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PubMed2002

The perception of breast cancer: what differentiates missed from reported cancers in mammography?

RATIONALE AND OBJECTIVES: Mammographers map endogenous and exogenous factors into decisions whether to report the presence of a malignant finding in a mammogram case. Thus, to understand how image-based elements are translated into observer-based decisions, the authors used spatial frequency analysis to model the areas on mammograms that attracted visual attention, in addition to the areas localized as abnormal. MATERIALS AND METHODS: Four mammographers read 40 two-view mammogram cases, of which 30 contained at least one malignant lesion visible on one or two views. Their eye positions were recorded during visual search. Once the mammographer felt confident enough to provide an initial impression of the case ("normal" or "abnormal"), the eye position monitoring was turned off and the mammographer indicated, with a mouse-controlled cursor, the location and nature of any malignant findings. Regions that elicited an overt or a covert response by the mammographers were extracted for processing by means of wavelet packets and artificial neural networks. RESULTS: Different decision outcomes yielded different energy representations, in the spatial frequency domain. These energy representations were used by an artificial neural network to predict decision outcome in areas of interest, derived from eye position analysis, on mammograms from new cases. Individual trends were observed for each mammographer. CONCLUSION: Spatial frequency representation of regions that attracted a given mammographer's visual attention may be useful for characterizing how that mammographer will respond to the visually selected areas.

Analysis of Variance↗

PubMed1989

Quantifying capillary distribution in four dimensions.

Analysis of spatial distribution using numerical (O-D) distribution is limited to global estimates, while linear (1-D) separation of capillaries may be used to describe unrealistic spatial patterns. Intramuscular diffusion is best viewed as an integration of all distances between surrounding capillaries, or area (2-D) of influence for individual vessels. True planar analysis also accommodates other forms of heterogeneity, and may be extrapolated to give the volume (3-D) of tissue supplied by capillaries. Temporal (4-D) heterogeneity in functional spacing may then be quantified.

Animals↗

PubMed1996

Modeling regional myocardial flows from residue functions of an intravascular indicator.

The purpose of the present study was to determine the accuracy and the sources of error in estimating regional myocardial blood flow and vascular volume from experimental residue functions obtained by external imaging of an intravascular indicator. For the analysis, a spatially distributed mathematical model was used that describes transport through a multiple-pathway vascular system. Reliability of the parameter estimates was tested by using sensitivity function analysis and by analyzing "pseudodata": realistic model solutions to which random noise was added. Increased uncertainty in the estimates of flow in the pseudodata was observed when flow was near maximal physiological values, when dispersion of the vascular input was more than twice the dispersion of the microvascular system for an impulse input, and when the sampling frequency was < 2 samples/s. Estimates of regional blood volume were more reliable than estimates of flow. Failure to account for normal flow heterogeneity caused systematic underestimates of flow. To illustrate the method used for estimating regional flow, magnetic resonance imaging was used to obtain myocardial residue functions after left atrial injections of polylysine-Gd-diethylenetriaminepentaacetic acid, an intravascular contrast agent, in anesthetized chronically instrumental dogs. To test the increase in dispersion of the vascular input after central venous injections, magnetic resonance imaging data obtained in human subjects were compared with left ventricular blood pool curves obtained in dogs. It is concluded that if coronary flow is in the normal range, when the vascular input is a short bolus, and the heart is imaged at least once per cardiac cycle, then regional myocardial blood flow and vascular volume may be reliably estimated by analyzing residue functions of an intravascular indicator, providing a noninvasive approach with potential clinical application.

Animals↗

PubMed2005

Object versus spatial visual mental imagery in patients with schizophrenia.

OBJECTIVE: Recent research has revealed a larger impairment of object perceptual discrimination than of spatial perceptual discrimination in patients with schizophrenia. It has been suggested that mental imagery may share processing systems with perception. We investigated whether patients with schizophrenia would show greater impairment regarding object imagery than spatial imagery. METHODS: Forty-four patients with schizophrenia and 20 healthy control subjects were tested on a task of object visual mental imagery and on a task of spatial visual mental imagery. Both tasks included a condition in which no imagery was needed for adequate performance, but which was in other respects identical to the imagery condition. This allowed us to adjust for nonspecific differences in individual performance. RESULTS: The results revealed a significant difference between patients and controls on the object imagery task (F(1,63) = 11.8, p = 0.001) but not on the spatial imagery task (F(1,63) = 0.14, p = 0.71). To test for a differential effect, we conducted a 2 (patients v. controls) small ha, Cyrillic 2 (object task v. spatial task) analysis of variance. The interaction term was statistically significant (F(1,62) = 5.2, p = 0.026). CONCLUSIONS: Our findings suggest a differential dysfunction of systems mediating object and spatial visual mental imagery in schizophrenia.

Adult↗

PubMedDate not supplied

[Situational conditioned reflexes in intact and callosotomized dogs when the location of conditioned and unconditioned stimuli is changed].

Positive and inhibitory conditioned reflexes were elaborated to signals, presented at the same display. Discrimination between spatially joined signals turned out to be a difficult task for intact and, in particular, for callosectomized dogs, who showed disturbances of the higher nervous activity. The analysis of spatially joined signals is possible for animals, previously trained in experiments with spatial separation of signals. With changed position of conditioned and unconditioned stimuli the callosectomized animals develop an inertness of nervous processes, manifested in a prolonged afteraction of the previously formed activity in an increased number of inadequate reactions, and impairment of differentiations.

Animals↗

PubMed1996

Effect of window size on detection acuity and resolution acuity for sinusoidal gratings in central and peripheral vision.

Detection and resolution of square patches of sinusoidal gratings were measured in central and peripheral vision (30 degrees horizontal temporal visual field) for high-contrast gratings as a function of the number of cycles in the stimulus. We determined performance in a forced-choice paradigm for a fixed number of stimulus cycles by arranging for stimulus diameter to vary inversely with spatial frequency. For both psychophysical tasks and for both target locations, the psychometric function relating performance to log spatial frequency shifted to higher frequencies without changing slope significantly as the number of cycles in the stimulus was increased. Thus the entire effect could be captured by an analysis of spatial acuity, which increased with increasing number of grating cycles over the range 0.5-6 cycles but remained constant over the range 6-14 cycles. In the central field, resolution acuity and detection acuity were equal regardless of the number of cycles in the stimulus. In the peripheral field, detection acuity exceeded resolution acuity and perceptual aliasing occurred for stimuli in the range 1-14 cycles. From this result we conclude that resolution acuity is sampling limited in the periphery, provided that the stimulus contains at least one full cycle of the grating. Essential features of the results could be accounted for by Fourier analysis of the stimulus.

Fovea Centralis↗

PubMed2005

[Spatial distribution pattern and fractal analysis of Larix chinensis populations in Qinling Mountain].

In this paper, the fractal characters of Larix chinensis populations in Qinling Mountain were studied by contiguous grid quadrate sampling method and by boxing-counting dimension and information dimension. The results showed that the high boxing-counting dimension (1.8087) and information dimension (1.7931) reflected a higher spatial occupational degree of L. chinensis populations. Judged by the dispersal index and Morisita's pattern index, L. chinensis populations clumped at three different age stages (0-25, 25-50 and over 50 years). From Greig-Smiths' mean variance analysis, the figure of pattern scale showed that L. chinensis populations clumped in 128 m2 and 512 m2, and the different age groups clumped in different scales. The pattern intensities decreased with increasing age, and tended to reduce with increasing area when detected by Kershaw's PI index. The spatial pattern characters of L. chinensis populations may be their responses to environmental factors.

China↗

PubMed1990

Nerve growth factor levels and choline acetyltransferase activity in the brain of aged rats with spatial memory impairments.

Nerve growth factor (NGF) and choline acetyltransferase (ChAT) activity levels were measured in 7 different brain regions in young (3-month-old) and aged (2-years-old) female Sprague-Dawley rats. Prior to analysis the spatial learning ability of the aged rats was assessed in the Morris' water maze test. In the aged rats a significant, 15-30%, increase in NGF levels was observed in 4 regions (septum, cortex, olfactory bulb and cerebellum), whereas the levels in hippocampus, striatum and the brainstem were similar to those of the young rats. The NGF changes did not correlate with the behavioral performance within the aged group. Minor 15-30%, changes in ChAT activity were observed in striatum, brainstem and cerebellum, but these changes did not correlate with the changes in NGF levels in any region. The results indicate that brain NGF levels are maintained at normal or supranormal levels in rats with severe learning and memory impairments. The results, therefore, do not support the view that the marked atrophy and cell loss in the forebrain cholinergic system that is known to occur in the behaviorally impaired aged rats is caused by a reduced availability of NGF in the cholinergic target areas. The results also indicate that the slightly increased levels of NGF are not sufficient to prevent the age-dependent atrophy of cholinergic neurons, although they might be important for the stimulation of compensatory functional changes in a situation where the system is undergoing progressive degeneration.

Aging↗

PubMed2006

Vector-based spatial-temporal minimum L1-norm solution for MEG.

Minimum L1-norm solutions have been used by many investigators to analyze MEG responses because they provide high spatial resolution images. However, conventional minimum L1-norm approaches suffer from instability in spatial construction, and poor smoothness of the reconstructed source time-courses. Activity commonly "jumps" from one grid point to (usually) the neighboring grid points. Equivalently, the time-course of one specific grid point can show substantial "spiky-looking" discontinuity. In the present study, we present a new vector-based spatial-temporal analysis using a L1-minimum-norm (VESTAL). This approach is based on a principle of MEG physics: the magnetic waveforms in sensor-space are linear functions of the source time-courses in the imaging-space. Our computer simulations showed that VESTAL provides good reconstruction of the source amplitude and orientation, with high stability and resolution in both the spatial and temporal domains. "Spiky-looking" discontinuity was not observed in the source time-courses. Importantly, the simulations also showed that VESTAL can resolve sources that are 100% correlated. We then examined the performance of VESTAL in the analysis of human median-nerve MEG responses. The results demonstrated that this method easily distinguishes sources very spatially close to each other, including individual primary somatosensory areas (BA 1, 2, 3b), primary motor area (BA 4), and other regions in the somatosensory system (e.g., BA 5, 7, SII, SMA, and temporal-parietal junction) with high temporal stability and resolution. VESTAL's potential for obtaining information on source extent was also examined.

Adult↗

PubMed1997

The effect of nonspatial water maze pretraining in rats subjected to serotonin depletion and muscarinic receptor antagonism: a detailed behavioural assessment of spatial performance.

A detailed behavioural analysis of water maze spatial performance in the rat was utilized to determine the effect of single and combined administration of p-chlorophenylalanine (PCPA; 1000 mg/kg, i.p.), an inhibitor of serotonin biosynthesis, and scopolamine hydrobromide (SCO; 1.0 mg/kg, i.p.), a muscarinic receptor antagonist. In some groups a water maze pretraining regimen known as non-spatial pretraining (NSP) was used to familiarize the animals with the general requirements of the task before spatial training was begun. The results showed that: (a) depletion of serotonin with PCPA had no effect on water maze performance and produced no sensorimotor disturbances; (b) antagonism of muscarinic receptors produced impairments in spatial and sensorimotor function in naive rats but neither effect was observed in rats first given NSP; (c) combined disruption of muscarinic and serotonergic function produced a severe deficit in spatial performance that was only partially alleviated by NSP; and (d) there was an association between poor maze acquisition scores and a high incidence of sensorimotor dysfunction. In addition to the water maze task the rats were also assessed for motoric performance on a beam walking test. The role of cholinergic and serotonergic systems in learning and memory is discussed.

Animals↗

PubMed2003

Characterization of PTM5 in aspen trees: a MADS-box gene expressed during woody vascular development.

The vascular component of trees possesses some of the most specialized processes active in the formation of roots, stems, and branches, and its wood component continues to be of primary importance to our daily lives. The molecular mechanisms of wood development, however, remain poorly understood with few well-characterized regulatory genes. We have identified a vascular tissue-specific MADS-box gene, Populus tremuloides MADS-box 5 (PTM5) that is expressed in differentiating primary and secondary xylem and phloem. Phylogenetic analysis has shown that PTM5 is a member of the SOC1/TM3 class of MADS-box genes. Temporal expression analysis of PTM5 in staged vascular cambium and other tissues indicated that PTM5 expression is seasonal and is limited to spring wood formation and rapidly expanding floral catkins. Spatial expression analysis using in situ hybridization revealed that PTM5 expression is localized within a few layers of differentiating vascular cambium and xylem tissues as well as the vascular bundles of expanding catkins. Since many MADS-box genes are known to act as transcription factors, these results suggest that the coordinated expression of PTM5 with other vascular developmental genes may be a hallmark of the complex events that lead to the formation of the woody plant body.

Amino Acid Sequence↗

PubMed2001

Genetic differentiation in South Amerindians is related to environmental and cultural diversity: evidence from the Y chromosome.

The geographic structure of Y-chromosome variability has been analyzed in native populations of South America, through use of the high-frequency Native American haplogroup defined by the DYS199-T allele and six Y-chromosome-linked microsatellites (DYS19, DYS389A, DYS389B, DYS390, DYS391, and DYS393), analyzed in 236 individuals. The following pattern of within- and among-population variability emerges from the analysis of microsatellite data: (1) the Andean populations exhibit significantly higher levels of within-population variability than do the eastern populations of South America; (2) the spatial-autocorrelation analysis suggests a significant geographic structure of Y-chromosome genetic variability in South America, although a typical evolutionary pattern could not be categorically identified; and (3) genetic-distance analyses and the analysis of molecular variance suggest greater homogeneity between Andean populations than between non-Andean ones. On the basis of these results, we propose a model for the evolution of the male lineages of South Amerindians that involves differential patterns of genetic drift and gene flow. In the western part of the continent, which is associated with the Andean area, populations have relatively large effective sizes and gene-flow levels among them, which has created a trend toward homogenization of the gene pool. On the other hand, eastern populations-settled in the Amazonian region, the central Brazilian plateau, and the Chaco region-have exhibited higher rates of genetic drift and lower levels of gene flow, with a resulting trend toward genetic differentiation. This model is consistent with the linguistic and cultural diversity of South Amerindians, the environmental heterogeneity of the continent, and the available paleoecological data.

Cultural Diversity↗

PubMed2000

C-terminal domains of Escherichia coli topoisomerase I belong to the zinc-ribbon superfamily.

Detection of remote evolutionary connections is increasingly difficult with sequence and structural divergence. A combination of sequence and structural analysis, in which statistically supported sequence similarity had a crucial impact, revealed that Escherichia coli topoisomerase I C-terminal fragment is evolutionarily related to the three tetracysteine zinc-binding domains of the enzyme. Spatial structure analysis of this C-terminal fragment indicates that it consists of two structurally similar domains and suggests homology between them. Sequence similarity between the zinc-binding domains of type Ia topoisomerases and transcription regulators of known spatial structure helps to conclude that E. coli topo I contains five copies of a zinc ribbon domain at the C terminus. Two of these domains, corresponding to the C-terminal fragment, lost their cysteine residues and are probably not able to bind zinc. Present analyses lead to the classification of the C-terminal fragment of E. coli topoisomerase I as a member of zinc ribbon superfamily, despite the absence of zinc-binding sites.

Amino Acid Sequence↗

PubMedDate not supplied

[The spatial organization of the EEG and individual psychological characteristics].

The influence of cognitive styles (analytic versus synthetic style, rigid versus flexible cognitive control, impulsivity versus reflexivity, field-dependence versus independence) on the information brain processes was estimated by means of analysis of spatial organization of cortical electrical activity (48 derivations) in 40 right-handed subjects (aged from 18 to 40) during their realization of verbal and non-verbal tasks using successive and simultaneous processing modes. Modulation of the "cognitive axis" (activity of the left anterior and right posterior cortical areas) was revealed connected with the factor of task subjective difficulty, especially in case of simultaneous processing mode. The combination of the synthetic cognitive style and flexibility of the cognitive control may be thought of as being the most favourable for the activation of the "cognitive axis" and utilization of the left- and right-hemispheric information processing, especially in non-standard situations.

Adolescent↗

PubMed1999

Population structure and gene flow of the brazilian shrub helicteres brevispira

Helicteres brevispira is a pioneer species of the tropical riparian forest whose populations appear to cycle through episodes of extinction and recolonization. Therefore, genetic consequences of founding events may strongly affect the genetic structure of its populations. An analysis of F-statistics showed that the studied population of H. brevispira is genetically substructured with the highest values of FST found in areas of high plant densities. Spatial autocorrelation analysis showed that genetic patches have diameters of 3-6 m. Although pollinator movements are usually between plants which are 3-6 m apart, longer flights occur and the neighbourhood area is estimated to have a diameter of 15 m. This suggests that genetic patches are smaller than the neighbourhood area. Seed dispersal is limited, mostly less than 2 m from the mother plants. Thus, short seed dispersal, seed dormancy and founder effects in the seed bank may be the most important determinants of genetic structure in populations of H. brevispira. Factors such as drift and inbreeding may also increase the level of substructure in this population, but the equilibrium model of isolation by distance does not fit our data.

Journal Article↗

PubMed2004

Environmental and social determinants of human risk during a West Nile virus outbreak in the greater Chicago area, 2002.

BACKGROUND: The outbreak of West Nile Virus (WNV) in and around Chicago in 2002 included over 680 cases of human illness caused by the virus within this region. The notable clustering of the cases in two well-defined areas suggests the existence of specific environmental and social factors that increase the risk for WNV infection and/or illness in these locations. This investigation sought to create an empirically based model to account for these factors and to assess their importance in explaining the possible processes that may have led to this pattern. RESULTS: The cluster pattern of high incidence of cases was statistically significant. The risk factors that were found to be important included the presence of vegetation, age, income, and race of the human population, distance to a WNV positive dead bird specimen, age of housing, mosquito abatement and geological factors. The effect of different mosquito abatement efforts was particularly notable. About 53 percent of the variation of the location of WNV clusters was explained by these factors. CONCLUSION: The models developed indicate that differential mosquito abatement efforts are especially important risk factors, even when controlling for key environmental factors. Human population characteristics play a role in risk that is measurable in this ecological study but would require further research to associate causality with risk. The analysis of spatial clusters of case incidence indicates that this approach provides more insight into the focal nature of differential risk factors that tend to be associated with WNV than an analysis of all individual cases.

Journal Article↗

PubMed2006

[Evaluation of visiting nursing care using geographical information system (GIS) technology].

PURPOSE: Previous evaluation studies of the visiting nursing program explained an average change of the participants' health status, without considering socio-ecological characteristics and their impacts. However, these factors must affect individual health problems and lifestyles. For effective and appropriate community based programs, the Geographical Information System (GIS) can be utilized. GIS is a computer-based tool for mapping and analyzing things that happen on earth, and integrates statistical analysis with unique visualization. The purpose of this study was to evaluate visiting nursing care and to advocate the usefulness of planning and evaluating visiting nursing programs using Exploratory Spatial Data Analysis (ESDA) with GIS technology. METHODS: One hundred eighty-four elderly participants with cerebrovascular risk factors who lived in 13 areas of one community received visiting nursing care. The data analyzed characteristics of pre-post change and autocorrelation by ESDA using GIS technology. RESULTS: Visiting nursing care showed an improvement in the participants' lifestyle habits, and family management ability and stress level, while the improvements were different depending on the regions. The change of family management ability and stress level correlated with neighborhoods (Morgan's I= 0.1841, 0.1675). CONCLUSIONS: Community health providers need to consider the individual participant's health status as well as socio-ecological factors. Analysis using GIS technology will contribute to the effective monitoring, evaluation and design of a visiting nursing program.

Aged↗

PubMed1993

Kin-structured migration and isolation by distance.

Classical isolation by distance models predict a negative exponential relationship between genetic similarity and geographic distance. Furthermore, under random spatial differentiation all alleles should reflect the same pattern because migration affects all loci identically. The effect of nonrandom composition of migrant groups (kin-structured migration) on these predictions was investigated using computer simulation. Spatial autocorrelation analysis of the simulated gene frequencies showed a decline in similarity with distance in the kin-structured experiments, as predicted by the isolation by distance model. However, the spatial autocorrelations were lower and the variation among correlograms of different alleles was greater than what would be expected under random migration. These findings suggest caution in inferring specific evolutionary conclusions from empirical spatial patterns.

Biological Evolution↗