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PubMedDate not supplied

[Effect of weightlessness on the functions of perception and the reproduction of gravitational vertical in response to optokinetic stimulation].

In weightlessness spatial orientation largely depends on coordinated interaction of sensory systems involved in static orientation. The purpose of the present study was to quantify perception of spatial coordinates in response to optokinetic stimulation. Effects of weightlessness were simulated by dry water immersion hypokinesia. A custom-made optokinetic stimulator equipped with a device to measure perception of the gravitational vertical in response to optokinetic stimulation was used. A special platform with rubber bungee cords was employed to determine the role of the proprioceptive afferent input. It was demonstrated that during immersion day 1 the angle of erroneous perception of the vertical line consistently increased. By immersion day 3 the angle diminished suggesting adaptive developments. Additional proprioceptive inflow during immersion reduced significantly the error of perception. These findings indicate that the proprioceptive afferent input plays an important role in the mechanisms of spatial orientation at an early stage of exposure to weightlessness.

Adult↗
PubMed1996

Postural orientation modifications in autism in response to ambient lenses.

Autistic children often display abnormal postures, head tilts, and other spatial management dysfunctions. Methods were introduced to measure spatial orientation in tasks in a group of fourteen autistic children in Montreal, Canada. Ambient lenses were found to improve posture, correct head tilts, and improve ball catching abilities. A model of spatial orientation is described and recommendations are made to incorporate ambient lenses in treatment programs.

Adolescent↗
PubMed1996

Behavioural and neural bases of orientation in food-storing birds

Food-storing birds retrieve hoarded food by remembering the locations of large numbers of spatially dispersed caches. The basic patterns of spatial orientation in these animals have been established in research on two major groups of food-storing birds, chickadees and tits (Paridae), and jays and nutcrackers (Corvidae). Experiments using displacement of landmark arrays show that food-storing birds rely on visual information from nearby landmarks to locate concealed caches. The appearance of the cache sites themselves seems to be relatively unimportant in cache retrieval, perhaps because local features are subject to change during the lifetime of a cache. Under some conditions, food-storing birds use sun-compass information to orient their search for caches, but appear to integrate sun-compass information with landmark information. Lesions of the avian hippocampus disrupt cache retrieval and other spatial tasks in food-storing birds without disrupting the formation of simple associations. Comparative studies show that food-storing birds possess a hippocampus larger than that of non-food-storing birds, probably as an evolutionary consequence of their dependence on spatial orientation for cache retrieval. Experience with cache retrieval plays a role in the development of increased hippocampal size, and there are indications of seasonal variation in hippocampal size in food-storing species.

Journal Article↗
PubMed1978

Multivalued stimulus-response relation in isolated elasmobranch utricles.

The relation between a maintained spatial orientation and the corresponding fully adapted discharge rate was multivalued in all the afferents tonically sensitive to maintained spatial orientation observed in isolated utricles of Rhinobates productus. The spread of rate values was of the order of changes produced by natural tilts. The occurrence of multivaluedness in isolated receptors indicated that peripheral issues are sufficient. Two factors contributed: firstly, the side from which the orientation had been reached (i.e. "hysteresis"): higher adapted rates occurred when the preceding orientation was characterized by lower rates and when the corresponding transition caused acceleration; secondly, "spontaneous" rate variations, some of which resembled markedly, and interacted with, the effects of tilts. It was not possible to identify the basic mechanisms underlying these factors. The multivaluedness in the coding of maintained position, because of its constancy and magnitude, cannot be ignored. It, as well as the sensitivity to fast transients, must be taken into account in utricular models, in evaluations of information transmission, and in psychophysical explorations.

Action Potentials↗
PubMed1997

Covert visual spatial attention in boys with attention deficit hyperactivity disorder: lateral effects, methylphenidate response and results for parents.

We report three related studies of covert visual spatial orienting in child attention deficit hyperactivity disorder (ADHD). In Study 1, we examined covert visual spatial orienting in ADHD and comparison boys, Study 2 comprised a dose-response study of methylphenidate for the ADHD group, and Study 3 was an investigation of biological and adoptive parents. In contrast with comparison subjects (n = 17). ADHD boys aged 6-12 (n = 27) showed both slower reaction times overall and within-condition (lateral) asymmetries in reaction times. Specifically, boys with ADHD reacted more slowly to uncued targets in the left visual field than in the right visual field. Responses to stimuli in the two visual fields were differentially affected by methylphenidate for the ADHD group. Medication equalized visual field responses to the uncued targets, resulting in a significant cue x dose x visual field interaction. Further, medication altered the relative cue responsivity in the two visual fields, resulting in a significant dose x visual field interaction for the Validity Effect. Biological parents of ADHD boys (n = 16) also showed slower reaction times to uncued left visual field targets than to right visual field targets; in addition they showed slower response to invalidity cued targets in the right visual field. These literal effects were not observed in adoptive parents of ADHD boys (n = 12) or biological parents of comparison boys (n = 14). Possible abnormal hemispheric asymmetry of attention functions in boys with ADHD and their biological parents is discussed.

Adoption↗
PubMedDate not supplied

[Quantitative dependence of structure-antiseizure activity in a series of macrocyclic compounds].

In the present study we have further examined the influence of some structure parameters of macrocyclic polyethers upon their anticonvulsant activity in order to determine basic pharmacophore fragments. The anticonvulsant activity was studied experimentally for 25 new macrocyclic compounds, and their structure, physico-chemical properties, electron donor factors and atom charges were calculated using programs HyperChem-ChemPlus and HYBOT. The data about atomic properties were presented as a set functions of inter-atomic distances (Program MOLTRA). The cluster analysis revealed that studied compounds represent two independent groups which differ from chemical and pharmacological viewpoints. For first group, we have found that anticonvulsant activity of macrocycles is determined by their polarizability and spatial orientation of electron donor atoms. For another cluster the correlation was found between activity and spatial orientation of two hydrophobic fragments and electron donor atoms as well.

Animals↗
PubMed1989

Spatial and orientation specific integration in the tilt illusion.

Lateral inhibition across a population of cells in visual cortex which are tuned to local orientation has been proposed and widely accepted as a basic process in the analysis of contour in the visual field. The tilt illusion is usually explained in terms of this inhibition. Experiments are reported which cast new light on the analysis of visual orientation. It is shown that tilt illusions may be obtained with very thin inducing annuli which are spatially remote from the test figure. In experiments in which remote crossed-grating plaids were used, an illusion which was pattern (global) rather than component (local) selective was seen. It is difficult to account for these observations in terms of local inhibitory mechanisms. Rather, the results support the existence of a secondary mechanism which is involved in basic orientation analytic processes. The relevance of these observations to models of visual contour analysis is discussed.

Attention↗
PubMed2005

Reflexive orienting in spatial neglect is biased towards behaviourally salient stimuli.

Patients with spatial neglect are impaired when detecting contralesional targets presented shortly after an ipsilesional cue. This "disengagement" deficit is believed to reflect reflexive orienting towards ipsilesional stimuli that is independent of behavioural goals. Here, we show that the extent of this spatial bias depends on the behavioural salience of ipsilesional stimuli. Healthy participants, brain-injured patients without neglect and neglect patients reacted to ipsilesional and contralesional visual targets. Prior to target presentation, a visual cue similar or dissimilar to the target was presented at target position or opposite the target. Although participants did not react to the similar cue, it had high behavioural salience since it shared features with the target stimulus. Neglect patients showed dramatically increased reaction times to contralesional targets, but only when these followed behaviourally relevant ipsilesional cues. No decrease of performance was observed with irrelevant cues. This performance pattern was not due to perceptual similarity, since the same effect was found when cue and target were semantically related but differed perceptually. Importantly, semantically related cues ceased to attract attention when they were defined as behaviourally irrelevant. These results show that neglect patients only orient attention reflexively towards ipsilesional stimuli with high behavioural salience.

Adult↗
PubMed1985

Uncertainty relation for resolution in space, spatial frequency, and orientation optimized by two-dimensional visual cortical filters.

Two-dimensional spatial linear filters are constrained by general uncertainty relations that limit their attainable information resolution for orientation, spatial frequency, and two-dimensional (2D) spatial position. The theoretical lower limit for the joint entropy, or uncertainty, of these variables is achieved by an optimal 2D filter family whose spatial weighting functions are generated by exponentiated bivariate second-order polynomials with complex coefficients, the elliptic generalization of the one-dimensional elementary functions proposed in Gabor's famous theory of communication [J. Inst. Electr. Eng. 93, 429 (1946)]. The set includes filters with various orientation bandwidths, spatial-frequency bandwidths, and spatial dimensions, favoring the extraction of various kinds of information from an image. Each such filter occupies an irreducible quantal volume (corresponding to an independent datum) in a four-dimensional information hyperspace whose axes are interpretable as 2D visual space, orientation, and spatial frequency, and thus such a filter set could subserve an optimally efficient sampling of these variables. Evidence is presented that the 2D receptive-field profiles of simple cells in mammalian visual cortex are well described by members of this optimal 2D filter family, and thus such visual neurons could be said to optimize the general uncertainty relations for joint 2D-spatial-2D-spectral information resolution. The variety of their receptive-field dimensions and orientation and spatial-frequency bandwidths, and the correlations among these, reveal several underlying constraints, particularly in width/length aspect ratio and principal axis organization, suggesting a polar division of labor in occupying the quantal volumes of information hyperspace.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

The control of body orientation and center of mass location under asymmetrical loading.

This study examined how whole body center of mass (COM) in the medial-lateral direction and spatial orientation of body segments changed during quiet stance when a weight was loaded on asymmetrically on the right side of the pelvis. The load corresponded to 10 and 30% of body weight (BW) of each individual subject, and the stance width was varied from narrow (7.6 cm) to normal (20 cm) and to wide (33 cm). A total of 10 healthy young subjects (18-30 years of age) participated in the study. The results indicated that the COM location was significantly shifted towards the loaded side (about 1.2 cm with a 10% BW load and 3 cm with a 30% BW load). In addition, COM was closer to the center with a narrow stance (0.38 cm to the right of the center) than both normal and wide stance (about 1 cm to the right). However, the COM shifts for all test conditions were smaller (<50%) than that of the theoretically predicted values. The smaller shift in COM position appeared to be mostly due to the change in spatial orientation of the pelvis and lower extremity (about 2.5 degrees change with a 10% BW load, and 4.5 degrees change with a 30% BW load), while maintaining the upper body orientation relatively unchanged (less than 2 degrees with a 30% BW load). This strategy may allow increased stability of the upright stance with minimal amount of muscle activation.

Adolescent↗
PubMed2002

In situ analysis of the organic framework in the prismatic layer of mollusc shell.

A novel in situ analytic approach was constructed by means of ion sputtering, decalcification and deprotein techniques combining with scanning electron microscopy (SEM) and transmission electron microscope (TEM) ultrastructural analysis. The method was employed to determine the spatial distribution of the organic framework outside and the inner crystal and organic/inorganic interface spatial geometrical relationship in the prismatic layer of cristaris plicate (leach). The results show that there is a substructure of organic matrix in the intracrystalline region. The prismatic layer forms according to strict hierarchical configuration of regular pattern. Each unit of organic template of prismatic layer can uniquely determine the column crystal growth direction, spatial orientation and size. Cavity templates are responsible for supporting. limiting size and shape and determining the crystal growth spatial orientation, while the intracrystal organic matrix is responsible for providing nucleation point and inducing the nucleation process of calcite. The stereo hierarchical fabrication of prismatic layer was elucidated for the first time.

Animals↗
PubMed1986

Contribution of figural proportion, figural memory, figure-ground perception and severity of hearing loss to performance on spatial tests.

348 adolescents, 176 male and 172 female, were administered six different spatial tests. Awareness of figural proportion, figural memory, and figure-ground perception contributed significantly to performance on spatial visualization tests but not to performance on spatial orientation tests. Similarly, severity of hearing loss was correlated with scores on visualization tests but not on spatial-orientation tests.

Adolescent↗
PubMedDate not supplied

Orientation illusions in spaceflight.

Investigations of spontaneous illusory reactions were carried out during space-flights of various durations by ANKETA questionnaires (104 cosmonauts). From a total of 104 cosmonauts, 24, in addition, used a dictaphone to record a verbal description of the illusions and their sensations on tape. Analysis of data generated by ANKETA and the tapes thus recorded have shown that during adaptation to weightlessness, 98% of cosmonauts have noted the occurrence of various illusions of orientation (coordinate and kinetic): illusions pertaining to their position or illusions of self- and surround-motion. The development of spatial orientation illusions during and after flight is not limited to certain individuals, but is a general response of the sensory system to microgravity. These responses differ to some extent among individuals in severity, nature, time and duration of occurrence, and the dynamics of the process. Perceptual disorders may occur even if the cosmonaut feels well and experiences no anomalous autonomic reactions. The nature of spatial illusions was determined by the role and relative contribution of various types of sensory input to spatial orientation. After completion of the initial stage of adaptation to weightlessness, the perceptual disorders disappear. However, spontaneous illusory reactions were often observed after 50 days of exposure to weightlessness. The adaptation process during long-term spaceflight had an undulating course, in which adaptation and de-adaptation alternated. A classification of weightlessness illusions is proposed.

Adaptation, Physiological↗
PubMed1990

Relationship between two different measurements of field-dependence and athletic performance of adolescents.

Two different measures were used to test field dependence-independence, Group Hidden Figures Test and Portable Rod and Frame Test. The purpose of the study was to compare the advantages of these two measures in differentiating among adolescents who are active in individual and team sports and those who are not. 94 adolescent boys and girls were divided into three groups, as follows: 33 in individual sports, 31 in team sports, and 30 nonathletes. No correlation was found between the two measures. The Portable Rod and Frame Test was the better instrument for distinguishing among the groups. This test requires use of visual vs proprioceptive information to perceive the body's spatial orientation. The Group Hidden Figures Test requires more analytical intelligence. Since there are relationships among awareness of the body, spatial orientation, and physical activity of athletes, the Portable Rod and Frame Test seems to be more applicable to the task of distinguishing between and among athletes and nonathletes.

Adolescent↗
PubMed2004

Cerebral correlates of alerting, orienting and reorienting of visuospatial attention: an event-related fMRI study.

The identification of brain systems contributing to different aspects of visuospatial attention is of both clinical and theoretical interest. Cued target detection tasks provide a simple means to dissociate attentional subcomponents, such as alerting, orienting or reorienting of attention. Event-related functional magnetic resonance imaging (fMRI) was used to study neural correlates of these distinct attentional processes. Volunteers were scanned while performing a centrally cued target detection task. Four different types of trials (no cue, neutral cue, valid cue and invalid cue trials) with targets appearing either in the right or left hemifield were randomly intermixed. Behaviourally, the data provided evidence for alerting, spatial orienting and reorienting of attention. Neurally, the alerting effect was seen in bilaterally increased extrastriatal blood oxygenation level-dependent (BOLD) activity in neutral as compared to no cue trials. Neural correlates of spatial orienting were seen in anterior cingulate cortex, which was more active during valid as compared to neutral cue trials. Neural correlates of reorienting of attention, that is, higher BOLD activity to invalid as compared to validly cued trials were evident in several brain regions including left and right intraparietal sulcus, right temporo-parietal junction and middle frontal gyrus bilaterally. The data suggest that frontal and parietal regions are specifically involved in reorienting rather than orienting attention to a spatial position. Alerting effects were seen in extrastriate regions which suggest that increased phasic alertness results in a top-down modulation of neural activity in visual processing areas.

Adult↗