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PubMed2002

Spatial filtering using a raster geographic information system: methods for scaling health and environmental data.

Despite the use of geographic information systems (GIS) in academic research, it is still uncommon for public health officials to use such tools for addressing health and environmental issues. Complexities in methodological issues for addressing relationships between health and environment, investigating spatial variation of disease, and addressing spatial demand and supply of health care service, hinder the use of GIS in the health sector. This paper demonstrates simple spatial filtering methods for analyzing health and environmental data using a raster GIS. Computing spatial moving average rates reduces individual affects and creates a continuous surface of phenomena. Another spatial analytical method discussed is computation of exposure status surfaces including neighbors' influences weighted by distance decay. These methods describe how health and environmental data can be scaled in order to better address health problems. Spatial filtering methods are demonstrated using health and population surveillance data within a GIS that were collected for approximately 210,000 people in Matlab, Bangladesh.

Bangladesh↗
PubMed2000

Spatial structuring and frequency distribution of the nematode Steinernema feltiae Filipjev.

The frequency distribution of first generation, Steinernema feltiae Filipjev parasitic stages was over-dispersed with the majority of hosts containing few or no parasitic stages, whilst a few hosts contained a great many. Because of high extraction efficiency, the frequency distributions of the parasitic stages and the infective stages in the soil were assumed to be directly related. To explain the frequency distribution of the parasites it was therefore necessary to account for the frequency distribution of the S. feltiae infective stages in the soil. The infective stages were spatially aggregated into 30 cm diameter patches at the site of host death. These patches were randomly distributed approximately 1 m apart. At the 1 m scale, the pooled counts of infective stages were randomly distributed. Thus, in contrast to the frequency distributions, the spatial structuring of S. feltiae changed with the spatial scale of the interaction. This dynamic spatial structuring means that the majority of samples taken would contain few or no infective stages, whilst a few soil samples would contain a great many. Thus, the spatial structuring of the infective stages generates the over-dispersed frequency distribution of the S. feltiae in the soil. Hosts, encountering infective stages from this spatial distribution will, therefore, show an over-dispersed frequency distribution of S. feltiae parasitic stages.

Animals↗
PubMed2004

Spatial analysis of the distribution of intestinal nematode infections in Uganda.

The spatial epidemiology of intestinal nematodes in Uganda was investigated using generalized additive models and geostatistical methods. The prevalence of Ascaris lumbricoides and Trichuris trichiura was unevenly distributed in the country with prevalence greatest in southwest Uganda whereas hookworm was more homogeneously distributed. A. lumbricoides and T. Trichiura prevalence were nonlinearly related to satellite sensor-based estimates of land surface temperature; hookworm was nonlinearly associated with rainfall. Semivariogram analysis indicated that T. trichiura prevalence exhibited no spatial structure and that A. lumbricoides exhibited some spatial dependency at small spatial distances, once large-scale, mainly environmental, trends had been removed. In contrast, there was much more spatial structure in hookworm prevalence although the underlying factors are at present unclear. The implications of the results are discussed in relation to parasite spatial epidemiology and the prediction of infection distributions.

Adolescent↗
PubMed1990

Spatial and temporal analysis by neurons in the representation of the central visual field in the cat's lateral suprasylvian visual cortex.

We studied quantitatively the receptive-field properties of 74 units recorded from the representation of the central visual fields in the cat's lateral suprasylvian (LS) visual cortex. In agreement with previous workers, we found that LS receptive fields tended to be large and to lack discernible spatial structure. They resembled the complex receptive fields of areas 17 and 18 in their general organization. We examined the responses of these neurons to moving optimally oriented sinusoidal gratings that varied in spatial and temporal frequency of drift. Most LS neurons were selective for the spatial frequency of sinusoidal gratings; 7% responded to all spatial frequencies below a cutoff value. In agreement with previous reports, the optimal spatial frequencies for LS neurons covered a wider range than is seen in either area 17 or 18 alone (0.05-1 cycle/deg), but are certainly included in the range covered by both these afferent areas. Individual neurons in LS responded to a range of spatial frequencies broader than is typical for neurons in areas 17 and 18. The effect of varying the drift rate of otherwise optimal gratings was similar in LS to that reported for areas 17 and 18. Most neurons were optimally responsive to drift rates between 0.5 and 4 Hz, and resolved frequencies as high as 10-30 Hz. A few neurons had optima higher than 6 Hz and resolved frequencies in excess of 30 Hz. We conclude that the receptive fields of LS neurons reflect rather closely the properties of their afferents from areas 17 and 18.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

Spatial but not verbal cognitive deficits at age 3 years in persistently antisocial individuals.

Previous studies have repeatedly shown verbal intelligence deficits in adolescent antisocial individuals, but it is not known whether these deficits are in place prior to kindergarten or, alternatively, whether they are acquired throughout childhood. This study assesses whether cognitive deficits occur as early as age 3 years and whether they are specific to persistently antisocial individuals. Verbal and spatial abilities were assessed at ages 3 and 11 years in 330 male and female children, while antisocial behavior was assessed at ages 8 and 17 years. Persistently antisocial individuals (N = 47) had spatial deficits in the absence of verbal deficits at age 3 years compared to comparisons (N = 133), and also spatial and verbal deficits at age 11 years. Age 3 spatial deficits were independent of social adversity, early hyperactivity, poor test motivation, poor test comprehension, and social discomfort during testing, and they were found in females as well as males. Findings suggest that early spatial deficits contribute to persistent antisocial behavior whereas verbal deficits are developmentally acquired. An early-starter model is proposed whereby early spatial impairments interfere with early bonding and attachment, reflect disrupted right hemisphere affect regulation and expression, and predispose to later persistent antisocial behavior.

Adolescent↗
PubMed1995

Memory for novel and familiar spatial and linguistic temporal distance information in hypoxic subjects.

Hypoxia is known to cause damage to the hippocampus as well as memory impairments in humans. Subjects who have experienced a hypoxic episode and age-, gender-, and education-matched control subjects were tested for memory for spatial and linguistic temporal distance information using sentences and spatial locations. Each test contained a familiar component based on information that is meaningful and is thought to be stored as part of the knowledge system (prior knowledge) as well as a novel component based on new information. Subjects were presented a list of eight-word sentences or eight spatial locations (Xs) on a grid on a Macintosh computer and tested for memory for temporal distances. Temporal distance is defined as the number of items that occur between the two test items, in the study phase. Compared to control subjects, hypoxic subjects were impaired across all temporal distances on the novel spatial and linguistic tasks. As the temporal distance increased, hypoxic subjects showed some improvement in memory performance. In addition, memory of familiar temporal distance information was also assessed. Hypoxic subjects were impaired, compared to control subjects, for familiar temporal distance information. For hypoxic subjects there was a proportionally greater impairment for novel compared to familiar spatial and linguistic temporal distance information. There was a significant difference in their performance on the familiar temporal distance tasks compared to their performance on the novel tasks. Prior knowledge appears to attenuate the deficits seen in the familiar temporal distance tasks. It appears that hypoxia may cause more selective damage to the hippocampus and this damage is sufficient to produce profound memory impairments for primarily novel and less severe memory impairments for familiar spatial and linguistic temporal distance information.

Adult↗
PubMed2006

Spatial and temporal order memory in Korsakoff patients.

This study directly compared how well Korsakoff patients can process spatial and temporal order information in memory under conditions that included presentation of only a single feature (i.e., temporal or spatial information), combined spatiotemporal presentation, and combined spatiotemporal order recall. Korsakoff patients were found to suffer comparable spatial and temporal order recall deficits. Of interest, recall of a single feature was the same when only spatial or temporal information was presented compared to conditions that included combined spatiotemporal, presentation and recall. In contrast, control participants performed worse when they have to recall both spatial and temporal order compared to when they have to recall only one of these features. These findings together indicate that spatial and temporal information are not automatically integrated. Korsakoff patients have profound problems in coding the feature at hand. Moreover, their lower recall of both features at the same time suggests that Korsakoff patients are impaired in binding different contextual attributes together in memory.

Adult↗
PubMed2005

Caffeine improves spatial learning deficits in an animal model of attention deficit hyperactivity disorder (ADHD) -- the spontaneously hypertensive rat (SHR).

The spontaneously hypertensive rat (SHR) is generally considered to be a suitable genetic model for the study of attention deficit hyperactivity disorder (ADHD), since it displays hyperactivity, impulsivity, poorly sustained attention, and deficits in learning and memory processes. Converging evidence suggests a primary role of disturbance in the dopaminergic neurotransmission in ADHD patients and in SHR, and in addition, some studies have also demonstrated alterations in adenosinergic neurotransmission in SHR. In the present study, adult female Wistar (WIS) and SHR rats received caffeine (1-10 mg/kg i.p.) 30 min before training, immediately after training, or 30 min before a test session in the spatial version of the Morris water maze. The effect of caffeine administration on WIS and SHR blood pressure was also measured. SHR needed significantly more trials in the training session to acquire the spatial information, but they displayed a similar profile to that of WIS rats in the test session (48 h later), demonstrating a selective deficit in spatial learning. Pre-training administration of caffeine (1-10 mg/kg i.p.) improved this spatial learning deficit in SHR, but did not alter the WIS performance. In contrast, post-training administration of caffeine (3 mg/kg i.p.) did not alter the SHR test performance, but increased memory retention in WIS rats. No dose of caffeine tested altered the mean blood pressure of WIS or SHR. These results demonstrate a selective spatial learning deficit in SHR which can be attenuated by pre-training administration of caffeine. In addition, the present findings indicate that the spatial learning deficit in SHR is not directly related to hypertension.

Animals↗
PubMed2005

Multimedia fate and human intake modeling: spatial versus nonspatial insights for chemical emissions in Western Europe.

Multimedia fate and multipathway human exposure models are widely adopted in assessments of toxicological risks of chemical emissions at the regional scale. This paper addresses the question of how much spatial detail is necessary in such models when estimating the intake by the entire population in large, heterogeneous regions such as Europe. The paper presents a spatially resolved multimedia fate and multipathway exposure model for Western Europe, available as IMPACT 2002. This model accounts for relationships between the location of food production and drinking water extraction as well as where population cohorts live relative to where chemical emissions occur. The model facilitates estimation of environmental concentration distributions, related levels of contaminants in foods, and the fraction of a chemical release that will be taken in by the entire human population (the intake fraction) at the regional scale. To evaluate the necessary spatial resolution, the paper compares estimates of environmental concentrations and the intake fraction from the spatially resolved model with the results of a consistent clone without spatial resolution. An evaluation for disperse emissions of PeCDF (2,3,4,7,8-pentachlorodibenzofuran, CAS# 5120731-4) suggests reasonable agreement with monitoring data for most impact pathways with both versions of the model, but that the generic vegetation models for estimating contaminant concentrations in agricultural produce require improvement. A broader comparison for a range of organic chemicals demonstrates that the nonspatial models are likely to be appropriate in general for assessing dispersed sources of emissions. However, it is necessary to include generic compartments in such nonspatial models to account separately for emissions that enter lakes with long residence times versus rivers that feed directly into seas. For assessing an emission source in a specific location, using models that are not spatially resolved can result in underestimation, or overestimation, of the population's intake by at least 3 orders of magnitude for some chemicals.

Benzofurans↗
PubMed1999

Spatial autocorrelation of cancer in Western Europe.

We applied the techniques of spatial autocorrelation (SA) analysis to 40 cancer mortality distributions in Western Europe. One of the aims of these methods is to describe the scale over which spatial patterns of mortalities occur, which may provide suggestions concerning the agents bringing about the patterns. We analyzed 355 registration areas, applying one- and two-dimensional SA as well as local SA techniques. We find that cancer mortalities are unusually strongly spatially structured, implying similar spatial structuring of the responsible agents. The small number of spatial patterns (4 or 5) in the 40 cancer mortalities suggests there are fewer spatially patterned agents than the number of cancers studied. SA present in variables will bias the results of conventional statistical tests applied to them. After correcting for such bias, some pairwise correlations of cancer mortality distributions remain significant, suggesting inherent, epidemiologically meaningful correlations. Local SA is a useful technique for exploring epidemiological maps. It found homogeneous high overall cancer mortalities in Denmark and homogeneous low mortalities in southern Italy, as well as a very heterogeneous pattern for ovarian cancer in Ireland.

Cluster Analysis↗
PubMed2003

Analysis of fMRI data by blind separation of data in a tiny spatial domain into independent temporal component.

Independent Component Analysis (ICA) is a promising tool for the analysis of functional magnetic resonance imaging (fMRI) time series. In these studies, mostly assumed is a spatially independent component map of fMRI data (spatial ICA). In this paper, we assume that the temporal courses of the signal and noises are independent within a Tiny spatial domain (temporal ICA). Then with fast-ICA algorithm, spatially neighboring fMRI data were blindly separated into several temporal courses and were preassumed to be formed by a signal time course and several noise time courses where the signal has the largest correlation coefficient with the reference signal. The final functional imaging was completed for the signals obtained from each voxel. Simulations showed that compared with the spatial ICA method, the new temporal ICA method is more effective than the spatial ICA in detecting weak signal in a fMRI dataset. As background noise, the simulations include simulated Gaussian noise and fMRI data without stimulation. Finally, vivo fMRI tests showed that the excited areas evoked by a visual stimuli are mainly in the region of the primary visual cortex and that evoked by auditory stimuli are mainly in the region of the primary temporal cortex.

Algorithms↗
PubMedDate not supplied

A study on the spatial distribution of nitrogen and phosphorus balance, and regional nitrogen flow through crop production.

The spatial distribution patterns of the nitrogen and phosphorus input/intake amounts in crop production within two small basins are examined, based upon a cropping unit distribution map that is obtained from remote sensing data analysis. Firstly, we examine the availability and suitability of approaches to the spatial distribution analysis of cultivation patterns classified from material flow characteristics of crop production using seasonal remote-sensing data. Secondly, material flow units in crop production are grouped according to the cultivation patterns obtained from the remote-sensing data analysis. Consequently, the spatial patterns of the amounts of both nitrogen and phosphorus inputs/intakes through crop production on farmland are examined and their spatial distribution maps are prepared according to the material flow units. In addition, we developed a nitrogen flow and runoff model and the model is simulated based on the examination of the results of spatial distribution patterns of the material flow units. The annual nitrogen runoff from small catchments, where various crops are cultivated, varies from 2.7 kg ha(-1) year(-1) to 108 kg ha(-1) year(-1) and the annual balanced losses of nitrogen in small catchments varied from -30 kg ha(-1) year(-1) to 101 kg ha(-1) year(-1). Also, the monthly changes in soil nitrogen of each material flow unit is estimated at -55 kg ha(-1) as a maximum decrease and 114 kg ha(-1) as a maximum increase. These results indicate that the spatial distribution patterns of nutrient input and intake through agricultural activities should be considered when analyzing the material flows and nutritient movement in soil-water systems in rural areas for watershed environmental control and regional agricultural management.

Agriculture↗
PubMed2002

Spatial frequency discrimination in schizophrenia.

Pathways within the visual system can be distinguished on the basis of selectivity for low or high spatial frequencies. Spatial frequency discrimination was evaluated in 17 medicated male patients with schizophrenia and 19 male control subjects. Subjects were required to discriminate whether pairs of high contrast, sinusoidally modulated gratings were the same or different in spatial frequency. Accuracy performance was compared at high, medium, and low spatial frequencies on tasks matched for control performance. Patients showed a greater performance decrement of 12% on low as compared with 4% on high spatial frequencies. These findings suggest a disturbance of right hemisphere mechanisms involved in spatial perception and attention in schizophrenia.

Adult↗
PubMed1996

Spatial patterns in the control of human arm movement.

Generalized Procrustes analysis was used to investigate the spatial paths of pointing movements. In Experiment 1, 3 participants produced similar spatial paths of the hand when repeating a pointing movement many times, despite variability in the position and orientation of the movements. The average spatial path indicates a fundamental spatial pattern of the motor system, or motor primitive. This pattern varied across the workspace. Anterioposterior movements were straight, but repeated movements had variable spatial patterns. Lateral movements were curved away from the body but had regular spatial patterns. Experiment 2 extended these results to movements of different amplitudes in 7 participants. The motor primitive seems to be abandoned at the end of the movement in favor of final adjustments to bring the hand to the target position. In Experiment 3, the same participants produced similar motor primitives both with and without vision.

Arm↗
PubMed1988

The acquisition of task-specific productions and modifications of declarative representations in spatial-precuing tasks.

The stimulus-response translation stage of human information processing plays a mediating role of relating stimuli to assigned responses. The translation stage has been implicated as the locus of a pattern of differential precuing benefits obtained in spatial-choice tasks (Proctor & Reeve, 1986; Reeve & Proctor, 1985): When pairs of finger responses from the middle and index fingers of each hand are precued, the two leftmost and two rightmost responses show the greatest benefit. This pattern of differential benefits, which occurs regardless of whether the hand placement is adjacent or overlapped, has been attributed to spatially coded representations of the stimulus and response sets in the translation stage. Experiment 1 evaluated whether the mediating role of the translation stage changes with practice. All precued pairs of responses showed equivalent benefits in the last of three sessions. This result indicates that the spatial representations used initially to translate between stimuli and responses have been altered to be more efficient or have been replaced by productions that directly specify fingers. Experiment 2 used a fourth session in which subjects were transferred from the overlapped hand placement to the adjacent placement, or vice versa. For subjects in the former condition, the pattern of differential precuing benefits reappeared in the transfer session. This lack of transfer is consistent with the hypothesis that task-specific productions develop with practice that directly relate stimuli to fingers. For subjects who practiced with the adjacent placement and switched to the overlapped placement, only a nonsignificant tendency existed for the pattern of differential precuing benefits to reappear. This failure of the pattern to reappear could indicate that spatial representations continue to be used to translate between stimuli and responses. Alternatively, as occurs with the overlapped placement, task-specific productions could be acquired that relate stimuli to fingers. If so, the failure of the pattern of differential precuing benefits to reappear would reflect a modification in the representations that are used for translation in the transfer session. Specifically, if subjects were coding the stimulus and response sets on the basis of the distinction between the two hands, as well as the spatial distinction, the differential benefits would be minimized because hand coding should benefit different responses from those benefitted by spatial coding. These alternative explanations were evaluated in Experiment 3 by having subjects who practiced with the adjacent placement switch to a placement in which the hands were crossed completely.(ABSTRACT TRUNCATED AT 400 WORDS)

Cues↗
PubMed1989

Subjective hierarchies in spatial memory.

Two experiments investigated the structure of spatial memories. Subjects learned locations of objects in spatial layouts (Experiment 1) or locations of object names on maps (Experiment 2). Physical and perceptual boundaries were absent in these spatial arrays. Subjects then participated in three tasks: item recognition, in which the variable of interest was spatial priming; free and cued recall; and Euclidean distance estimation. Ordered-tree analysis of individual subjects' recall protocols produced hierarchical trees consistent with regularities in output order. Spatial priming and distance estimations depended on whether pairs of objects appeared in the same subtree or in different subtrees. These findings indicate that spatial memories have a hierarchical component, even when physical and perceptual boundaries are nonexistent. Priming also increased with depth of clustering in ordered trees. This result supports spreading-activation theories of retrieval but provides evidence against several "non-spreading-activation" theories.

Adult↗
PubMed1989

Orientation specificity in spatial memory: what makes a path different from a map of the path?

Three studies investigated the factors that lead spatial information to be stored in an orientation-specific versus orientation-free manner. In Experiment 1, we replicated the findings of Presson and Hazelrigg (1984) that learning paths from a small map versus learning the paths directly from viewing a world leads to different functional characteristics of spatial memory. Whether the route display was presented as the path itself or as a large map of the path did not affect how the information was stored. In Experiment 2, we examined the effects of size of stimulus display, size of world, and scale transformations on how spatial information in maps is stored and available for use in later judgments. In Experiment 3, we examined the effect of size on the orientation specificity of the spatial coding of paths that are viewed directly. The major determinant of whether spatial information was stored and used in an orientation-specific or an orientation-free manner was the size of the display. Small displays were coded in an orientation-specific way, whereas very large displays were coded in a more orientation-free manner. These data support the view that there are distinct spatial representations, one more perceptual and episodic and one more integrated and model-like, that have developed to meet different demands faced by mobile organisms.

Adult↗
PubMed2000

Functional characteristics of auditory temporal-spatial short-term memory: evidence from serial order errors.

The functional characteristics of auditory temporal-spatial short-term memory were explored in 8 experiments in which the to-be-remembered stimuli were sequences of bursts of white noise presented in spatial locations separated in azimuth. Primacy and recency effects were observed in all experiments. A 10-s delay impaired recall for primacy and middle list items but not recency. This effect was shown not to depend on the response modality or on the incidence of omissions or repetitions. Verbal and nonverbal secondary tasks did not affect memory for auditory spatial sounds. Temporal errors rather than spatial errors predominated, suggesting that participants were engaged in a process of maintaining order. This pattern of results may reflect characteristics that serial recall has in common with verbal and spatial recall, but some are unique to the representation of memory for temporal-spatial auditory events.

Attention↗