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Results for “Spatial orientation”

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At least 253 records · Page 14Linked to original sources

PubMed2005

Resolving visual interference during covert spatial orienting: online attentional control through static records of prior visual experience.

Models of attentional control usually describe online shifts in control settings that accommodate changing task demands. The current studies suggest that online control over distractor exclusion--a core component of visual selection--can be accomplished without online shifts in top-down settings. Measurements of target discrimination accuracy suggested that the degree of distractor exclusion was guided by retinotopic maps of the prior probability of distractor interference at the attended locations. These probability maps can be retrieved via object-based cues, and they interact with shifts of attention to elicit increased levels of distractor exclusion when it is most needed. Thus, static probability maps can provide an internal template that guides the resolution of visual interference as spatial attention traverses the visual field.

Attention↗

PubMed1979

Spatial orientation and distribution of antigens within human glomerular basement membrane.

Antibodies to GBM have a linear staining pattern along the GBM by immunofluorescence. In this study, we have examined the distribution of human GBM antigens using Goodpasture antibody and heterologous rabbit anti-human GBM antibody. Goodpasture sera and Goodpasture antibody eluted from diseased kidneys reacted as a single linear component within the GBM. Rabbit anti-human GBM was shown to react along distinctly separate zones of the inner and outer aspects of the GBM; the central portion of the GBM seemed to be nonreactive with this antibody. In comparison, Goodpasture antibodies reacted along the inner zone of the GBM but at a locus external to that reacting with heterologous rabbit anti-GBM antibody. These observations of linear binding of antibody to different sites along the GBM suggest a spatial organization of antigen not previously observed.

Anti-Glomerular Basement Membrane Disease↗

PubMed1992

Effect of post-training unilateral labyrinthectomy in a spatial orientation task by guinea pigs.

The effects of unilateral labyrinthectomy in guinea pigs have been studied on an angular orientation task consisting, in an open field, of running to a hidden goal oriented at 45 degrees with respect to the cephalocaudal axis of the animal placed in a starting-box. The task was conducted in light but in an homogeneous environment, i.e. without visual, auditory or olfactory cues indicating the location of the goal. A second group of animals was submitted to a similar task running to a hidden goal but the place of the goal was indicated by a colored card. All the animals were trained before the lesion and tested in their respective task for 1 month after the lesion. In the task conducted without conspicuous cues, animals were dramatically disturbed. In contrast, animals pretrained in the visually guided task were not impaired after the lesion. These results point out the important role of vestibular information in performing spatial tasks based on angular estimation, since, even if proprioceptive and visuokinesthetic information remain available, subjects seemed not able to maintain a correct angular trajectory. The trajectories being not disturbed in the visually guided task, one can exclude the hypothesis that such deficit was due to a purely motor disturbance.

Animals↗

PubMed1996

Alteration and recovery of the spatial orientation of the collagen network of articular cartilage in adolescent rabbits following intra-articular chymopapain injection.

We have used polarized light (POL) to monitor changes in the organization of the articular cartilage collagen network and matrix proteoglycans (PGs) after intra-articular injection of chymopapain (CP). POL viewing of sirius red stained sections revealed a loss of normal birefringence suggesting an apparent collapse of the collagen network following intra-articular CP. After 21 days, knees injected with 2.0 mg CP showed no return of normal birefringence, however, normal birefringence was noted in knees injected with only 0.2 mg CP. POL viewing of toluidine blue stained sections revealed a severe loss of matrix PGs followed by PG restoration in animals injected with 0.2 mg CP. The most important inference from the data is that articular cartilage can recover from enzyme-induced alterations in the spatial collapse of its fibrillar network. This is an important finding since it has often been inferred that damage to the collagen network leads invariably to progressive articular cartilage destruction.

Animals↗

PubMed1993

Letters as spatial-oriented shapes and/or graphemic signs: a developmental study of left- and right-handed girls during the period of learning to read.

This study is concerned with the problem of hemispheric specialization and/or cooperation in relation to development and manual laterality. The processing of alphabetic signs and its relationship to interhemispheric transfer and functional hemispheric asymmetries were studied by comparing left- and right-handed girls during acquisition of reading. The children perform matching tasks with letters having different orientations and with meaningless forms having the same orientations as the letters. Each subject performed the matching under three conditions: right/left intermanual transfer, left/right intermanual transfer, and dichaptic exploration. Results indicate: (1) A differentiated development between the two handednesses. (2) The functional lateralization change was different for left- and right-handed girls, a greater effect of the ability to identify the letter on matching tasks was observed for the right-handed children than for the left-handed children. These last results are discussed with regard to inter-hemispheric transfer and functional hemispheric asymmetry changes. We hypothesized a strategy difference between left- and right-handed girls and a difference in their ability to change their cognitive strategy (left-handers continue to favor a spatial coding with letters).

Brain↗

PubMed1989

Doppler color flow mapping studies of jet formation and spatial orientation in obstructive hypertrophic cardiomyopathy.

To help clarify the mechanism of outflow tract obstruction and systolic anterior motion of the anterior leaflet of the mitral valve and their relation to the geometry of the left ventricle, we studied left ventricular outflow tract flow in 20 patients with hypertrophic cardiomyopathy (HCM) using two-dimensional Doppler flow mapping. We compared our results with outflow tract flow in 10 patients with isolated valvular aortic stenosis, (AS) and with those in 10 healthy volunteers. In HCM, a 94- to 145-degree angle (mean 111.4 +/- 11.9 degrees) developed between the direction of left ventricular outflow tract flow acceleration and aortic valve outflow, resulting in posterolaterally directed left ventricular outflow jets. The angle of the outflow jet and the peak velocity of the jet measured with continuous wave Doppler (as an indicator of the severity of obstruction) correlated well (r = -0.81, SEE = 7.8 degrees). Jet narrowing during ejection measured just proximal to the point of systolic anterior motion was 42 +/- 11% in HCM and was weakly correlated with peak jet velocity (r = 0.61, SEE = 8.9 degrees). Aliasing of left ventricular outflow occurred proximal to systolic anterior motion of the mitral valve, and color M-mode demonstrated temporal and spatial flow acceleration proximal to systolic anterior motion, providing evidence for obstruction at that site. In AS, left ventricular outflow tract jets were more parallel to the axis of aortic outflow (129 to 153 degree, 138.4 +/- 8.1 degrees). Jet narrowing was only 8 +/- 5% compared to HCM (both p less than 0.05), and flow acceleration occurred proximal to the stenotic valve.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Decrease of contralateral neglect by neck muscle vibration and spatial orientation of trunk midline.

Three patients with a right hemisphere lesion and marked left-sided neglect without visual field defects were asked to detect and identify stimuli which were tachistoscopically presented in the left or right visual half-field. Neglect of stimuli presented in the contralesional left visual field, which was observed when the patient's body was in a normal upright position with trunk, head and gaze oriented straight ahead to the middle of the projection screen, could be reduced by vibrating the left posterior neck muscles as well as by turning the trunk 15 degrees to the left. In contrast, unspecific stimulation on the left side of the patient's body, produced by vibrating the left hand muscles or the proprioceptive signal induced by turning the head 15 degrees to the left, had no compensatory effects. The results showed that the afferent information about real lengthening of the left posterior neck muscles (produced by turning the trunk) as apparent lengthening of these muscles (produced by their vibration), leads to a remission of contralateral neglect. Thus, the proprioceptive input from the neck muscles, i.e. the head-on-trunk signal, appears to influence the extension of the neglected part of space in patients with neglect. The signal seems to contribute substantially to the neural generation of the egocentric frame of reference that allows the determination of body position with respect to visual space. We hypothesize that the reduction of neglect by vibration of the contralateral posterior neck muscles is based on a shift of the subjective spatial localization of the sagittal midplane in the contralesional direction and a corresponding alteration of the egocentric coordinate system necessary for visuomotor coordination and exploration of space.

Aged↗

PubMed2001

Use of cue configuration geometry for spatial orientation in human infants (Homo sapiens).

Research with both rats and human infants has found that after inertial disorientation, the geometry of an enclosed environment is used in preference over distinctive featural information during goal localization. Infants (Homo sapiens, 18-24 months) were presented with a toy search task involving inertial disorientation in 1 of 2 conditions. In the identical condition, 4 identical hiding boxes in a rectangular formation were set within a circular enclosure. In the distinctive condition, 4 distinctive hiding boxes were used. Infants searched the goal box and its rotational equivalent significantly more than would be expected by chance in the identical condition, showing that they were sensitive to the geometric configuration of the array of boxes. Unlike the results of studies using a rectangular enclosure, however, in the distinctive condition, infants searched at the correct location significantly more than at other locations.

Cues↗

PubMed2005

On the role of otoliths and semicircular canals in spatial orientation: Dynamics of the visually perceived eye level during gondola centrifugation.

The visually perceived eye level (VPEL) was measured during gondola centrifugation. Subjects (N = 11) were seated upright, facing motion in a swing-out gondola The head was adjusted so that Reid's baseline was tilted 10 degrees anterior end up. The subjects were requested to adjust the position of a small luminous dot so that it was perceived as gravitationally at eye level. In the 1-g environment, the VPEL was a few degrees below the true gravitational eye level (M = -1.75 degrees, SD = 1.90 degrees). After rapid acceleration of the centrifuge to 2 G (vectorial sum of the earth gravity force and the centrifugal force), there was an exponentially increasing depression of the VPEL. The initial value was -6.4 degrees +/- 5.2 degrees. During 10 min at 2 G, the VPEL approached an asymptotic value of -24.8 degrees +/- 5.4 degrees. The time constant showed a large interindividual variability, ranging from 59 to 1,000 sec (M = 261 sec, median = 147 sec). The findings are discussed, taking into consideration otolith-semicircular-canal interaction, as well as memory functions of the vestibular system.

Adult↗

PubMed1996

Representation of spatial orientation by the intrinsic dynamics of the head-direction cell ensemble: a theory.

The head-direction (HD) cells found in the limbic system in freely mov ing rats represent the instantaneous head direction of the animal in the horizontal plane regardless of the location of the animal. The internal direction represented by these cells uses both self-motion information for inertially based updating and familiar visual landmarks for calibration. Here, a model of the dynamics of the HD cell ensemble is presented. The stability of a localized static activity profile in the network and a dynamic shift mechanism are explained naturally by synaptic weight distribution components with even and odd symmetry, respectively. Under symmetric weights or symmetric reciprocal connections, a stable activity profile close to the known directional tuning curves will emerge. By adding a slight asymmetry to the weights, the activity profile will shift continuously without disturbances to its shape, and the shift speed can be controlled accurately by the strength of the odd-weight component. The generic formulation of the shift mechanism is determined uniquely within the current theoretical framework. The attractor dynamics of the system ensures modality-independence of the internal representation and facilitates the correction for cumulative error by the putative local-view detectors. The model offers a specific one-dimensional example of a computational mechanism in which a truly world-centered representation can be derived from observer-centered sensory inputs by integrating self-motion information.

Animals↗

PubMed1978

Spatial orientation of microtubules in contractile fibroblasts in vivo.

Contracting fibrous tissues from skin wounds in pigs, and scars around silicone implants in humans, contained fibroblasts that had multiple bundles of 60--80 A microfilaments with electron-dense bodies, features typical of contractile fibroblasts both in vivo (myofibroblasts) and in vitro. These in vivo fibroblasts contained many 220 A diameter microtubules, which paralleled plasma membrane in these myofibroblasts strongly suggests a bracing or scaffolding function.

Animals↗

PubMed1984

A Golgi analysis of the primate globus pallidus. II. Quantitative morphology and spatial orientation of dendritic arborizations.

The morphology of pallidal neurons was analyzed quantitatively in Golgi-impregnated brains of men and macaques (Macaca irus). Selected neurons were drawn with a camera lucida and reconstructed from serial sections. Dendritic arborizations were analyzed in three dimensions using a video computer microscope (Yelnik et al., '81). Morphological (topological and metrical) parameters were computed, and the overall geometry of arborizations was studied in three dimensions with the aid of principal component analysis (Yelnik et al., '83). Statistical tests were used in order to compare human with simian large neurons and the lateral with the medial pallidum. All neurons were found to belong to a single neuronal population. Particular neurites may be added randomly onto pallidal dendrites, mainly in the lateral pallidum. Large pallidal neurons are characterized by sparsely branched dendritic arborizations (4 stems, 13 tips) with thick, smooth, and long dendrites (longest dendrite = 1,000 micron, total dendritic length = 7,600 micron). All arborizations are discoidal in shape with mean dimensions of 1,500 X 1,000 X 250 micron. Pallidal discs are always parallel to the lateral border of each pallidal nucleus and thus perpendicular to striatal axons to which they present their greatest extent. They may be traversed by a large number of these axons. The existence of other pallidal neuronal groups, "intermediate" and "local circuit" neurons, identified in their fine morphological features by François et al. ('84), was confirmed quantitatively in the present study.

Animals↗

PubMed1994

Preflight adaptation training for spatial orientation and space motion sickness.

Two part-task preflight adaptation trainers (PATs) are being developed at the NASA Johnson Space Center to preadapt astronauts to novel sensory stimulus conditions similar to those present in microgravity to facilitate adaptation to microgravity and readaptation to Earth. This activity is a major component of a general effort to develop countermeasures aimed at minimizing sensory and sensorimotor disturbances and Space Motion Sickness (SMS) associated with adaptation to microgravity and readaptation to Earth. Design principles for the development of the two trainers are discussed, along with a detailed description of both devices. In addition, a summary of four ground-based investigations using one of the trainers to determine the extent to which various novel sensory stimulus conditions produce changes in compensatory eye movement responses, postural equilibrium, motion sickness symptoms, and electrogastric responses are presented. Finally, a brief description of the general concept of dual-adapted states that underly the development of the PATs, and ongoing and future operational and basic research activities is presented.

Adaptation, Physiological↗

PubMed1997

Perception of spatial orientation in spasmodic torticollis. Part I: The postural vertical.

Estimates of points of entering and exiting from upright posture were obtained from 25 seated, restrained patients with idiopathic spasmodic torticollis (ST) and matched normal subjects exposed to cycles of 1.5 degrees/s tilts in a flight simulator. Estimates were obtained for displacements in roll and pitch about upright and for yaw tilts about a rostrocaudal, "barbecue," axis with the subjects supinated. For both pitch and roll, normal subjects estimated entering upright when they were still approximately 1 degree from machine upright and perceived themselves to be upright through a mean arc of 6 degrees. In barbecue tilt, entering upright was estimated at 0.2 degree for an arc of 6 degrees. Patients estimated entering upright at 2.8 degrees in roll and 3 degrees in pitch but estimated exiting upright at the same tilt as normal subjects; that is, they were less specific in detecting verticality. Patients were normal in barbecue tilt. No relationship between tilt estimates and head deviation was found. There were no differences between normal subjects when tested with their head in normal posture and with an assumed tilt of 20 degrees. Normal subjects probably based their estimates on combined vestibular-somatosensory signals, whereas torticollis patients appeared to derive more from a vestibular signal. However, patients referred the vestibular signals to the trunk long axis when asked to indicate the whole-body vertical. The findings suggest disruption of the normal combined vestibuloproprioceptive mechanism for detecting body uprightness in ST.

Adult↗

PubMed1997

Perception of spatial orientation in spasmodic torticollis. Part 2: The visual vertical.

Twenty-nine patients with idiopathic spasmodic torticollis (ST) and matched normal control subjects were asked to align a target line to perceived earth vertical [visual vertical (VV)]. Settings were made against a whole-field random-dot background that was either stationary or rotating around the line of sight, and subjects performed the task upright and lying horizontally on their sides. Normal subjects were tested both head upright and after assuming a voluntary head tilt. Patients with ST set the VV close to true upright with a minimal deviation toward tilt of the head in contrast to normal subjects assuming a head tilt who set the VV in the opposite direction to the head tilt (Müller "E" effect). Settings against the spinning disk were biased in the direction of rotation similarly for both subject groups. Settings made against static or spinning disk performed when subjects lay horizontally were tilted in the direction of recumbence (Aubert "A" effect) similarly for both subject groups. When attempting to set the target line parallel to the long axis of the face, patients with head tilt set the line to upright, whereas normal subjects correctly estimated their tilts. One hypothesis offered to explain these results is that the patients referenced only their upright trunk for vertical and did not make use of neck proprioceptive or vestibular signals of head tilt so that all settings were made as if the trunk and head were upright. Alternatively, patients may have used only otolith signals as the reference for upright, and these are recalibrated in ST patients with head tilt. The pathological deviation becomes accepted as upright posture, and VVs and facial orientation are estimated as if the head were upright. In either case the findings indicate abnormal processing of the perception of visual verticality in ST patients.

Adult↗

PubMed1997

Spatial orientation of tissue-type plasminogen activator bound at the melanoma cell surface.

Human melanoma cells produce tissue-type plasminogen activator (tPA) which is bound to the cell surface where it effectively mediates generation of plasmin. The present study is focused on analysis of involvement of the tPA domains in binding of the enzyme to the cell surface. The extent of plasminogen activation by tPA of melanoma cells was measured using an immunocapture assay. The activator anchored to solid surface via monoclonal antibodies directed to the individual domains of the activator exhibited variable enzymatic activity. The tPA was the most effective when bound by the antibodies against kringle-1 or kringle-2. Accessibility of the epitopes within cell surface-bound tPA was probed by the same set of monoclonal antibodies. FACS analysis showed that the epitopes within the finger/growth factor domain one part of the kringle-2 domain and the active site epitope were the most exposed. The kringle-1 domain epitope and the protease region epitope appeared partially exposed. Full-length melanoma-derived tPA and three recombinant domain-deletion variants of tPA were compared for their capacity to bind to the melanoma cells. The estimated IC50 value for the melanoma-derived tPA was 2.3 +/- 0.25 microM. Comparable IC50 values were found for the tPA variant lacking the finger domain (3.6 +/- 0.6 microM) as well as for the variants consisting only of the kringle-2 and protease domains (7.5 +/- 0.45 microM). In contrast the value found for a tPA variant lacking the kringle-2 domain was > 100 microM. The consistent results obtained by the three different experimental approaches provide evidence that tPA binds to melanoma cells via its kringle-2 domain but binding sites within kringle-1 domain and protease domain may support the interaction. The finger domain did not contribute to the binding.

Antibodies, Monoclonal↗

PubMed1994

Processes underlying young children's spatial orientation during movement.

Children between 1.5 and 4 years old were tested for their ability to relocate a hidden object after a 180 degrees self-produced movement around an array of four locations. In one task the object's location relative to the other locations could be uniquely defined within one dimension, while in another two dimensions were needed to do this. No differences emerged between conditions, and by 3 years few errors occurred, despite the fact that children were unable to view the array during movement. This indicates either that young children encounter no specific difficulty in coordinating dimensions or that they solved the task without recourse to such a system. An error analysis supports the second possibility. Children apparently tackled the task by a system directly related to body movement, since errors were frequently the result of incomplete compensation for movement around the array. In a second study in which the four containers were placed in contact, children's performance declined and the relation between direction of movement and error was replaced by some evidence for updating on the near-far dimension accompanied by failure to update the left-right dimension. Thus children appear to change strategy when the problem requires more precise specification of target location.

Child, Preschool↗

PubMed1994

Spatial orientation of extraocular muscle EMG responses to tilt in the rabbit during postnatal development.

Unanaesthetized pigmented rabbits 2-45 days of age were gradually tilted (15 degrees steps) over 360 degrees around three orthogonal body axes. The multiunit electromyogram activity of superior rectus (SR) and superior oblique (SO) extraocular muscles was recorded with chronically implanted pairs of fine wire electrodes after each tilt step. The integrated EMG activity of the extraocular muscles in response to static tilt stimulation was trigonometrically related to tilt angle in all age groups. Each eye muscle was characterized by a typical locus of tilt positions which resulted in maximum integrated EMG activity. This locus was described by a vector of tonic vestibular activation (TVA) within the head coordinate system. The orientation of these TVA vectors within the coordinate system of the rabbit's head and, therefore, the coordination of tonic eye muscle activation in response to the position of the animal in the gravitational field did not change with postnatal age in the rabbit. Therefore, eye muscles are already capable of responding to static vestibular stimulation for the stabilization of gaze when visual information becomes available to the rabbit pups. The EMG responses to static tilt stimulation were principally determined by the scalar product of the gravity vector and the muscle's TVA vector. The response of the extraocular muscles to this effective gravitational stimulus was unchanged during the postnatal development of the rabbit: excitatory stimuli resulted in an approximately linear increase of the integrated EMG activity, inhibitory stimuli resulted in a smaller decrease to a minimum value. The correlation between the effective strength of excitatory gravity stimuli and the EMG activity of the extraocular muscles increased significantly at the time of postnatal eye opening. Since the strongest responses of SR and SO to static tilt were observed in intermediate roll-pitch positions that correspond closely to the planes of the vertical semicircular canals, a common reference frame for the cooperation of maculo-ocular and ampullo-ocular reactions is suggested.

Acceleration↗