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At least 541 records · Page 30Linked to original sources
PubMed1995

Effect of orientation in haptic reproduction of line length.

We investigated the accuracy of haptic reproduction of line length and whether accuracy is influenced by line orientation. 13 blindfolded subjects felt along different line lengths at various orientations in the horizontal plane, then reproduced the line lengths in the same orientation as that felt. Efforts were made to equate learning and reproductive scanning movements. Reproductions of line lengths were a nonveridical power function of their true lengths, but the power function exponents did not differ across spatial orientations. It was concluded that people can encode line lengths across spatial orientations by a common power function if care is taken to equate proprioceptive information across learning and reproduction.

Adult↗
PubMed1986

M.I.T./Canadian vestibular experiments on the Spacelab-1 mission: 2. Visual vestibular tilt interaction in weightlessness.

Adaptation to weightlessness includes the substitution of other sensory signals for the no longer appropriate graviceptor information concerning static spatial orientation. Visual-vestibular interaction producing roll circularvection was studied in weightlessness to assess the influence of otolith cues on spatial orientation. Preliminary results from four subjects tested on Spacelab-1 indicate that visual orientation effects were stronger in weightlessness than pre-flight. The rod and frame test of visual field dependence showed a weak post-flight increase in visual influence. Localized tactile cues applied to the feet in space reduced subjective vection strength.

Adaptation, Physiological↗
PubMed1979

Biological investigations aboard biosatellite Cosmos-782.

The Cosmos-782 flight from 25 November to 15 December 1975, carried biological experiments designed to study the effects of weightlessness on insects and fish and on gravitropism and growth in several seed varieties. Investigations carried out on Drosophila melanogaster measured the frequency of recessive lethal mutations and the change in genetic distances in the sex chromosome. The study of Fundulus heteroclitus eggs and fry compared the effects of weightlessness and artificial gravity. Plants experiments studied spatial orientation of over and underground organs of Pinus silvestris and Crepis capillaris seeds. Other investigations used Phycomyces blakesleanus to compare spatial orientation and growth and development in weightlessness and artificial gravity.

Animals↗
PubMed2002

Transient topographical disorientation.

Transient topographical disorientation (TTD) is a short-lasting inability to find one's way in a familiar environment, while the patient remains conscious and is able to recall what happened. We report the study of 10 patients with episodes of TTD, studied on the days following the last episode. The episodes of TTD could be separated into two types: the patients either reported difficulties in spatial orientation with preserved abilities to recognize landmarks and objects, or the difficulties appeared with the recognition of landmarks. Tests exploring spatial orientation, as well as higher visuoperceptive capacities were altered in most of the patients and brain SPECT showed hypoperfusion of the right hemisphere in all patients, which could also be demonstrated 2 years later in some cases. Altogether, our findings suggest that TTD is frequently associated with a more persistent right hemisphere dysfunction of unknown cause. This chronic alteration could represent either a sequel of the acute episode or a preexisting right hemisphere deficit, which inclined the acute insult to be manifested as TTD.

Adult↗
PubMedDate not supplied

[Anthropogenic EMF effects on the condition and function of natural ecosystems].

A review of Russian and foreign studies of EMF effects on living environment was made. Vast range of EMF frequencies and intensities affect on functions and condition of ecosystems. Even non-thermal EMF levels could cause reversible changes in physiological process regulation. Some changes were observed in animal behavior such as motive activity, spatial orientation, reduction of ability to form a conditioned response. Some animal species (some insects, birds, reptiles) use electromagnetic fields for spatial orientation during migration. Biological communities are very sensitive to EMF effects and could become the biological indicators of electromagnetic pollution.

Animals↗
PubMed1979

Tangential orientation and spatial order in dendrites of cat auditory cortex: a computer microscope study of Golgi-impregnated material.

In the tangential plane (parallel to the pial surface) dendrites in the primary auditory cortex (A1) of cat were found to exhibit preferentially oriented growth. This was shown by means of a computer microscope study of Golgi-Cox stained neurons as seen in 100 micrometers and 300 micrometers thick tangential sections. Two techniques were used to represent the 3-dimensional structure of dendrites: the "dendritic stick" and the "dendritic trumpet". The former dismembers a dendrite into its individual segments; the latter considers a dendrite as an entity and represents it by its centroid, its moments and the spatial dispersionof its branches. Both statistical and Fourier analyses of the data show that within the tangential plane there is a significant and consistent orientation of the dendritic sticks in a dorso-ventral direction which seems correlated with the cortical isofrequency contours observed in electrophysiological maps of the A1 region. The dendritic trumpet analyses also show a distinctly non-random vertical distribution of pyramidal cell basal dendrites but not of stellate cell dendrites.

Animals↗
PubMed1997

Relationships between the orientation and moment arms of the human jaw muscles and normal craniofacial morphology.

It has been suggested that subjects with increased vertical craniofacial dimensions have relatively oblique orientated jaw muscles with a reduced possibility to restrain the vertical component of craniofacial growth. To test this hypothesis, relationships were investigated between the spatial orientation of the jaw muscles and the craniofacial morphology. Computer reconstructions of the external shape of the jaw muscles of 30 adult males with a normal skull were made with the use of serial magnetic resonance imaging (MRI) scans. The orientation of the jaw muscles was defined by a regression line through the centroids of the serial cross-sections. Sagittal and frontal projections of the moment arms of the muscles were measured with respect to the centre of the ipsilateral condyle. Craniofacial morphology was analysed three-dimensionally using lateral head films and coronal MRI scans. The cephalometric data were analysed statistically using regression and factor analyses. Six cephalometric factors with Eigen values higher than 1 were correlated with jaw muscle orientation and moment arm data, using a multiple regression analysis. The anterior face height factor was significantly correlated with the orientation of the jaw opening muscles in the sagittal plane but was not significantly correlated with the orientation of the mandibular elevators. The sagittal moment arms of the mandibular elevators showed significant correlations with the factors describing the gonial angle and the posterior face height. It was concluded that the variation of spatial orientation of the human jaw closing muscles is predominantly associated with the variation of mandibular morphology (expressed by the gonial angle) and the posterior face height. The orientation of the jaw opening muscles shows significant relationships with anterior vertical craniofacial dimensions. The hypothesis that persons with an increased anterior face height have relatively oblique orientated jaw elevators was rejected.

Adult↗
PubMed1997

A topographic study of ERPs elicited by visual feature discrimination.

The functional properties and topographic distribution of event-related potential (ERP) components elicited by visual discrimination of orientation, spatial frequency, spatial location, and color were investigated. ERPs were recorded from 28 electrode sites from 16 adult subjects. Five ERP components were measured: N1 (peak latency = 160 ms), P2 (250 ms), anterior N2 (260 ms), posterior N2 (280 ms), and P3 (400 ms). N1 and P2 were more negative when a stimulus was a target, showing the selection negativity effect. Feature-specific effects on component amplitude or topography varied by component. N1 and P2 were sensitive to stimulus orientation and location. Anterior or posterior N2 was sensitive to orientation, spatial frequency, and location. P3 varied with orientation, but not with other stimulus features. Cross-task comparisons of ERPs to vertical line segments in the color, orientation, and location discrimination tasks indicated that P2 and N2, but not N1 and P3, were sensitive to changes in task-demand. These data provide topographic evidence that ERP components in the 160-400 ms time domain can be differentiated on the basis to processing of specific visual features, and reflect neurophysiologically distinct visual pathways in the human cortex.

Adult↗
PubMed2000

The role of the inertia tensor in kinesthesis.

We report experiments directed at the ability of humans to perceive the spatial orientation of occluded objects, to position an occluded limb relative to targets or directions in the environment, and to match the spatial orientation of occluded contralateral limbs. Results suggest that each of these abilities is tied to the inertial eigenvectors of each object or limb, which correspond to the object's or limb's principal axes of rotational inertia. It is suggested that the mechanisms supporting the perception of intact limbs, neuropathic or anesthetized limbs, prosthetic devices, and hand-held tools and implements via kinesthesis may be one and the same--the detection of movement-produced physical invariants such as the inertia tensor. While the research reported presently has focused on the perception of intact limbs and hand-held objects, future research should be directed at possible generalizations of this work to a variety of clinical populations, including those involving peripheral neuropathies and prosthetic devices.

Arm↗
PubMed1992

Eigenvectors of the inertia tensor and perceiving the orientation of a hand-held object by dynamic touch.

Subjects wielded an object, hidden from view, and reported the orientation in which the object was positioned in the hand. The object consisted of a stem with two branches forming a V attached perpendicularly to the stem's distal end. The branches were differentially weighted so that the same spatial orientation of the object was associated with different orientations of its principal (symmetry) axes or eigenvectors. Perceived orientation was found to be dependent on the eigenvectors of the object's inertia tensor, computed about the point of rotation in the wrist, rather than on its spatial orientation. The results underscore the significance of the inertia tensor to understanding the perception of spatial properties by dynamic touch.

Adult↗
PubMed2001

Influence of different natural physical fields on biological processes.

In space flight conditions gravity, magnetic, and electrical fields as well as ionizing radiation change both in size, and in direction. This causes disruptions in the conduct of some physical processes, chemical reactions, and metabolism in living organisms. In these conditions organisms of different phylogenetic level change their metabolic reactions undergo changes such as disturbances in ionic exchange both in lower and in higher plants, changes in cell morphology for example, gyrosity in Proteus (Proteus vulgaris), spatial disorientation in coleoptiles of Wheat (Triticum aestivum) and Pea (Pisum sativum) seedlings, mutational changes in Crepis (Crepis capillaris) and Arabidopsis (Arabidopsis thaliana) seedling. It has been found that even in the absence of gravity, gravireceptors determining spatial orientation in higher plants under terrestrial conditions are formed in the course of ontogenesis. Under weightlessness this system does not function and spatial orientation is determined by the light flux gradient or by the action of some other factors. Peculiarities of the formation of the gravireceptor apparatus in higher plants, amphibians, fish, and birds under space flight conditions have been observed. It has been found that the system in which responses were accompanied by phase transition have proven to be gravity-sensitive under microgravity conditions. Such reactions include also the process of photosynthesis which is the main energy production process in plants. In view of the established effects of microgravity and different natural physical fields on biological processes, it has been shown that these processes change due to the absence of initially rigid determination. The established biological effect of physical fields influence on biological processes in organisms is the starting point for elucidating the role of gravity and evolutionary development of various organisms on Earth.

Adaptation, Physiological↗
PubMed2004

Plantar foot pressure responses to changes during dynamic trans-tibial prosthetic alignment in a clinical setting.

Alignment of a lower limb prosthesis refers to the spatial orientation of the prosthetic components and socket with respect to one another. During the process of dynamic alignment, a prosthetist repeatedly modifies this spatial orientation and observes the amputee's resulting walking pattern, eventually arriving at an alignment that is judged to be optimal. Quantification of the effect of each alignment modification and correlation of the magnitude of modification with the changes in gait could improve understanding of the process and promote an evidential base for practice. This investigation quantified bilateral plantar foot pressures in six trans-tibial amputee subjects during the process of dynamic alignment at prosthetists' clinics during regularly scheduled appointments. Outcomes of changes in prosthetic alignment during the clinical dynamic alignment process were determined to be quantifiable via plantar pedobarography. Changes in the angle between the pylon and the socket in the frontal plane produced predictable shifts in foot pressure between medial and lateral foot regions under the prosthesis, and typically shifted pressure to the lateral region of the contralateral foot, regardless of the direction of the modification. Temporal parameters revealed that subjects initially adopt a conservative locomotor pattern after an alignment change but within a few steps begin to refine their gait and approach more symmetrical single limb support times. Plantar pedobarography provides the clinician with potentially useful information to augment dynamic alignment and provides a tangible record of the results of the process.

Adult↗
PubMed1991

[The motion sickness under reversing goggles (1st report)].

We observed locomotion and motion sickness in 10 normal adults wearing reversing goggles while moving outdoors. Horizontal reversal of the visual field produced moderate to severe ataxia and motion sickness in all subjects except one. There was marked variability in the sensitivity among different subjects. In contrast, vertical reversal produced no symptoms. Confusion of information relation to spatial orientation possibly caused both the motion sickness and abnormal locomotion. Horizontal reversal of visual information produces disorientation because visual information is equal in importance to that from the semicircular canals. In the case of vertical reversal of visual information, orientation may be assured by gravity. The present study suggests that motion sickness is a biological signal alerting the organism to loss of spatial orientation rather than a mere autonomic symptom produced by mismatched sensory information. It appears that motion sickness is accompanied by dysequilibrium and abnormality of locomotion.

Adult↗
PubMed1980

Spatial correlates of hippocampal unit activity are altered by lesions of the fornix and endorhinal cortex.

Behavioral and electrophysiological evidence supports the role of the hippocampus in the processing of spatial information. In the present study, neuronal activity recorded from chronically implanted hippocampal microelectrodes was correlated with a rat's spatial orientation while traversing a radial maze for food reward. Place units were found in all fields of the dorsal hippocampus and dentate gyrus. Rotation of the maze relative to extramaze cues failed to disrupt the intact animal's spatial task performance of the spatial correlates of the unit activity. Lesions of the fornix or entorhinal cortex disrupted performance of the task. Unit activity correlated to the animal's spatial orientation was also disrupted by either lesion. There was no correlation between the disruption of the unit activity and location of the unit within hippocampal fields. Unit activity from lesioned animals showed correlation to the physical properties of the maze rather than to the orientation of the maze in space. These results further support the role of the hippocampus in the processing of spatial information.

Animals↗
PubMed1987

Radiological prerequisites for spatial intracoronary orientation and quantitation in interventional cardiology.

The prerequisite for the safe performance of an intracoronary intervention is an optimal angiographic visualization. This includes high resolution film and video equipment and the acquisition of spatial information about anatomic details during the procedure. The geometric properties of modern biplane multidirectional X-ray equipment allow for exact spatial computations. These can be used for optimal portraying of coronary segments by computed triple orthogonal projections. In addition, an improvement in quantitative angiography is possible by calculation of the exact radiological magnification factor of coronary stenosis.

Angiography↗
PubMed2000

Involuntary listening aids seeing: evidence from human electrophysiology.

It is well known that sensory events of one modality can influence judgments of sensory events in other modalities. For example, people respond more quickly to a target appearing at the location of a previous cue than to a target appearing at another location, even when the two stimuli are from different modalities. Such cross-modal interactions suggest that involuntary spatial attention mechanisms are not entirely modality-specific. In the present study, event-related brain potentials (ERPs) were recorded to elucidate the neural basis and timing of involuntary, cross-modal spatial attention effects. We found that orienting spatial attention to an irrelevant sound modulates the ERP to a subsequent visual target over modality-specific, extrastriate visual cortex, but only after the initial stages of sensory processing are completed. These findings are consistent with the proposal that involuntary spatial attention orienting to auditory and visual stimuli involves shared, or at least linked, brain mechanisms.

Acoustic Stimulation↗
PubMed2006

Spatial ability subfactors and their influences on a computer-based information search task.

OBJECTIVE: The present study examined the relationship between two distinct subfactors of spatial ability and performance in an information search task modeled on browsing the Web. BACKGROUND: Previous studies have found relationships between various measures of spatial ability and performance in a wide variety of computer-based tasks. METHOD: In the search task 101 participants (18-29 years of age) searched for the answer to a question by navigating the system. They completed the experimental task as well as a battery of cognitive ability measures that included two different measures of spatial ability. RESULTS: The results indicate that spatial orientation ability was related to performance with tasks that were high in their navigational requirement (engendered by the use of a novel aid), whereas spatial visualization was unrelated to performance in any task condition. CONCLUSION: A closer inspection of the cognitive requirements of a task may reveal what interventions could be most useful when designing computer systems or developing training programs. APPLICATION: Given the unique differences between the different spatial abilities, the current results suggest the design of navigational aids that place less demand on spatial orientation ability.

Adolescent↗