005, the Monochamus alternatus-infected Pinus thunbergii, P. massoniana and P. elliotii in pure and mixed forests were selected as attractants and dissected with one meter section manner, and five aggregation indices were used to analyze the spatial distribution patterns of M. alternatus and its natural enemy Dastarcus helophoroides. The results showed that M. alternatus and D. helophoroides had the horizontal distribution indices of diffused coefficient C > 1, diffused index I delta > 1, Kuno index C(A) > 0, clump intensity index I > 1, and swarm index Iw > 1 in the two stands, suggesting their aggregated horizontal distribution patterns, and except D. helophoroides on the P. massoniana in mixed forest appeared assemble vertical distribution, these two insects all had an even vertical distribution, with their C < 1, I delta < 1, C(A) < 0, Iw < 1, and I < 0. The spatial distribution patterns of M. alternatus and D. helophoroides were consistent, and the latter was spatially following the former.

Animals↗
PubMed1998

Upper displacement limits for spatially broadband patterns containing bandpass noise.

How is the spatial-frequency content of a moving broadband pattern analysed by the visual system? Observers were asked to discriminate the direction of motion in random-noise patterns containing equal energy in each two-dimensional octave band. Uncorrelated noise could be introduced into either low- or high-frequency bands in order to force the visual system to rely on the outputs of putative mechanisms tuned to a narrow frequency range of the stimulus. In two experiments the dependent measure was the magnitude of dmax, the largest discrete displacement whose direction could be discriminated reliably. It was found that dmax was unaffected by the presence of high-frequency noise reaching down to 0.67 c/deg, but that the task became impossible thereafter. In the case of low-frequency noise, dmax fell as the noise was moved up towards about 2 c/deg, at which point the task became impossible at any displacement. This pattern of results would be expected if the system were using information from the lowest signal frequencies in all conditions. In experiment 2, dmax was measured for stimuli in which the spectral position and quantity of high-frequency noise were manipulated. It was found that only noise spectrally-adjacent to the signal band has a detrimental effect on dmax. Three different single-filter models of motion detection each failed to provide a satisfactory account of the spatial-frequency range of good direction discrimination performance. Rather, the modelling shows that the visual system can access the outputs of a low-frequency channel when the noise is high and a high-frequency channel when the noise is low.

Contrast Sensitivity↗
PubMed2005

Wind-dispersed seed deposition patterns and seedling recruitment of Artemisia halodendron in a moving sandy land.

BACKGROUND AND AIMS: Artemisia halodendron is a native sub-shrub that occurs mainly in moving and semi-fixed sandy lands in Inner Mongolia, China. Information on the spatial patterns of wind-dispersed seed deposition and seedling recruitment of A. halodendron inhabiting moving sandy lands is very limited. The aim of this study was to examine wind-dispersed seed deposition patterns and post-dispersal recruitment of A. halodendron seedlings. * METHODS: The spatial patterns of wind-dispersed seed deposition and seedling recruitment of A. halodendron were examined by investigating the numbers of deposited seeds, emerged and surviving seedlings using sampling points at a range of distances from the parent plant in eight compass directions for two consecutive growing seasons. * KEY RESULTS: Wind-dispersed seed deposition showed considerable variation between directions and years. Wind transported A. halodendron seeds only a few meters away from the parent plant in all eight directions. Seedling emergence and establishment also showed between-direction and between-year variability, but the spatial pattern of seedling distribution differed from that of seed deposition. Only a very small fraction (<1 %) of the deposited seeds emerged in the field and survived for long enough to be included in our seedling censuses at the end of the growing season. * CONCLUSIONS: The spatial variation in wind speed and frequency strongly affects the pattern of seed deposition, although the variation in seed deposition does not determine the spatial pattern of seedling recruitment. Seeds of A. halodendron are not dispersed very well by wind. The low probability of recruitment success for A. halodendron seedlings suggests that this species does not rely on seedling recruitment for its persistence and maintenance of population.

Artemisia↗
PubMed2005

Single-neuron theory of consciousness.

By most accounts, the mind arises from the integrated activity of large populations of neurons distributed across multiple brain regions. A contrasting model is presented in the present paper that places the mind/brain interface not at the whole brain level but at the level of single neurons. Specifically, it is proposed that each neuron in the nervous system is independently conscious, with conscious content corresponding to the spatial pattern of a portion of that neuron's dendritic electrical activity. For most neurons, such as those in the hypothalamus or posterior sensory cortices, the conscious activity would be assumed to be simple and unable to directly affect the organism's macroscopic conscious behavior. For a subpopulation of layer 5 pyramidal neurons in the lateral prefrontal cortices, however, an arrangement is proposed to be present such that, at any given moment: (i) the spatial pattern of electrical activity in a portion of the dendritic tree of each neuron in the subpopulation individually manifests a complexity and diversity sufficient to account for the complexity and diversity of conscious experience; (ii) the dendritic trees of the neurons in the subpopulation all contain similar spatial electrical patterns; (iii) the spatial electrical pattern in the dendritic tree of each neuron interacts non-linearly with the remaining ambient dendritic electrical activity to determine the neuron's overall axonal response; (iv) the dendritic spatial pattern is reexpressed at the population level by the spatial pattern exhibited by a synchronously firing subgroup of the conscious neurons, thereby providing a mechanism by which conscious activity at the neuronal level can influence overall behavior. The resulting scheme is one in which conscious behavior appears to be the product of a single macroscopic mind, but is actually the integrated output of a chorus of minds, each associated with a different neuron.

Animals↗
PubMed2001

Spatiotemporal dynamics of Floerkea proserpinacoides (Limnanthaceae), an annual plant of the deciduous forest of eastern North America.

Because environmental filters are temporally and spatially heterogeneous, there often is a lack of significant relationship between the spatial patterns of successive life stages in plant populations. In this study, we determined the spatiotemporal relationships between different life stages in two populations of an annual plant of the deciduous forests of eastern North America, Floerkea proserpinacoides. Demographic surveys were done over a 4-yr period, and experiments were performed in the field and under controlled conditions to test for the effects of various environmental factors on population dynamics. There was a general lack of relationship between the spatial patterns of seed bank and seedling density, and a lack of similarity between their spatial correlograms. This was related mostly to the effects of spatially variable environmental filters operating on germination and emergence. However, environmental filters acting on plant survival were stable through time and contributed to stabilize the density and spatial patterns of the populations. Despite density-dependent presenescence mortality, spatial patterns of seedlings and mature individuals were similar and their correlograms were alike, suggesting that mortality did not fully compensate for density. Estimated fecundity was negatively correlated with population density over the study period. Although flower production started only 2-3 wk after emergence, seed maturation mostly occurred at the end of the life cycle, just before the onset of plant senescence. Yet, individual fecundity was low for an annual plant, i.e., 3.0 ± 0.5 mature seeds/plant (mean ± 1 SE). Seed predation by vertebrates was not significant. Low soil moisture had little effect on the total number of seeds germinating, although it slowed down the germination process. In quadrats where leaf litter was experimentally doubled, seedling emergence was lower than in control quadrats; in quadrats where leaf litter was completely removed, emergence did not differ from that in control quadrats. Susceptibility to drought stress was higher for seedlings than for mature plants. Although the species does not maintain a long-term persistent soil seed bank, other factors, such as density-dependent fecundity and autogamy, may temper population fluctuations through time and reduce the probability of local extinction.

Journal Article↗
PubMed1996

The orientation of the bi-leaflet CarboMedics valve in the mitral position determines left ventricular spatial flow patterns.

OBJECTIVES: In the mitral annulus bi-leaflet mechanical valves can be oriented in two ways: the anatomical orientation with the hinge line parallel to a line through the commissures of the native valve (90 degrees). The influence of this orientation on the left ventricular spatial flow pattern and valve leaflet opening was investigated in pigs. METHODS: In 9 pigs a CarboMedics mitral valve prosthesis was implanted in the ) degree position and in 9 pigs in the 90 degree orientation. Two dimensional echocardiographic and color Doppler recordings were performed before surgery, immediately after surgery and after 6 weeks. RESULTS: In the native valve the diastolic flow pattern was characterized by a central inflow and backflow away from the apex along the left ventricular wall. In the 0 degree orientation a diastolic flow pattern with an asymmetrical inflow was observed, resulting from a greater extension of the jet along the lateral wall compared to the jet along the interventricular septum. Mid-diastolic back-flow away from the left ventricular apex was directed towards the valve prosthesis. In the 2-dimensional echocardiographic recordings the opening angle of both prosthetic leaflets was different showing a larger opening angle of the posterior leaflet. In the 90 degree orientation a diastolic flow pattern with paradoxical flow directions was recorded, that could only be explained in a 3-dimensional way: one inflow jet along the anterior wall, one inflow jet along the posterior wall and back-flow away from the apex sandwiched in between the two inflow jets. In this orientation the 2-dimensional echocardiographic recordings showed symmetrical opening of the two leaflets of the prosthesis. CONCLUSIONS: The orientation of the CarboMedics bi-leaflet mechanical valve prosthesis in the mitral valve annulus determines the left ventricular spatial flow pattern. The flow pattern resulting from the 0 degree orientation, was associated with asymmetrical leaflet motion, while the 90 degree orientation flow pattern was associated with symmetrical leaflet motion. These findings may be of importance for prosthetic valve function as well as for left ventricular kinetics.

Animals↗
PubMed1999

A Caenorhabditis elegans wee1 homolog is expressed in a temporally and spatially restricted pattern during embryonic development.

A wee1 homolog, wee-1.1, is expressed in both a temporally and spatially restricted pattern during early Caenorhabditis elegans embryogenesis, and is undetectable throughout the remainder of embryogenesis. The wee-1.1 message appears to be zygotically expressed in the somatic founder cell E of the 12-cell embryo. This expression disappears when the E blastomere divides for the first time. The wee-1.1 message then appears transiently in the nuclei of the eight great-granddaughter cells of the AB somatic founder cell, just before these cells divide in the 16-cell embryo. Following this division, the wee-1.1 mRNA is no longer detectable throughout the remainder of embryogenesis. The expression of wee-1.1 in the E blastomere and in the AB progeny appears to be restricted to nuclei in prophase and metaphase of the cell cycle. Analysis of the wee-1.1 mRNA expression pattern in maternal-effect lethal mutants suggests that this expression pattern is restricted to cells of the E and AB fates in the early embryo. This mRNA expression pattern is restricted to a 10-15-min span of embryonic development and may be regulating the timing of crucial cell divisions at this early stage of development.

Amino Acid Sequence↗
PubMed2004

[Biodiversity of tree species, their populations' spatial distribution pattern and interspecific association in mixed deciduous broadleaved forest in Changbai Mountains].

Based on the data collected from the sampling plot with an area of 1 hm2 at the Experimental and Management Bureau of Jiaohe in Jilin Province, this paper analyzed and researched the community structure, biological diversity, spatial distribution pattern and interspecific association between tree species populations in a mixed deciduous broadleaved forest. The results indicated that there was no obvious dominant order among tree species populations, and the indices of tree species diversity such as Shannon-Wiener index (H'), Pielou evenness index (E) and Simpson ecological dominant index (D) were all low. Shrub and herb species diversity indices were also not high. The spatial distribution pattern of five dominant tree species all presented aggregative. Based on 2 x 2 contigency table, the interspecific associations of 15 tree species in the community were examined by means of chi2-test, together with the association coefficient (AC). The results showed that there were 14 species pairs in 15 species showing significantly negative association. The proportion of species pairs showing negative association was much more than that of showing positive association. It could be deduced that the community was instable and at the stage of autogenic succession from soft deciduous broadleaved forest to hard deciduous broadleaved forest, and then, the Korean pine broadleaved forest.

Biodiversity↗
PubMed1980

Sex differences in pattern copying: spatial cues or motor skills?

Accuracy of pattern copying was studied in male and female 10-year-olds. It was hypothesized that previous research reporting male superiority on this measure may have actually reflected the gross-motor skills requirements of the task. The use of smaller stimuli was predicted to eliminate or reverse this sex difference. In addition, visual reference cues were included on some trials to examine their potential facilitation effects. Contrary to expectations, males benefited from spatial reference cues whereas females did not, independent of stimulus size.

Child↗
PubMed2005

Origin, structure, and role of background EEG activity. Part 3. Neural frame classification.

OBJECTIVE: To show that cortical responses to conditioned stimuli (CS) include intermittently induced spatial patterns of amplitude modulation (AM) of beta-gamma oscillation called frames. METHODS: EEGs were recorded from 8x8 high-density arrays fixed on primary sensory cortices of rabbits trained to discriminate CS with reinforcement (CS+) from those without (CS-). EEG frames were located with a pragmatic information index, H(e). The spatial patterns of the first 3 frames on each of 37-40 trials were measured by the square of 64 analytic amplitudes from the Hilbert transform to give points in 64-space. The questions were asked: Did the frames from CS+ trials and CS- trials differ within each sequential group? Did the 3 frames differ from each other (form 3 clusters of points)? RESULTS: EEG frames that were identified by high H(e) had AM patterns that could be classified with respect to CS+ and CS- well above chance levels. Two stages of correct frame classification occurred on each trial: 40-130 ms after CS onset with a gamma carrier frequency, and 450-550 ms with a beta carrier frequency. Peak power in the beta frames was double that in gamma frames, and mean pattern surface area of beta frames was nearly 4-fold greater. CONCLUSIONS: Under the impact of a CS on a sensory neocortex, the background EEG activity reorganized in sequential frames of coordinated activity, first local and modality-specific, thereafter global. SIGNIFICANCE: The size, texture and duration of these AM patterns indicate that spatial patterns of human beta frames may be accessible with high-density scalp arrays for correlation with phenomenological reports by human subjects.

Acoustic Stimulation↗
PubMed2000

Neuronal activity in macaque supplementary eye field during planning of saccades in response to pattern and spatial cues.

The aim of this study was to determine whether neuronal activity in the macaque supplementary eye field (SEF) is influenced by the rule used for saccadic target selection. Two monkeys were trained to perform a variant of the memory-guided saccade task in which any of four visible dots (rightward, upward, leftward, and downward) could be the target. On each trial, the cue identifying the target was either a spot flashed in superimposition on the target (spatial condition) or a foveally presented digitized image associated with the target (pattern condition). Trials conforming to the two conditions were interleaved randomly. On recording from 439 SEF neurons, we found that two aspects of neuronal activity were influenced by the nature of the cue. 1) Activity reflecting the direction of the impending response developed more rapidly following spatial than following pattern cues. 2) Activity throughout the delay period tended to be higher following pattern than following spatial cues. We consider these findings in relation to the possible involvement of the SEF in processes underlying attention, arousal, response-selection, and motor preparation.

Analysis of Variance↗
PubMed2000

Sinorhizobium meliloti nfe (nodulation formation efficiency) genes exhibit temporal and spatial expression patterns similar to those of genes involved in symbiotic nitrogen fixation.

The nfe genes (nfeA, nfeB, and nfeD) are involved in the nodulation efficiency and competitiveness of the Sinorhizobium meliloti strain GR4 on alfalfa roots. The nfeA and nfeB genes are preceded by functional nif consensus sequences and NifA binding motifs. Here, we determined the temporal and spatial expression patterns of the nfe genes in symbiosis with alfalfa. Translational fusions of the nfe promoters with the gusA gene and reverse transcription-polymerase chain reaction analyses indicate that they are expressed and translated within mature nitrogen-fixing nodules and not during early steps of nodule development. Within the nodules the three nfe genes exhibit a spatial expression pattern similar to that of genes involved in symbiotic nitrogen fixation. We show that nfeB and nfeD genes are expressed not only from their own promoters but also from the upstream nfe promoter sequences. Furthermore, with the use of specific antibodies the NfeB and NfeD proteins were detected within the root nodule bacteroid fraction. Finally, NfeB was inmunolocalized in the bacteroid cell membrane whereas NfeD was detected in the bacteroid cytoplasm.

Bacterial Proteins↗
PubMed2006

Local environmental effects and spatial effects in macroecological studies using mapped abundance classes: the case of the rook Corvus frugilegus in Scotland.

1. The study of the spatial pattern of species abundance is complicated by statistical problems, such as spatial autocorrelation of the abundance data, which lead to the confusion of environmental effects and dispersal. 2. Atlas-derived data for the rook in Scotland are used as a case study to propose an approach for assessing the likely contribution of dispersal and local environmental effects, based on a Bayesian Conditional Autoregressive (CAR) approach. 3. The availability of moist grasslands is a key factor explaining the spatial pattern of abundance. This is influenced by a combination of climatic and soil-related factors. A direct link to soil properties is for the first time reported for the wide-scale distribution of a bird species. In addition, for this species, dispersal seems to contribute significantly to the spatial pattern and produces a smoother than expected decline in abundance at the north-western edge of its distribution range. Areas where dispersal is most likely to be important are highlighted. 4. The approach described can help ecologists make more efficient use of atlas data for the investigation of the structure of species abundance, and can highlight potential sink areas at the landscape and regional scale. 5. Bayesian spatial models can deal with data autocorrelation in atlas-type data, while clearly communicating uncertainty through the estimation of the full posterior probability distribution of all parameters.

Animals↗
PubMed1985

Spatial EEG patterns, non-linear dynamics and perception: the neo-Sherringtonian view.

Spatial analysis with preamplifier arrays and computers offers fresh perspectives on brain function. Realization of its potential depends on development of appropriate procedures for data processing and display, experimental paradigms to serve as benchmarks, and theories of brain function to predict what to look for and how to distinguish valid results from artifacts. Measurement of EEGs from arrays of 64 electrodes chronically implanted on the olfactory bulbs of rabbits that are trained to discriminate odorant conditioned stimuli show that the odorants induce spatially distinctive amplitude patterns of neural activity. The odor-specific information density is inferred to be uniform over the whole main bulb. The neural dynamics that produce these activity patterns emerge from the synaptically interactive sheet of excitatory mitral and inhibitory granule cells with distributed input and output tracts and with static nonlinearities deriving from the nerve impulse mechanism. Excitatory synapses between mitral cells are subject to modification when odorants are paired with unconditioned stimuli, thus forming nerve cell assemblies. Odorant-specific information established by a stimulus locally in the bulbar unit activity is integrated with past experience by an assembly, disseminated over the entire bulb on the order of 100 mm2 in area in a time period of 2.5 ms, and sustained for a time period on the order of 0.1 s. An arbitrary spatial sample on the order of 20% of bulbar EEG activity captures the entire integrated information albeit at lesser resolution than the whole. This synaptic mechanism of local input and global output may be common to all of the cerebral cortex. The implications are discussed for neocortical sensory systems, motor pattern generators, and goal-directed behavior in the context of self-organizing non-linear dynamic systems.

Aging↗
PubMed1996

Event-related potentials reveal topographical and temporal distinct neuronal activation patterns for spatial and object working memory.

This study examined whether working memory processes for object and spatial information are associated with different patterns of ERP activity. Subjects performed two versions of a delayed match-to-sample task in which either object forms or two-dimensional spatial configurations (S1) had to be encoded and retained in working memory for 6800 ms for comparison with a subsequent stimulus (S2). Event-related potentials (ERPs) were recorded from 29 electrode sites in the S1-S2 interval. Negative slow wave activity in the ERP varied with both, the type of memory task and the amount of materials held in working memory. When spatial information was maintained in working memory negative slow wave activity rapidly rose at recording sites overlying posterior parietal and occipital cortical areas. At these recording sites, slow wave increased in amplitude with increasing spatial memory load. For object information, load-sensitive negative slow wave activity was obtained approximately 2000 ms later than in the spatial task and it was focused to mid-frontal recording sites. Moreover, in the object memory task more pronounced negative slow wave activity was found at right inferior temporal recording sites indicating a larger involvement of the right temporal lobe in the processing of object as compared to spatial information. The results provide evidence for the notion that encoding and retention processes for object information and for spatial information can be functionally dissociated and involve differential patterns of neuronal activation rapidly shifting in time.

Adult↗
PubMed2003

[Structures and spatial distribution patterns of dominant populations in Sycopsis sinensis community in Houhe Nature Reserve].

Based on the investigation data of 2 quadrats (1,600 m2 and 2,400 m2) in Houhe Nature Reserve, tree size class method was applied to analyze the structures of the dominant populations, and t-test of v/m ratio, mean crowing index, negative binomial parameter, patchiness index and Morisita index were applied to analyze the spatial distribution patterns of two dominant populations. The clumping degrees were also evaluated according to their size classes in different quadrats. The results showed that Sycopsis sinensis population was a declining population, dominated by IV trees and difficult to regenerate. In the population, the individual percentage of IV trees accounted for 79.4% in Q1 and 87.4% in Q2, and those of I trees and II trees were few. However, the population of Cyclobalanopsis axyodon was an growing one, and the individual percentages declined with the increasing size classes. The spatial distribution patterns of the two dominant populations distributed in clumps, but the clumping degrees existed diversity. With the increase of the size classes, the clumping degree of the population of Sycopsis sinensis intensified from random to clumping distribution, while that of the population of Cyclobalanopsis axyodon weakened from clumping to random distribution.

Conservation of Natural Resources↗
PubMed1999

Changing patterns of spatial buffering of glutamate in developing rat retinae are mediated by the Müller cell glutamate transporter GLAST.

The patterns of expression of the glutamate transporter GLAST were compared with the patterns of uptake of exogenous D-aspartate, which is a substrate for all glutamate transporters. At postnatal day 0, fine radial processes and end feet of presumptive Müller cells were weakly immunoreactive for GLAST. At postnatal day 3, intense labelling was associated with astrocytes enveloping newly formed blood vessels on the vitread surface of the retina. Between postnatal days 7 and 10, there was a rapid increase in the intensity of labelling in the Müller cells but clear stratification of GLAST-immunoreactive processes in the inner plexiform layer was not observed until postnatal day 14. By comparison, D-aspartate uptake was initially associated with a wide variety of cellular elements including most neuroblasts, presumptive Müller cells, and astrocytes associated with blood vessels but was absent from the somata of many neurons in the ganglion cell layer and amacrine cell layer. There was a gradual contraction in the numbers of cells that were able to take up D-aspartate, such that, by adulthood, uptake was restricted mainly to Müller cells and astrocytes. We conclude that, during early retinal development, the low levels of GLAST expression by Müller cells permit D-aspartate, and by inference, glutamate, to permeate the retina freely, thus allowing uptake by other glutamate transporters on other cell types. As the retina matures, increased expression of GLAST by Müller cells restricts the access of D-aspartate to other cellular compartments in the retina. This changing pattern of spatial buffering of glutamate by GLAST probably has significant implications regarding our understanding of the role of glutamate during processes such as retinal synaptogenesis.

ATP-Binding Cassette Transporters↗
PubMed1987

Single fiber mapping of spatial excitation patterns in the electrically stimulated auditory nerve.

Spatial maps of electrical excitation were constructed by comparing electrical threshold with acoustic CF for large populations of auditory nerve fibers in cats. Thresholds among fibers with the same CF varied by factors of 4 or more. Monopolar electrodes, both intracochlear and extracochlear, excited fibers throughout the cochlea without spatial selectivity. Stimulation with intracochlear bipolar electrodes produced a minimum in the threshold distribution adjacent to the electrodes. With longitudinally oriented pairs, the width, depth, and location of the minimum shifted with stimulus polarity; spread of excitation throughout the cochlea occurred with stimulus intensities 6.2 to 14 dB above the lowest threshold. With radially oriented pairs, minima were sharper and deeper; spread of excitation occurred at intensities 23.7 to 32.8 dB above the minimum threshold.

Acoustic Stimulation↗