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At least 343 records · Page 19Linked to original sources
PubMed2004

Motion-based analysis of spatial patterns by the human visual system.

BACKGROUND: It is known that the visibility of patterns presented through stationary multiple slits is significantly improved by pattern movements. This study investigated whether this spatiotemporal pattern interpolation is supported by motion mechanisms, as opposed to the general belief that the human visual cortex initially analyses spatial patterns independent of their movements. RESULTS: Psychophysical experiments showed that multislit viewing could not be ascribed to such motion-irrelevant factors as retinal painting by tracking eye movements or an increase in the number of views by pattern movements. Pattern perception was more strongly impaired by the masking noise moving in the same direction than by the noise moving in the opposite direction, which indicates the direction selectivity of the pattern interpolation mechanism. A direction-selective impairment of pattern perception by motion adaptation also indicates the direction selectivity of the interpolation mechanism. Finally, the map of effective spatial frequencies, estimated by a reverse-correlation technique, indicates observers' perception of higher spatial frequencies, the recovery of which is theoretically impossible without the aid of motion information. CONCLUSIONS: These results provide clear evidence against the notion of separate analysis of pattern and motion. The visual system uses motion mechanisms to integrate spatial pattern information along the trajectory of pattern movement in order to obtain clear perception of moving patterns. The pattern integration mechanism is likely to be direction-selective filtering by V1 simple cells, but the integration of the local pattern information into a global figure should be guided by a higher-order motion mechanism such as MT pattern cells.

Adult↗
PubMed2004

[Spatial pattern analysis of forest landscape in low coteau of middle Qilian Mountains].

Based on the vegetation map and the relief map, using GIS and Fragstats, the spatial pattern of forest landscape of Xishui reserve in Qilian Mountains were analyzed. The results showed that the distribution of the vegetation was impacted mostly by altitude and aspect, grasslant was mostly distributed on the land of altitude 2,500-2,900 m and aspect of south and southwest, Picea crassifolia forest was always in the land of altitude 2,900-3,300 m and aspect of north, northeast, east and northwest, and shrubbery was in the land of altitude 3,300-3,700 m. The grassland had the biggest area and its connectivity and integrality were the best. The biggest MPFD of Picea crassifolia forest meant that its shape was the most complicated, its mean patch area was small, and the distance between the patches was short. So Picea crassifolia forest was easy to be impacted by some disturbance. The forest suitable land and Sabina przewalskii forest showed more outstretched characteristics than farmland and land with few trees. The mean nearest-neighbor distance of the poplar forest was the biggest in all the landscape elements, so the poplar forest's fragmentized degree was the highest in all the landscape elements.

Conservation of Natural Resources↗
PubMed1998

Factors influencing malaria endemicity in Yunnan Province, PR China (analysis of spatial pattern by GIS). Geographical Information System.

This study is an initial attempt to apply disease mapping through Geographical Information System (GIS) with multiple regression analysis to determine the nature and extent of factors influencing malaria transmission in Yunnan Province, PR China, particularly in border areas. Secondary county-based data covering the period 1990 to 1996 were collected and analyzed. The malaria situation in Yunnan Province as a whole is influenced mainly by the combined effects of the physical environment, the presence of efficient vector species, and mobile population along international borders with Myanmar, Lao PDR and Vietnam.

China↗
PubMed2005

Analysis of spatial correlation between 99mTc-Sestamibi uptake and radiographic breast density.

Breast scintigraphy is a technique by which the biological properties of breast lesions can be assessed using an injected radiopharmaceutical. It may be particularly useful for women with radiographically dense breasts, in whose mammograms, lesions are often obscured by breast tissue. We are evaluating a dual modality breast scanner developed at the University of Virginia for its ability to distinguish between benign and malignant lesions. The scanner obtains a digital mammogram and a gamma ray emission image in quick succession with the breast held under mild compression, resulting in a fused image in which structures in the digital mammogram can be directly correlated with those in the scintigram. Our experience has shown that radiopharmaceutical uptake by normal breast tissue can sometimes obscure uptake by small lesions. It would therefore be advantageous to correct for this background uptake if possible. One potential way of accomplishing this is to use the information from the digital mammogram to help predict the background radiopharmaceutical distribution. With this in mind, we retrospectively investigated the degree of spatial correlation between the distribution of background activity and the distribution of radiodense breast tissue in normal breasts. Using a histogram-based analysis, we have quantified the degree of correlation in 16 images obtained from a total of 8 patients. We also used the mammographic images to quantify the radiographic density of each breast. Our results suggest that spatial correlation between areas of high radiopharmaceutical uptake and parenchymal density exists in the most dense regions of the breast for either extremely dense or heterogeneously dense breasts. High correlation was also observed for some homogeneously fatty breasts. In the latter case however, variation in breast thickness appeared to be the cause of the increased correlation. Correlation properties are approximately equal in both right and left breasts for a particular patient, except in cases exhibiting focal radiotracer uptake in a lesion. Although our preliminary results suggest that correlation between radiopharmaceutical uptake and parenchymal density exists, the number of cases thus far is too small for definitive conclusions. In addition, the planar nature of the dual modality scans imposes an inherent limitation on our ability to take into account attenuation of the emitted gamma radiation, which thus constitutes an uncontrolled variable in the correlation analysis. In principle, this problem can be eliminated by 3-dimensional imaging.

Adipose Tissue↗
PubMed1998

Spatial chemical analysis of dental stain using wavelength dispersive spectrometry.

Six extracted human teeth with naturally-formed neglected stain were analyzed for chemical constituents using wavelength dispersive spectrometry (WDS), an electron microprobe technique. Spatial distribution, within a few microm resolution, of the compositional elements was obtained by line and map analyses, which provided relative concentrations of the elements in stain-enamel complex. Absolute concentrations at different locations across a specimen were obtained from quantitative analysis. Results showed that these neglected stains were highly calcified and contained a significant amount of organic matter (C, N, O, S), with traces of Fe and Cu. The tooth surface underneath the stain layer could be easily distinguished by the higher Ca and P content, as well as by finite amounts of C and S. Corresponding areas of high concentrations between S and Fe/Cu were observed, which suggested the complex of sulfur and metal ions as possible color-forming species. S was found to diffuse into surface enamel in the range of 10 microm.

Calcinosis↗
PubMedDate not supplied

[Analysis of spatial diffusion patterns for AIDS cases in some Brazilian States].

Despite new improvements in AIDS treatment, preventive measures are still essential to control the epidemic. Effective programs almost always depend on correct and efficient allocation of scarce health resources. Detailed information on the epidemic, such as where, when, and how the epidemic will spread are of great value. This study was conducted to obtain a better understanding of the dissemination of AIDS cases in four important Brazilian States. Spatial diffusion patterns were evaluated qualitatively by studying sequential maps and quantitatively by analyzing spatial correlograms. Ten years were analyzed, grouped in three periods (1987-1989, 1990-1992, and 1993-1996). The diffusion process was studied for both total AIDS cases and male and female cases. Diffusion of AIDS cases presented specific characteristics for each of the four States. Information derived from the study, especially the results of the correlogram analysis, improve our understanding of the epidemic's spatial diffusion in different parts of the country and can also be used to determine parameters for other AIDS epidemiological models.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Spatial pattern analysis of functional brain images using partial least squares.

This paper introduces a new tool for functional neuroimage analysis: partial least squares (PLS). It is unique as a multivariate method in its choice of emphasis for analysis, that being the covariance between brain images and exogenous blocks representing either the experiment design or some behavioral measure. What emerges are spatial patterns of brain activity that represent the optimal association between the images and either of the blocks. This process differs substantially from other multivariate methods in that rather than attempting to predict the individual values of the image pixels, PLS attempts to explain the relation between image pixels and task or behavior. Data from a face encoding and recognition PET rCBF study are used to illustrate two types of PLS analysis: an activation analysis of task with images and a brain-behavior analysis. The commonalities across the two analyses are suggestive of a general face memory network differentially engaged during encoding and recognition. PLS thus serves as an important extension by extracting new information from imaging data that is not accessible through other currently used univariate and multivariate image analysis tools.

Algorithms↗
PubMedDate not supplied

[The effect of the duration of mental work on problem solving in mental rotation].

Effect of sustained mental work on the first stage of mental rotation was studied by the method of intracortical interaction. It was revealed that during sustained mental work the zone of the high level of connections in the alpha-band was considerably reduced due to an increase of specificity, rationality of thinking. In the beta-band the zone of the high connection level moved from the central and parietal areas to the anterior regions because of a switch of intention of the mental work from the spatial analysis to the quick verbalization of the response. Tired subjects in search for a word for the response did not fulfil the spatial analysis of the pictures. Subjects with high working ability searched for the verbal response on the basis of mental operations with images, that turned to be optimal for the mental rotation task solving.

Adult↗
PubMed1995

A frequency domain analysis of spatial organization of epicardial maps.

Mapping of organized rhythms like sinus rhythm uses activation times from individual electrograms, and often assumes that the map for a single activation is similar to maps for subsequent activations. However, during fibrillation, activation times and electrograms are not easy to define, and maps change from activation to activation. Volume and complexity of data make analysis of more than a few seconds of fibrillation difficult. Magnitude Squared Coherence (MSC), a frequency domain measure of the phase consistency between two signals, can be used to help interpret longer data segments without defining activation times or electrograms. Sinus rhythm, flutter, and fibrillation in humans and swine were mapped with an array of unipolar electrodes (2.5 mm apart) at 240 sites on the atrial or ventricular epicardium. Four-second data segments were analyzed. One site near the center of the array was chosen ad hoc as a reference. MSC maps were made by measuring mean MSC from 0-50 Hz between every point in the array relative to the reference. Isocoherence contours were drawn. The effects of bias in the coherence estimate due to misalignment were investigated. Average MSC versus distance from the reference was measured for all rhythms. Results indicate that in a 4-s segment of fibrillation, there can exist some phase consistency between one site and the reference and little or none between a second site and the reference even when both sites are equidistant from the reference. In fibrillation, isocoherence contours are elongated and irregularly shaped, reflecting long-term, but nonuniform, spatial organization. That is, activation during fibrillation cannot be considered as random over a 4-s interval. Bias in the coherence estimate due to misalignment is significant for sinus rhythm and flutter, but can be corrected by manual realignment. Average MSC drops with distance for all rhythms, being most pronounced for fibrillation, MSC maps may provide insights into long-term spatial organization of rhythms that would otherwise be cumbersome and difficult to interpret with standard time domain analysis.

Animals↗
PubMed1993

Molecular analysis and spatial expression pattern of a low-temperature-specific barley gene, blt101.

A cDNA clone of the previously unreported low-temperature-induced gene blt101 was isolated after a differential screen of a cDNA library prepared from low-temperature (6 degrees C day/2 degrees C night) grown barley shoot meristems. Southern blot analysis of barley ditelosomic addition lines was used to assign this single-copy gene to the long arm of chromosome 4. Analysis of steady-state levels of blt101 mRNA showed the induction of this transcript in shoot meristems upon transfer of barley (cv. Igri) plants from control (20 degrees C/15 degrees C) to low (6 degrees C/2 degrees C) temperature treatment. Further, the high level of this transcript is maintained at low temperatures but is reduced on transfer from low to control temperatures. The gene is not induced by drought or by foliar application of ABA. Analysis of segregating doubled haploid lines shows that there is no specific association of this gene with either spring/winter growth habit or frost hardiness. Examination of the spatial expression pattern revealed ubiquitous expression of blt101 in low-temperature (6 degrees C/2 degrees C) grown barley shoot meristems, mature leaves and roots.

Abscisic Acid↗
PubMed1993

European isolation and confinement study. Ethological analysis of spatial behavior.

The purpose of this study was to evaluate through an ethological approach the behavioral consequences of confinement and isolation in the restricted space of a hyperbaric chamber at low pressure on six subjects for a period of 28 days. The quantitative analysis consisted in tracing the use of space, minute by minute (i.e., groupings of positions and displacement trajectories) and counting the motor activity (i.e., collateral acts) of the crew members while performing various tasks (meeting, preparing dinner, dinner, leisure time) within the main chamber as a function of the time spent in confinement (days 2, 9, 19, 28). The data reveal a change in the timing of collective tasks in the course of the experiment, a dispersal of the social group during the middle period, and a stability of the spatial behavior at the beginning and at the end of the isolation period. Other behavioral strategies observed are the necessity of body mobility in a reduced space, the decrease of an intimate space as defined by Hall, with the predominance of a social space first and a personal space later with increasing time of confinement. Consequently, the crew members appear to adapt by means of these behavioral strategies. In that way, the reduction in the number of collateral activities can be taken as an index of the adaptation of the subjects to these extreme conditions.

Group Processes↗
PubMed2004

Spatial pattern analysis of nitrergic neurons in the developing myenteric plexus of the human fetal intestine.

BACKGROUND: Enteric nervous system precursors derived from the neural crest migrate along defined pathways to colonize the bowel. The individual cells in different environments experience different growth, differentiation, and survival conditions. Hence, the spatial distribution of the neurons is determinant with regard to functional maturation. The question arises as to whether the distribution is random or nonrandom. METHODS: Nitrergic cells were visualized by means of nicotinamide adenine dinucleotide phosphate diaphorase histochemistry. Stained specimens were photographed, and the borders of the myenteric plexus and the nuclei of the nitrergic neurons were digitalized. Plexus Pattern Analysis software was used to count the nuclei of nitrergic neurons, calculate the proportions of the areas covered by the plexus and the gut wall, and perform randomization analyses. RESULTS: The distribution pattern of the nitrergic neurons changed markedly between weeks 14 and 22 of gestation. The nitrergic neurons were randomly distributed at week 14 but were aggregated in the plexus and within the individual ganglia at week 19. The dynamics of these changes exhibited regional differences. CONCLUSIONS: The results suggest that, in addition to the gut wall and the plexus, other intraganglionic constituents may contribute to the aggregation of nitrergic cells and such examinations should be extended to other cell types in the future.

Female↗
PubMed2004

Intra-household clustering of hepatitis C virus infection in Karachi, Pakistan.

Transmission rates of hepatitis C virus (HCV) infection through non-sexual household contacts have been considered to be very low. This study evaluated intra-household clustering of cases of HCV infection in a low socio-economic community in Karachi, Pakistan. Serum samples from 341 household contacts of 86 thalassaemic HCV-seropositive children were evaluated for antibodies to HCV using an ELISA. Spatial analysis of data was carried out to test for intra-household clustering. Seventy of 341 (20.5%) household contacts were HCV-seropositive. Of the households studied, 44.2% (38/86) had one or more contacts who tested HCV-seropositive. Ecological analysis of variables at household level showed that in households where HCV-seropositive index thalassaemic children were male HCV tended to be transmitted to one or more familial contacts. Spatial analysis with an asymptotic score test of the null hypothesis of no extra within-family infectivity revealed that there was a significant tendency of HCV infection to cluster within a household (score statistic = 19.44, P=0.032). The results showed that non-sexual household exposure may play a role in efficient HCV spread to household contacts of HCV-infected persons and needs further evaluation.

Adolescent↗
PubMed2004

[Spatial-statistical analysis of infectious disease notification data in lower saxony].

BACKGROUND: In Lower Saxony the analysis of notification data according to the infection protection law is based on two pillars: one pillar is the weekly analysis to identify clusters and locally non-detectable outbreaks by an early warning system. The second pillar is an annual reporting system for obtaining an overall picture and for identifying long-term trends. In both fields methods of spatial statistics are applied. METHODS: For the 16 most frequent notifiable diseases, the notification data of the districts of Lower Saxony are analysed and presented on the Internet. The presentation starts with an overview page, on which differences between observed and expected case counts for these diseases are presented tabulated and graphically. On a separate page for each disease the temporal and spatial distribution is shown by means of the following graphs: Time series presentation (weekly case counts and moving averages), chloropleth map of regional incidence rates and dot map of regional case counts. For identification of outbreaks, Kulldorff's "scan statistic" is used to search the data for clusters and to assess the significance of these clusters. The methods are executed mainly automatically using predominantly public domain software. RESULTS AND DISCUSSION: The approach attempts to meet the surveillance principle of providing the participants with immediate feedback. The scan statistics is a universal objective instrument for detecting and assessing spatial clusters. A special advantage is the identification of clusters which include several districts. The properties of the identified clusters (spatial extension, number of cases) offer some insight into the characteristic epidemiology of the diseases.

Cluster Analysis↗
PubMed1996

Differential visuospatial dysfunction following striatal, frontal white matter, or posterior thalamic infarction.

The present study investigated visuospatial functioning in 35 right-hand dominant patients with striatal, frontal white matter, or posterior thalamic infarction, in the right cerebral hemisphere. On tasks of visual detection and discrimination, the groups performed within normal limits and comparable to one another. On tasks of visual synthesis and spatial analysis, each group was significantly impaired, with greatest impairment following infarction of deep grey structures. Correlational analyses indicated that in the striatal and frontal white matter groups, visual synthesis and spatial analysis task performance were strongly correlated with performance on neuropsychological tests of executive control. This relationship was not observed in the posterior thalamic group. The results support the hypothesis of differential patterns of visuospatial performance depending on the anatomical locus of subcortical lesions. The findings are explained in terms of differing subcortical circuitry and suggest that multiple substrates mediate the sequelae of subcortical lesions.

Aged↗
PubMed1991

Second-order analysis of spatial clustering for inhomogeneous populations.

Motivated by recent interest in the possible spatial clustering of rare diseases, the paper develops an approach to the assessment of spatial clustering based on the second-moment properties of a labelled point process. The concept of no spatial clustering is identified with the hypothesis that in a realisation of a stationary spatial point process consisting of events of two qualitatively different types, the type 1 events are a random sample from the superposition of type 1 and type 2 events. A diagnostic plot for estimating the nature and physical scale of clustering effects is proposed. The availability of Monte Carlo tests of significance is noted. An application to published data on the spatial distribution of childhood leukaemia and lymphoma in North Humberside is described.

Biometry↗