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PubMed1986

Respiratory-phase-related coding of olfactory information in the olfactory bulb of awake freely-breathing rabbits.

The "across-neuron pattern" theory of olfactory information coding states that odorants are represented by spatial patterns of activity produced across-neurons in the olfactory bulbs. The present study analyzes the different response patterns encoding olfactory information in both the inspiratory and expiratory phases of the respiratory cycles of awake freely-breathing rabbits. We recorded the single-unit responses of 31 neurons to 5 different odorants, 3 of which were repeatedly delivered 5 times each. These responses were characterized by the change in their mean firing activity during the inspiratory and expiratory phases of the respiratory cycles respectively. Their processing using principal component analyses revealed that both the inspiration- and the expiration-related across-neuron profiles of responses contained information appropriate to the specification of each odorant. It was therefore concluded that there was a dynamic representation of odorants in the olfactory bulb of awake freely-breathing animals. This alternate representation of odorants by two profiles and its physiological significance are discussed.

Acetophenones↗
PubMed2006

Small-world network organization of functional connectivity of EEG slow-wave activity during sleep.

OBJECTIVE: To analyze the functional connectivity patterns of the EEG slow-wave activity during the different sleep stages and Cyclic Alternating Pattern (CAP) conditions, using concepts derived from Graph Theory. METHODS: We evaluated spatial patterns of EEG slow-wave synchronization between all possible pairs of electrodes (19) placed over the scalp of 10 sleeping healthy young normal subjects using two graph theoretical measures: the clustering coefficient (Cp) and the characteristic path length (Lp). The measures were obtained during the different sleep stages and CAP conditions from the real EEG connectivity networks and randomized control (surrogate) networks (Cp-s and Lp-s). RESULTS: Cp and Cp/Cp-s increased significantly from wakefulness to sleep while Lp and Lp/Lp-s did not show changes. Cp/Cp-s was higher for A1 phases, compared to B phases of CAP. CONCLUSIONS: The network organization of the EEG slow-wave synchronization during sleep shows features characteristic of small-world networks (high Cp combined with low Lp); this type of organization is slightly but significantly more evident during the CAP A1 subtypes. SIGNIFICANCE: Our results show feasibility of using graph theoretical measures to characterize the complexity of brain networks during sleep and might indicate sleep, and the A1 phases of CAP in particular, as a period during which slow-wave synchronization shows optimal network organization for information processing.

Adult↗
PubMed1992

Reassessment of lead exposure in New Jersey using GIS technology.

In order to prevent children's exposure to lead, a variety of sources must be controlled. The New Jersey Department of Environmental Protection and Energy (NJDEPE) is using its Geographic Information System to identify areas within Newark, East Orange, and Irvington, New Jersey, where there may be greater environmental exposure to lead. Sensitive populations are identified through the U.S. Bureau of the Census information. Blood screening data provided by the New Jersey Department of Health (NJDOH) provide reported patterns of elevated blood lead in the study area. Comparisons of these spatial patterns will assist the NJDEPE in its soil sampling activities and lead exposure research, will provide information for public education, and will provide valuable information on sections of the study area where further screening and public education may be needed.

Air Pollutants↗
PubMed1993

The 3' regulatory region of the Abdominal-B gene: genetic analysis supports a model of reiterated and interchangeable regulatory elements.

The Abdominal-B (Abd-B) gene is one of three genes in the bithorax complex, a cluster of homeotic genes in Drosophila. During embryogenesis Abd-B is expressed in a complex pattern, producing four different transcript classes, each of which exhibits a unique spatial pattern of expression. Proper regulation of the class A transcripts is required for appropriate development of the fifth through eighth abdominal segments and is mediated, in part, by a 60-kb regulatory region located 3' of the gene. We have isolated a new mutation, designated Abd-BCorset, which is caused by a deletion that leaves 15 kb of the 3' regulatory sequences immediately adjacent to the gene, but removes 45 kb of the more distant 3' regulatory elements. This mutation produces an unexpected homeotic segmental transformation of the fourth through seventh abdominal segments, and has been analyzed by genetic and molecular techniques. In situ hybridization to Abd-BCorset embryos shows a uniform and moderate level of the Abd-B class A transcript in the posterior abdomen, rather than the normal graded pattern of expression. Our analysis of the Abd-BCorset mutation has prompted a model of the 3' regulatory region of Abd-B based on reiterated cell type-specific elements controlled by adjacent position-sensitive activating elements. The gradient of Abd-B expression normally observed in the posterior abdomen appears to be achieved by varying the number of reiterated elements that are active in each segment.

Animals↗
PubMed2006

Recent relative sea-level trends: an attempt to quantify the forcing factors.

Local sea-level is affected by a number of forcing factors, which all contribute to the trends observed by tide gauges. Here we use the fingerprints of main factors contributing to secular sea-level trends to construct an initial empirical model that explains best the trends in sea-level as recorded by the large number of coastal tide gauges over the last 50 years. The forcing factors considered include steric changes derived from observations, post-glacial rebound as predicted by geophysical models and mass changes in the Greenland and Antarctic ice sheets as predicted by the static sea-level equation. The approximation of the observed spatial pattern of sea-level trends through a model based on the spatial fingerprints of the main forcing factors fully utilizes the information contents of the available observations and models and allows the interpolation of the sea-level trends between the tide gauges. As a result, we obtain the global picture of sea-level trends due to the forcing factors accounted for in the analysis. Moreover, we derive constraints on the mass changes of the large ice sheets. The empirical models explain about 15% of the variance of the sea-level trends. Nevertheless, the models are correlated with the observations on the level of 0.38+/-0.07, indicating that most of the unexplained variance is due to contributions with small spatial scales. Averaged over the last five decades, the results indicate that the Antarctic and Greenland ice sheets have been melting with an equivalent contribution to global sea-level rise of 0.39+/-0.11 and 0.10+/-0.05 mm yr(-1), respectively. The steric signal derived from observations is clearly identified in the sea-level trends and is found to be at a minimum of 0.2 mm yr(-1), with the most likely value being close to 0.35 mm yr(-1). The global tide gauge network, which covers only a small fraction of the ocean surface, appears to sense an average sea-level rise larger than the global average. Extrapolating the regression models to the global ocean and taking into account the uncertainties in the extrapolation results in a most likely global average of the order of 1.05+/-0.75 mm yr(-1).

Climate↗
PubMed2003

Defect-suppressed atomic crystals in an optical lattice.

We present a coherent filtering scheme which dramatically reduces the site occupation number defects for atoms in an optical lattice by transferring a chosen number of atoms to a different internal state via adiabatic passage. With the addition of superlattices it is possible to engineer states with a specific number of atoms per site (atomic crystals), which are required for quantum computation and the realization of models from condensed matter physics, including doping and spatial patterns. The same techniques can be used to measure two-body spatial correlation functions.

Journal Article↗
PubMed2001

Similarity indices for spatial ecological data.

We present a method for assessing similarity between species maps of presence and absence or abundance that emphasizes global features while ignoring minor local dissimilarities. The method arranges sites into small groups, or cliques, and allows controlled changes to be made within cliques to reduce the influence of local discrepancies. Resulting measures of similarity are visually more satisfactory than traditional indices. We show that the similarity indices are useful for model selection by comparing observed spatial patterns with those predicted by different fitted models. Examples are provided for spatial distributions of oribatid mites (Acari, Oribatei), woodlarks (Lullula arborea), and red deer (Cervus elaphus).

Algorithms↗
PubMed2006

Comparative phylogeography of unglaciated eastern North America.

Regional phylogeographical studies involving co-distributed animal and plant species have been conducted for several areas, most notably for Europe and the Pacific Northwest of North America. Until recently, phylogeographical studies in unglaciated eastern North America have been largely limited to animals. As more studies emerge for diverse lineages (including plants), it seems timely to assess the phylogeography across this region: (i) comparing and contrasting the patterns seen in plants and animals; (ii) assessing the extent of pseudocongruence; and (iii) discussing the potential applications of regional phylogeography to issues in ecology, such as response to climatic change. Unglaciated eastern North America is a large, geologically and topographically complex area with the species examined having diverse distributions. Nonetheless, some recurrent patterns emerge: (i) maritime - Atlantic vs. Gulf Coast; (ii) Apalachicola River discontinuity; (iii) Tombigbee River discontinuity; (iv) the Appalachian Mountain discontinuity; (v) the Mississippi River discontinuity; and (vi) the Apalachicola River and Mississippi River discontinuities. Although initially documented in animals, most of these patterns are also apparent in plants, providing support for phylogeographical generalizations. These patterns may generally be attributable to isolation and differentiation during Pleistocene glaciation, but in some cases may be older (Pliocene). Molecular studies sometimes agree with longstanding hypotheses of glacial refugia, but also suggest additional possible refugia, such as the southern Appalachian Mountains and areas close to the Laurentide Ice Sheet. Many species exhibit distinct patterns that reflect the unique, rather than the shared, aspects of species' phylogeographical histories. Furthermore, similar modern phylogeographical patterns can result from different underlying causal factors operating at different times (i.e. pseudocongruence). One underemphasized component of pseudocongruence may result from the efforts of researchers to categorize patterns visually - similar patterns may, in fact, not fully coincide, and inferring agreement may obscure the actual patterns and lead to erroneous conclusions. Our modelling analyses indicate no clear spatial patterning and support the hypothesis that phylogeographical structure in diverse temperate taxa is complex and was not shaped by just a few barriers.

Animals↗
PubMed2004

Stratified growth in Pseudomonas aeruginosa biofilms.

In this study, stratified patterns of protein synthesis and growth were demonstrated in Pseudomonas aeruginosa biofilms. Spatial patterns of protein synthetic activity inside biofilms were characterized by the use of two green fluorescent protein (GFP) reporter gene constructs. One construct carried an isopropyl-beta-d-thiogalactopyranoside (IPTG)-inducible gfpmut2 gene encoding a stable GFP. The second construct carried a GFP derivative, gfp-AGA, encoding an unstable GFP under the control of the growth-rate-dependent rrnBp(1) promoter. Both GFP reporters indicated that active protein synthesis was restricted to a narrow band in the part of the biofilm adjacent to the source of oxygen. The zone of active GFP expression was approximately 60 microm wide in colony biofilms and 30 microm wide in flow cell biofilms. The region of the biofilm in which cells were capable of elongation was mapped by treating colony biofilms with carbenicillin, which blocks cell division, and then measuring individual cell lengths by transmission electron microscopy. Cell elongation was localized at the air interface of the biofilm. The heterogeneous anabolic patterns measured inside these biofilms were likely a result of oxygen limitation in the biofilm. Oxygen microelectrode measurements showed that oxygen only penetrated approximately 50 microm into the biofilm. P. aeruginosa was incapable of anaerobic growth in the medium used for this investigation. These results show that while mature P. aeruginosa biofilms contain active, growing cells, they can also harbor large numbers of cells that are inactive and not growing.

Anaerobiosis↗
PubMed1994

The effect of spatial orientation on the perception of moving tactile stimuli.

Previous studies have shown that the perception of spatial patterns, such as letters, presented to the hand is affected by the spatial orientation of the hand. The present study investigated how the perception of direction of motion across the fingerpads changes with the position of the hand in space. The moving stimuli were generated on two displays. In one condition, the displays were placed horizontally in front of the subject, with the subject's thumb (target site) and index finger (nontarget site) placed flat on the displays. In a second condition, the displays were vertically oriented and gripped between the thumb and index finger. Using a selective-attention paradigm in which subjects are instructed to respond only to the direction of motion at the target site, performance was still affected by the direction of motion at the nontarget site. Changing the orientation of the displays changed the effectiveness of the nontarget in interfering with the identification of the target movement. Nontarget stimuli that produced no interference in the horizontal orientation did so in the vertical, and vice versa. It appears that subjects are not using the local direction of movement across the fingerpads to judge the relative direction of movement at the two sites; rather, they are using the external direction of movement.

Attention↗
PubMed2003

[Application of geostatistical analysis in study of macrophytes community's pattern].

In this paper, the Log-log semivariogram and theoretical models of Geostatistics and fractal theory were applied to study the mosaic spatial pattern of macrophytes community and its different characters on different scales in littoral zone of the Baoan Lake, Hubei Province. The macrophytes in the littoral zone with a square area of 25,600 m2, which was divided in to 1,024 grids, were investigated, and the macrophytes species in every grid were recorded. If the species was discovered in the grid, the variable of the grid had a value of 1, otherwise, it was 0. The community had a value of the total species discovered in the grid. By the method, the sampling results of Vallisneria spiralis, Ceratophyllum oryzetorum, Myriophyllum spicatum and the community were made into four worksheets. With help of the software GS+ for Windows to treat these worksheets, we got their log-log semivariogram, isotropic model, anisotropic model, isotropic fractal dimension and anisotropic fractal dimension. According to the results of isotropic models, the exponential models of Vallisneria spiralis and Myriophyllum spicatum indicated their contagious distribution with a high proportion of spatial structure, which indicated that their distribution changed lesser at microscale. In their range of 48.6 m and 34.2 m respectively, they had a spatial autocorrelation. Isotropic models of Ceratophyllum oryzetorum and the community were linear, and their proportions of spatial structure were low, indicating their great change at microscale and their moderate contagious distribution. The isotropic fractal dimension and anisotropic fractal dimension results indicated the dominant pattern of Vallisneria spiralis in the direction of NE-SW, the dominant patterns of Myriophyllum spicatum and Ceratophyllum oryzetorum in the direction of N-S, and the community's dominant pattern in the direction of NW-SE. Compared with other analysis tools, the method had advantages in deciding whether the community components had a spatial autocorrelation and in quantitatively classifying the aggregation density. It provides us a new way to quantitatively describe the pattern of the macrophytes community.

Fresh Water↗
PubMed2004

Color shifts from S-cone patterned backgrounds: contrast sensitivity and spatial frequency selectivity.

Patterned backgrounds that selectively stimulate the S-cones cause conspicuous color shifts. These shifts are accounted for by an S-cone antagonistic (+S/-S) center-surround receptive field [Monnier, P., & Shevell, S. K. (2004). Chromatic induction from S-cone patterns. Vision Research, 44, 849-856]. The present study tested two additional implications of the S-cone receptive field for color shifts: (1) proportionality of the shifts with respect to S-cone contrast within the inducing pattern and (2) bandpass selectivity of the shifts with respect to the spatial frequency of the inducing pattern. Measurements showed that the magnitude of the color shift was linear with S-cone contrast and that the largest color shift was observed with inducing patterns at an intermediate spatial frequency. These results further support an S-cone spatially antagonistic receptive field as the neural substrate mediating the large color shifts from S-cone patterns.

Color Perception↗
PubMed1998

Spontaneous pinwheel annihilation during visual development.

Neurons in the visual cortex respond preferentially to edge-like stimuli of a particular orientation. It is a long-standing hypothesis that orientation selectivity arises during development through the activity-dependent refinement of cortical circuitry. Unambiguous evidence for such a process has, however, remained elusive. Here we argue that, if orientation preferences arise through activity-dependent refinement of initially unselective patterns of synaptic connections, this process should leave distinct signatures in the emerging spatial pattern of preferred orientations. Preferred orientations typically change smoothly and progressively across the cortex. This smooth progression is disrupted at the centres of so-called pinwheels, where neurons exhibiting the whole range of orientation preferences are located in close vicinity. Assuming that orientation selectivity develops through a set of rules that we do not specify, we demonstrate mathematically that the spatial density of pinwheels is rigidly constrained by basic symmetry principles. In particular, the spatial density of pinwheels, which emerge when orientation selectivity is first established, is larger than a model-independent minimal value. As a consequence, lower densities, if observed in adult animals, are predicted to develop through the motion and annihilation of pinwheel pairs.

Models, Biological↗
PubMed1990

Temporal order and tactile patterns.

Temporal order judgments (TOJs) were obtained for tactile stimuli presented to subjects' fingerpads. In one set of measurements, pairs of spatial patterns were presented successively to a single fingerpad (same-site condition), to two fingers on the same hand (ipsilateral condition), or to two fingers on opposite hands (bilateral condition). The subjects were instructed to report which one of the two patterns was presented first. TOJs were more accurate in the same-site condition than in either the ipsilateral or the bilateral conditions. In the ipsilateral and bilateral conditions, performance improved when judging which one of two locations received a stimulus first, although performance levels were still lower than in the same-site condition. Increasing the size of the pattern set from which the two patterns to be judged were drawn had only a slight effect on same-site performance and no effect on ipsilateral/bilateral performance; however, changing the nature of the patterns had a considerable effect on same-site performance and a smaller effect on ipsilateral/bilateral performance. Introducing an intensity imbalance between members of the pair of stimuli also had a large effect on same-site TOJs: a less intense stimulus tended to be judged as being presented first. In the bilateral condition, however, there was a small effect in the reverse direction: more intense stimuli tended to be judged as being presented first. The intensity imbalance had no effect in the ipsilateral condition. The results suggest that different mechanisms are responsible for TOJs for patterns presented to the same-site and to separate sites and, furthermore, that separate sites may constitute separate channels for spatial information.

Adult↗
PubMed1998

Optical recording system based on a fiber optic image conduit: assessment of microscopic activation patterns in cardiac tissue.

Optical recording of transmembrane voltage changes with the use of potentiometric dyes has opened the possibility of determining spatial patterns of electrical activity in excitable tissues. To follow such activation patterns on the cellular/subcellular level in heart cell cultures, a recording system was developed that features both high spatial resolution (4-200 microm) and high temporal resolution (uncertainty in the determination of delays between fast rising signals of +/-1 micros). Central to the system is a fiber optic image conduit consisting of 379 individual optical fibers. At one end the fibers are fused to form an input window that matches the size of the field of view of the microscope. At the other end, the fibers are loose, permitting a selectable subset to be connected to 80 discrete photodetectors. This design allows the sensitive area of the imager to be adapted to regions of interest in a given preparation, thus making optimal use of the limited number of detectors. Furthermore, by using a second fiber optic imager, individual photodetectors can be assigned to different optical ports, thus providing the means for fast and simultaneous dual-emission wavelength measurements. This feature permitted the elimination of motion artifacts arising from the myocytes without the use of contraction-suppressing drugs.

Action Potentials↗
PubMed1987

Cranial variation in European populations: a spatial autocorrelation study at three time periods.

This study reports on spatial variation of 10 cranial variables in European populations at 3 time periods. Means for these variables, based on 137, 108, and 183 samples from the Early Medieval, Late Medieval, and Recent periods, were subjected to one-dimensional and directional spatial autocorrelation analyses. Significant spatial structure was found for most variables. It becomes more pronounced as time progresses. The spatial patterns are not strongly clinal. Correlograms based on distances computed from all variables are monotonic only to 900, 1,650, and 1,350 km for the three periods. Regional patterns are seen for most variables and become more structured and significant with time. There is little similarity among the correlograms of the variables at any one period and virtually none among periods. Inferences about spatial structure of these populations, based on spatial autocorrelation analysis, suggest a pattern dominated by migration, followed by expansion and admixture rather than selection or chance fluctuations. The patterns of morphometric change seem to reflect the patterns of linguistic change in these areas.

Cephalometry↗
PubMed2005

Pigment cell distributions in different tissues of the zebrafish, with special reference to the striped pigment pattern.

The orderly pigment pattern of zebrafish (Danio rerio) is a good model system for studying how spatial patterns form in animals. Recent molecular genetic studies have shown that interactions between the pigment cells play major roles in pattern formation. In the present study, we performed comparative transmission electron microscopy of pigment cells, in order to clarify the structural interactions of pigment cells in tissues with and without a striped pattern. In patterned tissues, pigment cells were distributed as a one-cell-thick sheet. The layer order of the sheets is always kept strictly. In tissues without a striped pattern, the layer order was often disturbed or the cells were distributed in a scattered, double-sheeted, or an accumulated pile. Our observations suggest that the underlying mechanism that controls the vertical order of the pigment cells is related to that controlling the stripe pattern.

Animals↗
PubMed1990

Psychophysical measures from electrical stimulation of the human cochlear nucleus.

Auditory performance on basic psychophysical tasks was measured in ten deaf patients with electrodes positioned near their cochlear nucleus. The device is called the auditory brainstem implant (ABI). Electrodes were placed during surgery to remove an acoustic neuroma, which results in the removal of the VIII nerve and, thus deafness. In patients who received auditory sensation from electrical stimulation we measured auditory performance on standard psychophysical tasks: thresholds, loudness growth, intensity discrimination, temporal integration, temporal modulation detection, gap detection, and forward masking. Plots of threshold as a function of frequency or biphasic pulse duration were markedly different from those of patients with cochlear implants. The difference in threshold functions is probably partly due to the biophysical difference in the neural elements stimulated. Another possibility is that part of the difference is due to the highly abnormal spatial pattern of activation in the cochlear nucleus from electrical stimulation, which prevents normal spatial integration of activity. The usable range of electrical amplitudes above threshold is comparable with that of cochlear implants, typically 10-15 dB. Little temporal integration occurs over a range of stimulus durations from 2-1000 ms. When compared at equivalent loudness levels, gap detection thresholds are similar to, or a bit longer than, gap thresholds in normal-hearing listeners and cochlear implant patients. Forward masking recovery functions are similar to those of normal listeners and cochlear implant patients. Patients' ability to detect amplitude modulation as a function of modulation frequency is similar to that of cochlear implant patients and normal listeners. Thus, direct electrical stimulation of the brainstem produces temporal resolution that does not significantly differ from that of normal listeners when compared in equivalent amplitude units. This implies that the limiting factors for these tasks are more centrally located, and not directly related to threshold mechanisms. Thus, a properly designed speech processor could preserve the important temporal features of speech for these patients.

Adolescent↗