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At least 847 records · Page 47Linked to original sources
PubMed2003

Spatial correlation of the infant and adult electroencephalogram.

OBJECTIVE: To examine the effects of volume conduction of current on measurements of spatial correlation in the high-density electroencephalogram (EEG) at extremes of human development: infancy and adulthood. METHODS: To calculate theoretical spatial correlation of EEG from volume conduction of uncorrelated cortical sources and compare theory with observations of intra/interhemispheric coherence. RESULTS: Result verified prediction of reduced spatial correlation in infants due to volume conduction. Theoretical magnitude of spatial correlation from volume conduction demonstrated as lower bound on observed magnitude of coherence (MC). MC of adults is greater than MC of infants. Adult intrahemispheric MC is greater than interhemispheric MC. Scalp muscle electromyogram (EMG) produces artifactually low values of MC. CONCLUSIONS: Volume conduction of current from uncorrelated cortical sources produces an erroneous component of spatial correlation that is smaller in infants than adults. The increased MC in adults is indicative of increased adult neuronal myelination. EMG artifact causes erroneous observations of coherence. SIGNIFICANCE: Measured EEG spatial correlation contains contributions from both neural activity and volume conduction of current. This is an important issue when measurements are used to deduce physiological correlates of neuropsychological phenomena. Measurements of the neural component of spatial correlation are more accurate early in life because of reduced volume conduction.

Adult↗
PubMed1999

Common spatial subspace decomposition applied to analysis of brain responses under multiple task conditions: a simulation study.

A method, called common spatial subspace decomposition, is presented which can extract signal components specific to one condition from multiple magnetoencephalography/electroencephalography data sets of multiple task conditions. Signal matrices or covariance matrices are decomposed using spatial factors common to multiple conditions. The spatial factors and corresponding spatial filters are then dissociated into specific and common parts, according to the common spatial subspace which exists among the data sets. Finally, the specific signal components are extracted using the corresponding spatial filters and spatial factors. The relationship between this decomposition and spatio-temporal source models is described in this paper. Computer simulations suggest that this method can facilitate the analysis of brain responses under multiple task conditions and merits further application.

Brain↗
PubMed1995

Reduced spatial learning in mice infected with the nematode, Heligmosomoides polygyrus.

Parasite modification of host behaviour influences a number of critical responses, but little is known about the effects on host spatial abilities. This study examined the effects of infection with the intestinal trichostrongylid nematode, Heligmosomoides polygyrus, on spatial water maze learning by male laboratory mice, Mus musculus. In this task individual mice had to learn the spatial location of a submerged hidden platform using extramaze visual cues. Determinations of spatial performance were made on day 19 post-infection with mice that had been administered either 50 or 200 infective larvae of H. polygyrus. The infected mice displayed over 1 day of testing (6 blocks of 4 trials) significantly poorer acquisition and retention of the water maze task than either sham-infected or control mice, with mice that had received 200 infective larvae displaying significantly poorer spatial performance than individuals receiving 50 larvae. The decrease in spatial learning occurred in the absence of either any symptoms of illness and malaise, or any evident motor, visual and motivational impairments. It is suggested that in this single host system the parasitic infection-induced decrease in spatial learning arises as a side-effect of the host's immunological and neuromodulatory responses and represents a fitness cost of response to infection.

Analysis of Variance↗
PubMedDate not supplied

Cooperative and competitive spatial interactions in motion integration.

Recovering the velocity of objects moving in the visual field requires both the integration and segmentation of local neuronal responses elicited by moving stimuli in primary visual cortex. Herein, we investigate the effects of the contrast, density, spatial proximity, spatial frequency, and spatial configuration of component motions on these complementary processes. Measuring the ability of human observers to discriminate the global direction of motion displays composed of spatially distributed patches of drifting gratings whose motion is locally ambiguous, we provide psychophysical evidence that linking component motion across space is facilitated at low contrast and high patch density. Furthermore, direction discrimination depends on the spatial frequency of component gratings and is more accurate for spatial configurations that contain "virtual" L junctions as compared to configurations composed of "virtual" T junctions. We suggest that the conditions yielding global motion coherence can be accounted for by the existence of anisotropic cooperative/competitive, contrast-dependent, long-range interactions among oriented direction-selective units. In addition, we bring evidence that motion segmentation processes rely upon the processing of moving local spatial discontinuities. The results are discussed in the light of recent psychophysical and physiological evidence that long-range excitatory and inhibitory interactions within primary visual cortex modulate perceptual linking.

Contrast Sensitivity↗
PubMed2002

Verbal and spatial working memory performance among HIV-infected adults.

Subtypes of working memory performance were examined in a cohort of 50 HIV-infected adults and 23 uninfected controls using an n-back paradigm (2-back) in which alphabetic stimuli were quasi-randomly presented to a quadrant of a computer monitor. In the verbal working memory condition, participants determined whether each successive letter matched the letter that appeared two previously in the series, regardless of spatial location. In the spatial working memory condition, participants determined whether each letter matched the spatial location of the letter that had appeared two previously, regardless of letter identity. The dependent variable was percent accuracy in each condition. Results of mixed model ANOVA revealed that the HIV-infected participants performed significantly worse than controls on both the verbal and spatial working memory tasks. A significant main effect for working memory condition was also present with both participant groups performing better on the spatial working memory task. These results, the first study of HIV-infected adults to directly compare verbal versus spatial working memory performance using the identical test stimuli across task conditions, suggests that HIV infection is associated with a decrement in working memory efficiency that is equally apparent for both verbal and spatial processing. These findings implicate central executive dysfunction as a likely substrate and provide the basis for hypothesizing that decline in working memory may contribute to other HIV-associated neuropsychological deficits.

Adult↗
PubMed2002

Risk based management of contaminated sediments: consideration of spatial and temporal patterns in exposure modeling.

This paper addresses interactions among foraging behavior, habitat preferences, site characteristics, and spatial distribution of contaminants in developing PCB exposure estimates for winter flounder at a hypothetical open water dredged material disposal site in the coastal waters of New York and New Jersey (NY-NJ). The implications of these interactions for human health risk estimates for local recreational anglers who fish for and eat flounder are described. The models implemented in this study include a spatial submodel to account for spatial and temporal characteristics of fish exposures and a probabilistic adaptation of the Gobas bioaccumulation model that accounts for temporal variation in concentrations of hydrophobic contaminants in sediment and water. We estimated the geographic distribution of a winter flounder subpopulation offshore of NY-NJ based on species biology and its vulnerability to local recreational fishing, the foraging area of individual fish, and their migration patterns. We incorporated these parameters and an estimate of differential attraction to a management site into a spatially explicit model to assess the range of exposures within the population. The output of this modeling effort, flounder PCB tissue concentrations, provided exposure point concentrations for an estimate of human health risk through ingestion of locally caught flounder. The risks obtained for the spatially nonexplicit case are as much as 1 order of magnitude higher than those obtained with explicit consideration of spatial and temporal characteristics of winter flounder foraging and seasonal migration. This practice of "defaulting" to extremely conservative estimates for exposure parameters in the face of uncertainty ill serves the decision-making process for management of contaminated sediments in general and specifically for disposal of dredged materials. Consideration of realistic spatial and temporal scales in food chain models can help support sediment management decisions by providing a quantitative expression of the confidence in risk estimates.

Animals↗
PubMed1996

The separability of working memory resources for spatial thinking and language processing: an individual differences approach.

The current study demonstrates the separability of spatial and verbal working memory resources among college students. In Experiment 1, we developed a spatial span task that taxes both the processing and storage components of spatial working memory. This measure correlates with spatial ability (spatial visualization) measures, but not with verbal ability measures. In contrast, the reading span test, a common test of verbal working memory, correlates with verbal ability measures, but not with spatial ability measures. Experiment 2, which uses an interference paradigm to cross the processing and storage demands of span tasks, replicates this dissociation and further demonstrates that both the processing and storage components of working memory tasks are important for predicting performance on spatial thinking and language processing tasks.

Adult↗
PubMed1979

Spatial contiguity facilitates Pavlovian second-order conditioning.

Two experiments investigated the effects of spatial contiguity upon the formation of second-order conditioning in pigeon subjects. Experiment 1 used an autoshaping procedure to pair two visual stimuli, S2 and S1, after S1 had previously been paired with food. The resulting second-order conditioning of S2 was superior when both stimuli appeared on the same response key within a trial, compared with their appearing on different keys. Experiment 2 found a similar importance of spatial contiguity between S2 and S1 in a conditioned suppression paradigm. In addition, consistently presenting S2 and S1 in the same spatial location produced superior conditioning compared with varying their spatial relation from trial to trial. The design of these experiments was such as to imply that spatial contiguity facilitates performance by improving the formation of association rather than by promoting stimulus generalization or pseudoconditioning. Moreover, the observation of a facilitative effect of spatial contiguity between S1 and S2 in two different paradigms that use qualitatively different unconditioned stimuli and evoke different responses implies some generality for these findings. Consequently, these results suggest that spatially contiguous stimuli are especially associable in Pavlovian conditioning paradigms.

Animals↗
PubMed2000

The role of stimulus-based and response-based spatial information in sequence learning.

In 4 experiments, relational structures were independently varied in stimulus and response sequences in a serial reaction time task. Moreover, the use of spatial and symbolic stimuli and responses was varied between experiments. In Experiment 1, spatial stimuli (asterisk locations) triggered spatial responses (keystrokes); in Experiment 2, spatial stimuli triggered symbolic responses (verbal digit naming); in Experiment 3, symbolic stimuli (digits) triggered keystrokes; and in Experiment 4, digits triggered verbal responses. The results showed that there is a remarkably stronger effect of relational structures in spatial sequences than in symbolic sequences, irrespective of whether stimulus or response sequences are concerned. This suggests that learning is particularly effective for sequences of spatial locations. It is argued that spatial learning is a critical determinant for the debate on perceptual and motor learning.

Adult↗
PubMed2000

Individual differences in spatial learning from computer-simulated environments.

A multivariate study examined relationships between the following factors: paper-and-pencil assessments of verbal and spatial ability, ability to form an accurate spatial representation of a large real-world environment, gender, computer attitudes and experience, proficiency with the navigational interface of a virtual environment (VE), and the ability to acquire and transfer spatial knowledge from a VE. Psychometrically assessed spatial ability and proficiency with the navigational interface were found to make substantial contributions to individual differences in the ability to acquire spatial information from a VE. Gender influenced many VE-related tasks, primarily through its relationship with interface proficiency and spatial ability. Measures of spatial knowledge of a VE maze were highly predictive of subsequent performance in a similar real-world maze, suggesting that VEs can be useful for training people about real-world spaces.

Adult↗
PubMed2000

Spatial encoding of hidden objects in dogs (Canis familiaris).

The authors investigated the type of spatial information that controls domestic dogs' (Canis familiaris) search behavior in a situation in which they have to locate a spatial position where they saw an object move and disappear. In Experiments 1 and 2, the authors manipulated all local and global sources of allocentric spatial information surrounding the hiding location. The results revealed that dogs relied on an egocentric frame of reference. Experiment 3 showed that dogs also encoded allocentric information when egocentric information was irrelevant. The authors conclude that dogs simultaneously encode both egocentric and allocentric spatial information to locate a spatial position, but they primarily base their search behavior on an egocentric frame of reference. The authors discuss under which natural conditions dogs might use these 2 sources of spatial information and detail the nature of spatial egocentric information and the circumstances underlying its use by dogs.

Animals↗
PubMed2004

Recalling spatial information as a component of recently and remotely acquired episodic or semantic memories: an fMRI study.

Activations produced by the recall of episodic and semantic memories differing in spatial content and age were examined. Recall of recent episodic memories with differing spatial content activated the medial temporal lobes and the retrosplenial-posterior cingulate cortex-precuneus complex more than recall of recent semantic memories with similarly differing spatial content. Some of these differences related to the amount of spatial information recalled because spatially richer recent memories, regardless of whether they were episodic or semantic, activated the right posterior parahippocampal cortex, precuneus, and posterior parietal cortex more. This spatial effect was found to be independent of memory age for semantic memories, although some episodic-semantic memory differences, including one in the left hippocampus, were not age independent. Episodic-semantic memory recall activation differences are therefore probably a function of the amount recalled, memory age, and what is recalled, particularly with respect to spatial information.

Adult↗
PubMed1994

Broad tuning for spatial frequency of neural mechanisms underlying visual perception of coherent motion.

Neural events underlying perception of coherent motion are generally believed to be hierarchical: information about local motion is registered by spatio-temporal coincidence detectors whose outputs are cooperatively integrated at a subsequent stage. There is disagreement, however, concerning the spatial scale of the neural filters underlying these operations. According to one class of models, motion registration is initially accomplished in parallel at multiple spatial scales, with filters tuned to lower spatial frequencies responsive to larger motion displacements than filters tuned to higher frequencies. According to another scheme, motion analysis involves a single, broadly tuned spatial filter, with optimal displacement dependent on spacing of local elements. Here we use a masking procedure to measure the extent to which dynamic noise depicted at one spatial scale interferes with detection of coherent motion conveyed by image features at another spatial scale. Our results indicate that a single filter, broadly tuned for spatial frequency, is mediating detection of coherent motion. This finding dovetails with known physiological properties of neurons at an intermediate stage of motion processing.

Fourier Analysis↗
PubMed2025

Giotto Suite: a multiscale and technology-agnostic spatial multiomics analysis ecosystem.

Emerging spatial multiomics technologies provide an increasingly large amount of information content at multiple scales. However, it remains challenging to efficiently represent and harmonize diverse spatial datasets. Here we present Giotto Suite, a suite of modular packages that provides scalable and extensible end-to-end solutions for multiscale and multiomic data analysis, integration and visualization. At its core, Giotto Suite is centered around an innovative data framework, allowing the representation and integration of spatial omics data in a technology-agnostic manner. Giotto Suite integrates molecular, morphology, spatial and annotated feature information to create a responsive and flexible workflow, as demonstrated by applications to several state-of-the-art spatial technologies. Furthermore, Giotto Suite builds upon interoperable interfaces and data structures that bridge the established fields of genomics and spatial data science in R, thereby enabling independent developers to create custom-engineered pipelines. As such, Giotto Suite creates an immersive and multiscale ecosystem for spatial multiomic data analysis.

Genomics↗
PubMed2026

Spatial mapping of RNA turnover kinetics in the mouse brain.

Gene regulation requires coordinated control of RNA synthesis and degradation, yet measuring RNA turnover across intact tissues remains challenging. Here we present spatial NT-seq, a method that combines transgenesis-free metabolic RNA labeling with in situ chemical recoding on spatial transcriptomics platforms to co-map newly synthesized and pre-existing RNAs. Applying spatial NT-seq to the mouse brain reveals pronounced regional heterogeneity in RNA turnover and identifies the dentate gyrus as a spatial hotspot marked by coordinated upregulation of basal RNA synthesis and decay. Moreover, spatial NT-seq uncovers rapid, brain region-specific transcriptional and post-transcriptional responses to electroconvulsive stimulation, a clinically relevant treatment for refractory depression. Finally, we leverage computational modeling to identify sequence features and post-transcriptional regulators that shape transcriptome-wide mRNA stability across spatial and cellular contexts in the mouse brain. Together, this integrated 'in vivo timescope' framework provides a spatially resolved view of RNA turnover kinetics and reveals the regulatory architecture of RNA stability in vivo.

Journal Article↗
PubMed2005

Spatial genetic structure of two sympatric neotropical palms with contrasting life histories.

The spatial genetic structure within sympatric populations of two neotropical dioecious palm species with contrasting life histories was characterized to evaluate the influence of life history traits on the extent of genetic isolation by distance. Chamaedorea tepejilote is a common wind-pollinated arboreal understory palm. Chamaedorea elatior is an uncommon climbing subcanopy palm with entomophilous pollination syndrome. A total of 59 allozyme alleles for C. tepejilote and 53 alleles for C. elatior was analyzed using both unweighted (Iu) and weighted (Iw) Moran's I spatial autocorrelation statistics. The spatial genetic structure detected within these populations is consistent with those reported for highly dispersed plants. A significance test for differences between mean Moran's I-coefficients revealed less spatial genetic structure within the C. tepejilote population than that in the C. elatior population. Adjacent individuals of C. elatior exhibited significant spatial genetic autocorrelation (Iu=0.039, Iw=0.034), indicating a Wright's neighborhood size of about 100 individuals. For C. tepejilote, nonrandom genetic distribution among nearest neighbors was detected, even from small spatial autocorrelation values (Iu=0.008, Iw=0.009), consistent with a neighborhood size of about 300 individuals. For both species, seed dispersal, mortality among life cycle stages, overlapping generations, and contrasting traits of mating and reproduction influence the standing spatial genetic structure within populations.

Arecaceae↗
PubMed2001

The spatial QRS-T angle as a marker of ventricular repolarisation in hypertension.

Ventricular repolarisation abnormalities are important in arrhythmia provocation. The dispersion of repolarisation duration is not the only aspect of repolarisation heterogeneity. Spatial vectorcardiographic descriptors constitute a novel approach to quantify ventricular repolarisation. To test the ability of vectorcardiographic descriptors to discriminate between hypertensives with high or low blood pressure (BP), 110 treated hypertensives (mean age 63.6 +/- 12.1 years) were classified in the high (systolic BP > or = 160 mm Hg or diastolic BP > or = 95 mm Hg) (n = 67), or the low (systolic BP < 160 mm Hg and diastolic BP <95 mm Hg) (n = 43) BP group. The maximum QT, JT, and T peak-T end intervals and the QT, JT, and T peak--T end dispersion were calculated from a digitally recorded 12-lead electrocardiogram (ECG). X, Y, and Z leads were reconstructed from the 12-lead ECG. The amplitude of the maximum spatial T vector (spatial T amplitude), the angle between the maximum spatial QRS and T vectors (spatial QRS-T angle) and the frontal plane QRS-T angle were calculated. The spatial QRS-T angle was higher in patients with high compared to those with low BP (P = 0.025). All conventional ECG markers of the dispersion of ventricular repolarisation duration failed to demonstrate significant differences between hypertensives with high or low BP. In conclusion, the spatial QRS-T angle was significantly increased in those treated hypertensive patients who showed repeatedly high BP values. Hence, we may suggest that the angle between the directions of ventricular depolarisation and repolarisation is a sensitive marker of the repolarisation alterations in systemic hypertension. Journal of Human Hypertension (2001) 15, 63-70

Aged↗
PubMed2003

Phosphatidylinositol 3-kinase: a molecule mediating BDNF-dependent spatial memory formation.

Brain-derived neurotrophic factor (BDNF) plays a critical role in synaptic plasticity such as long-term potentiation (LTP), a form of synaptic correlate of learning and memory. BDNF is also implicated in learning and memory. We have demonstrated that radial arm maze training in rats for spatial learning and memory results in a significant increase in the BDNF mRNA expression in the hippocampus. Moreover, antisense BDNF oligonucleotide treatment impaired not only acquisition, but also maintenance and/or recall of spatial memory in the maze. Although these results suggest a role of BDNF for spatial memory processes, the signal transduction mechanisms that mediate the actions of BDNF remain unknown. Here we show that phosphorylation of BDNF receptor tyrosine kinase B (TrkB), phosphatidylinositol 3-kinase (PI3-K) and Akt, a target of PI3-K, in the hippocampus increased in parallel with spatial memory formation. Moreover, an activation of translational processes was suggested in the hippocampus after the maze training. When spatial learning was inhibited by antisense BDNF oligodeoxynucleotide, the activation was diminished. Chronic treatment with PI3-K inhibitor wortmannin impaired spatial learning. Our findings suggested that activation of TrkB/PI3-K and protein synthesis signaling pathway by BDNF in the hippocampus is important for spatial memory.

Androstadienes↗