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At least 631 records · Page 35Linked to original sources
PubMed2000

Spatial complexity in children's language.

The purpose of this research was to explore the properties of locative scenes which influence the sequence of the acquisition of spatial prepositions in English. Children ranging in age from about 2;8 to 5;6 were tested with a comprehension test involving a sentence-picture matching task. The comprehension test contained six kinds of spatial contrasts which were judged to vary in the geometric complexity of the scene. The order of acquisition was as follows: (1) into/out of & onto/off of, (2) in/on, (3) into/onto & out of/off of and through/over (around), (4) between X & Y/Y & Z, and (5) across/along. Complexity depends on a number of factors such as the number of referent objects and the nature of the relationship between the object to be located and the critical feature of the referent object. Prepositions which involve a more complex spatial geometry are more difficult for young children to comprehend. It was argued that the sequence of acquisition is partially determined by the course of conceptual development.

Child, Preschool↗
PubMed1995

Functional equivalence of verbal and spatial information in serial short-term memory.

Performance on a test of serial memory for the spatial position of a sequence of dots showed similarities to typical results from the serial recall of verbal material: a marked increase in error with increasing list length, a modest rise in error as retention interval increased, and bow-shaped serial position curves. This task was susceptible to interference from both a spatial task (rote tapping) and a verbal task (mouthed articulatory suppression) and also from the presence of irrelevant speech. Effects were comparable to those found with a serial verbal task that was generally similar in demand characteristics to the spatial task. As a generalization, disruption of the serial recall of visuospatial material was more marked if the interference conditions involved a changing sequence of actions or materials, but not if a single event (tap, mouthed utterance, or sound) was repeated.

Humans↗
PubMed2004

3.0-T high-field magnetic resonance imaging of the female pelvis: preliminary experiences.

The purpose of this study was to evaluate if 3.0 T allows for clinically useful pelvic magnetic resonance imaging, i.e. if familiar image quality and tissue contrast can be achieved at 3.0 T as compared with at 1.5 T. Adapting a 1.5-T protocol to the 3.0-T environment is subject to a variety of factors. In order to reduce the number of potential variables, we chose two cornerstones: the 3.0-T sequence should have similar spatial resolution and acquisition time; furthermore, the contrast parameters repetition time (TR) and echo time (TE) were kept identical. Based on this modified 3.0-T T2-weighted turbo spin-echo sequence (TR/TE 2,705/80 ms; 0.7x1.04x4 mm measured voxel size; field of view 360 mm; 4.03-min scan time) we performed an intraindividual study on 19 patients with the 1.5-T sequence as the standard of reference. Two radiologists analyzed the examinations in consensus with regard to tissue contrast (visualization of zonal anatomy of the uterus and/or delineation of pathologic findings) rated on a three-point scale (3 is 3.0 T better; 2 is 3.0 T equal; 1 is 3.0 T worse than 1.5 T). In addition, the signal difference between muscle and bone marrow was measured as a marker for tissue contrast. The analysis of the image quality comprised the level of the artifacts (rated on a five-point scale: 1 is no artifacts; 5 is nondiagnostic study), the visual signal-to-noise ratio (rated on a three-point scale) and detail delineation. Only minor artifacts were observed at both 1.5 and 3.0 T; the difference was not statistically significant. The visual signal-to-noise ratio and the delineation of image details were rated equal for 1.5 and 3.0 T. With regard to image contrast, both qualitative analysis as well as quantitative analysis revealed comparable image contrast for the 1.5- and 3.0-T protocols. Pathological findings were seen equally well with both field strengths. Clinically diagnostic pelvic studies of high image quality can be obtained using a 3.0-T scanner with our modified examination protocol. To fully exploit the capability of the high-field technique, and to point out potential advantages, further intraindividual studies are needed, with the adjustment of other imaging parameters to the high-field environment.

Adult↗
PubMed2000

Activity in human frontal cortex associated with spatial working memory and saccadic behavior.

We examined, with event-related fMRI, two hypotheses about the organization of human working memory function in frontal cortex: (1) that a region immediately anterior to the frontal eye fields (FEF) (superior frontal cortex, SFC) is specialized for spatial working memory (Courtney, et al., 1998); and (2) that dorsolateral prefrontal cortex (PFC) plays a privileged role in the manipulation of spatial stimuli held in working memory (Owen, et al., 1996; Petrides 1994). Our delayed-response task featured 2-D arrays of irregularly arranged squares that were highlighted serially in a random sequence. The Forward Memory condition required maintenance of the spatio-temporal sequence, the Manipulate Memory condition required reordering this sequence into a new spatially defined order, the Guided Saccade condition required saccades to highlighted squares in the array, but no memory, and the Free Saccade condition required self-paced, horizontal saccades. The comparison of fMRI signal intensity associated with 2-D saccade generation (Guided Saccades) versus fMRI signal intensity associated with the delay period of the working memorials condition revealed no evidence for greater working memory-related activity than saccade-related activity in SFC in any individual subject, nor at the level of the group, and greater 2-D saccade than delay-period activity in three of five subjects. These results fail to support the hypothesis that spatial working memory-related activity is represented preferentially in a region of SFC anterior to the FEF (Courtney, et al., 1998). The comparison of maintenance versus manipulation of spatio-temporal information in working memory revealed significantly greater activity associated with the latter in dorsolateral PFC, but not in ventrolateral PFC or in SFC. These results suggest that the delay-related function of SFC is limited to the maintenance of spatial information, and that this region does not support the nonmnemonic executive control functions supported by dorsolateral PFC. These results also indicate that the preferential recruitment of dorsolateral PFC for the manipulation of information held in working memory applies to tasks employing spatial stimuli, as well as to tasks employing verbal stimuli (D'Esposito, et al., 1999); Petrides et al., 1993; Postle et al., 1999).

Acoustic Stimulation↗
PubMed1987

Molecular cloning of sequences from wingless, a segment polarity gene in Drosophila: the spatial distribution of a transcript in embryos.

In Drosophila the process of segmentation depends on the function of coordinate, gap, pair-rule and segment-polarity genes. Mutations in segment-polarity genes cause defects in the pattern of every segment. Here the cloning of sequences from a segment-polarity gene, wingless, and the in situ localization of a transcript in embryos are described. The transcript is first detected in the anterior and posterior regions of the blastoderm embryo at cellularization, and accumulates in a series of stripes in the extended germ band, one stripe per metameric unit. Each stripe is localized to the most posterior cells of each parasegment. The signal is predominantly epidermal, and transcript accumulates only transiently in the mesoderm and nervous system. This pattern of expression is discussed with respect to models of pattern formation in segmental units.

Journal Article↗
PubMed2026

Volumetric DNA microscopy for mapping spatial transcriptomes in three dimensions.

The architecture and function of biological systems are inherently three-dimensional, yet most existing spatial transcriptomic technologies remain restricted to thin tissue sections, limiting their capacity to resolve cellular organization and microenvironments within intact tissue volumes. To address this limitation, we developed volumetric DNA microscopy, a scalable, optics-free approach for spatial transcriptome profiling directly within intact biological specimens. The method encodes spatial information into DNA molecules that form a dense intermolecular network in situ, enabling the reconstruction of three-dimensional spatial relationships through short-read sequencing and computational analysis. Here we detail the complete workflow including in situ cDNA synthesis, spatial encoding through DNA nanoball formation, dual-scale proximity bridging between neighboring nanoballs and spatial reconstruction via geodesic spectral embedding. Sequencing libraries can be generated within 7-8 d by a competent graduate-level molecular biologist, followed by standardized downstream computational analysis. Because the workflow requires only routine molecular biology reagents and a benchtop sequencer, volumetric DNA microscopy provides a versatile platform for exploring genetic and morphological features in intact tissues.

Spatial Transcriptomics↗
PubMed1992

DNA sequences at and between the GC and TATA boxes: potential DNA looping and spatial juxtapositioning of the protein factors.

Regulation of gene expression in eukaryotes involves a complex assembly of DNA recognition sequence elements and their respective protein factors. The upstream promoter/enhancer sequences are position and orientation independent. Despite their variable distances from the TATA box and transcription start site, interaction between the protein activators and TATA general transcription factors takes place, enabling induced levels of transcription initiation. Here the intervening sequences between the GC and TATA boxes are examined as functions of their lengths. Regardless of the substantial differences in the spacer sizes, similar mono and dinucleotide distributions are noted. Purine-purine base pair steps, except for AA, are more frequent at and near the GC box in the 5' ends of the loops than in their 3' ends. Pyrimidine-pyrimidine base pair steps, except for TT behave similarly. AT and TA (as well as AA and TT) are more frequent in the 3' ends of the loops near the TATA. Examination of these distributions, as well as of the sequences composing the GC and TATA boxes indicates that the DNA in the upstream part of the loop is more rigid, whereas the downstream regions are far more flexible. The flexibility of the general TATA region may afford correct spatial juxtapositioning of the proteins with respect to each other, enabling interactions between the activators and the general transcription factors.

Base Composition↗
PubMed2004

Hippocampal function in cognition.

RATIONALE AND OBJECTIVES: Any consideration of cognitive disruption in schizophrenia quite naturally leads to questions concerning the cellular and molecular mechanisms underlying normal cognition. This review will describe emerging models for the cellular basis of cognitive processing in the hippocampus. METHODS AND RESULTS: This review will describe results from several laboratories that have used in vivo recording in behaving rodents to probe the role of the hippocampus in cognition. These exciting studies have indicated a broader role of the hippocampus in general information processing than was previously appreciated. These recent results suggest that the hippocampus is involved in minute-to-minute cognitive processing including spatial information processing, temporal sequencing, and formulating the relationships between objects in the environment. CONCLUSIONS: The hippocampus appears to play a major role in bringing together environmental signals and producing a cohesive and unified percept in the spatial and temporal domains. This new view of the role of the hippocampus in cognition fits strikingly well with models for schizophrenia hypothesizing hippocampal dysfunction as one cause of cognitive decline in schizophrenic patients.

Animals↗
PubMed1994

Evidence for separate motion-detecting mechanisms for first- and second-order motion in human vision.

Current theories of second-order motion perception postulate that such motion is detected by either a high-level mechanism which computes the temporal correspondences between "features" extracted from the image, or low-level motion mechanisms which operate on a nonlinear, neural transformation of the luminance profile of the image. Theories which favour the latter strategy either suggest that first- and second-order motion are detected by a common mechanism or else that distinct mechanisms exist for the two types of motion, both operating on similar principles. The aim of this study was to differentiate between these possibilities. Observers were required to judge the direction of multiframe motion sequences in which the frames alternated between sinusoidal variations in luminance (first order) and similar variations in contrast (second order). On each frame the modulation signal was displaced by some fraction of its spatial period. The motion sequences were designed such that integration of both types of frame (first and second order) would lead to unambiguous motion in a particular direction whilst separate analysis of first- or second-order frames alone would yield ambiguous motion. The results show clearly that observers were unable to integrate the first- and second-order frames of such motion sequences. However, when observers were presented with motion sequences in which the frames alternated between two, different types of second-order image (variations in the contrast or size of the elements constituting a random noise field) perceived direction was always consistent with integration of both image types. This is taken as support for models that suggest that first- and second-order motion are processed by distinct mechanisms in the visual system and that each mechanism is only sensitive to one type of motion. It is suggested that several varieties of second-order motion stimuli may be regarded as equivalent to contrast-modulated images when considered in terms of the effects of local spatiotemporal filtering operations carried out by the human visual system. In this respect, our results are consistent with the "texture grabber" concept of Werkhoven, Sperling and Chubb [(1993) Vision Research, 33, 463-485].

Contrast Sensitivity↗
PubMed2000

Prospective multiaxial motion correction for fMRI.

Corruption of the image time series due to interimage head motion limits the clinical utility of functional MRI. This paper presents a method for real-time prospective correction of rotation and translation in all six degrees of rigid body motion. By incorporating an orbital navigator (ONAV) echo for each of the sagittal, axial, and coronal planes into the fMRI pulse sequence, rotation and translation can be measured and the spatial orientation of the image acquisition sequence that follows can be corrected prospectively in as little as 160 msec. Testing of the method using a computerized motion phantom capable of performing complex multiaxial motion showed subdegree rotational and submillimeter translational accuracy over a range of +/-8 degrees and +/-8 mm of motion. In vivo images demonstrate correction of simultaneous through-plane and in-plane motion and improved detection of fMRI activation in the presence of head motion.

Artifacts↗
PubMed2004

Simultaneous cognitive operations in working memory after dual-task practice.

The authors tested the hypothesis that with adequate practice, people can execute 2 cognitive operations in working memory simultaneously. In Experiment 1, 6 students practiced updating 2 items in working memory through 2 sequences of operations (1 numerical, 1 spatial). In different blocks, imperative stimuli for the 2 sequences of operations were presented either simultaneously or sequentially. Initially, most participants experienced substantial dual-task costs. After 24 sessions of practice, operation latencies for simultaneous presentation were equal to the maximum of times for the 2 operations in the sequential condition, suggesting perfect timesharing. Experiment 2 showed that a reduction of dual-task costs requires practice on the combination of the 2 updating tasks, not just practice on each individual task. Hence, the reduction of dual-task costs cannot be explained by shortening or automatization of individual operations.

Cognition↗
PubMed2006

A flexible structure for fully scalable motion-compensated 3-D DWT with emphasis on the impact of spatial scalability.

We investigate the implications of the conventional "t+2-D" motion-compensated (MC) three-dimensional (3-D) discrete wavelet/subband transform structure for spatial scalability and propose a novel flexible structure for fully scalable video compression. In this structure, any number of levels of "pretemporal" spatial wavelet decomposition are performed on the original full resolution frames, followed by MC temporal decomposition of the subbands within each spatial resolution level. Further levels of "posttemporal" spatial decomposition may be performed on the spatiotemporal subbands to provide additional levels of spatial scalability and energy compaction. This structure allows us to trade energy compaction against the potential for artifacts at reduced spatial resolutions. More importantly, the structure permits extensive study of the interaction between spatial aliasing, scalability and energy compaction. We show that where the motion model fails, the "t+2-D" structure inevitably produces misaligned spatial aliasing artifacts in reduced resolution sequences. These artifacts can be removed by using pretemporal spatial decomposition. On the other hand, we also show that the "t+2-D" structure necessarily maximizes compression efficiency. We propose different schemes to minimize the loss of compression efficiency associated with pretemporal spatial decomposition.

Algorithms↗
PubMed2006

Cyanobacterial assimilatory nitrate reductase gene diversity in coastal and oligotrophic marine environments.

Cyanobacteria are important primary producers in many marine ecosystems and their abundances and growth rates depend on their ability to assimilate various nitrogen sources. To examine the diversity of nitrate-utilizing marine cyanobacteria, we developed PCR primers specific for cyanobacterial assimilatory nitrate reductase (narB) genes. We obtained amplification products from diverse strains of cultivated cyanobacteria and from several marine environments. Phylogenetic trees constructed with the narB gene are congruent with those based on ribosomal RNA genes and RNA polymerase genes. Analysis of sequence library data from coastal and oligotrophic marine environments shows distinct groups of Synechococcus sp. in each environment; some of which are represented by sequences from cultivated organisms and others that are unrelated to known sequences and likely represent novel phylogenetic groups. We observed spatial differences in the distribution of sequences between two sites in Monterey Bay and differences in the vertical distribution of sequence types at the Hawai'i Ocean Time-series Station ALOHA, suggesting that nitrogen assimilation in Synechococcus living in different ecological niches can be followed with the nitrate reductase gene.

Classification↗
PubMed2005

Brain arteriovenous malformations: measurement of nidal volume using a combination of static and dynamic magnetic resonance angiography techniques.

Arteriovenous malformations of the brain are complex vascular lesions that are an important cause of death and long-term disability. Currently, catheter angiography (CA) is the reference standard procedure for the diagnosis and follow-up of treated arteriovenous malformations (AVMs). This is an invasive procedure with potential risks. Magnetic resonance angiography (MRA) is commonly used in neurovascular imaging as a non-invasive alternative. Various MRA techniques have been used in the diagnosis and follow-up of AVMs but these have suffered from lack of temporal or spatial resolution. In this 60-patient study we describe the combination of two techniques: dynamic magnetic resonance digital subtraction angiography with a high temporal resolution, and a non-dynamic contrast-enhanced time-of-flight sequence with a high spatial resolution technique, in the assessment of AVM. The results showed an excellent correlation between MRA and CA measurement of both maximum linear dimension and AVM nidus volume.

Adult↗
PubMed2000

Human articular cartilage: influence of aging and early symptomatic degeneration on the spatial variation of T2--preliminary findings at 3 T.

PURPOSE: To determine if age and early symptomatic degeneration alter the spatial dependency of cartilage T2. MATERIALS AND METHODS: In 25 asymptomatic volunteers and six volunteers with symptoms of patellar chondromalacia, quantitative T2 maps of patellar cartilage were obtained with a multiecho, spin-echo magnetic resonance imaging sequence at 3.0 T. Spatial variation in T2 was evaluated as a function of participant age and symptoms. RESULTS: All asymptomatic volunteers demonstrated a continuous increase in T2 from the radial zone to the articular surface. In the population aged 46-60 years compared with younger volunteers, there was a statistically significant (P < .05) increase in T2 of the transitional zone. In symptomatic volunteers, the increase in T2 was larger in magnitude and focal in distribution. In five of the six symptomatic volunteers, the increase in T2 was greater than the 95% prediction interval determined from data in the corresponding age-matched asymptomatic population. CONCLUSION: Aging is associated with an asymptomatic increase in T2 of the transitional zone of articular cartilage. Preliminary results indicate this diffuse increase in T2 in senescent cartilage is different in appearance than the focally increased T2 observed in damaged articular cartilage.

Adult↗
PubMed2003

Multiple regulatory elements with spatially and temporally distinct activities control neurogenin1 expression in primary neurons of the zebrafish embryo.

The basic Helix-Loop-Helix gene neurogenin1 (ngn1) is expressed in a complex pattern in the neural plate of zebrafish embryos, demarcating the sites of primary neurogenesis. We have dissected the ngn1 locus to identify cis-regulatory regions that control this expression. We have isolated two upstream elements that drive expression in precursors of Rohon-Beard sensory neurons and hindbrain interneurons and in clusters of neuronal precursors in the anterior neural plate, respectively. A third regulatory region mediates later expression. Thus, regulatory sequences with temporally and spatially distinct activities control ngn1 expression in primary neurons of the zebrafish embryo. These regions are highly similar to 5' sequences in the mouse and human ngn1 gene, suggesting that amniote embryos, despite lacking primary neurons, utilize related mechanism to control ngn1 expression.

Amino Acid Sequence↗
PubMed2005

Infants' enumeration of actions: numerical discrimination and its signature limits.

Are abstract representations of number - representations that are independent of the particular type of entities that are enumerated - a product of human language or culture, or do they trace back to human infancy? To address this question, four experiments investigated whether human infants discriminate between sequences of actions (jumps of a puppet) on the basis of numerosity. At 6 months, infants successfully discriminated four- versus eight-jump sequences, when the continuous variables of sequence duration, jump duration, jump rate, jump interval and duration, and extent of motion were controlled, and rhythm was eliminated. In contrast, infants failed to discriminate two- versus four-jump sequences, suggesting that infants fail to form cardinal number representations of small numbers of actions. Infants also failed to discriminate between sequences of four versus six jumps at 6 months, and succeeded at 9 months, suggesting that infants' number representations are imprecise and increase in precision with age. All of these findings agree with those of studies using visual-spatial arrays and auditory sequences, providing evidence that a single, abstract system of number representation is present and functional in infancy.

Analysis of Variance↗