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PubMed1997

Physiological and biomechanical aspects of orienteering.

Orienteering is an endurance running event which differs from other running sports both in its cognitive element and in the type of terrain encountered. The demands of overcoming this terrain are not manifest in significant differences between orienteers and road runners in somatotype, though elite female orienteers have consistently been shown to have higher levels of adiposity (> 19%) than elite road runners. High aerobic power in orienteers (up to 63 and 76 ml/kg/min in women and men, respectively) is coupled with lower anaerobic performance. While leg strength is generally not high when compared with other athletic specialties, female orienteers have relatively good leg flexion strength. The energy cost of running is greatly increased in rough terrain. Oxygen cost was 26% higher while running in a forest when compared with road running. Biomechanical differences in stride pattern contribute towards this increased demand. Despite the high energy demands during competition, orienteers pace themselves such that their mean heart rate remains within the range of 167 to 172 beats/min, despite large fluctuations. The rough terrain encountered in orienteering results not only in a high energy cost but also in a higher incidence of sport-specific injuries, particularly to the ankle. Minor injuries such as cuts and bruises are common during competition.

Anthropometry↗
PubMed2000

Temporal characteristics of line orientation identification.

The hypothesis that identification of line orientation is based on different mechanisms--a detector mechanism at large orientation differences and a computational one at small orientation differences--was tested in three experiments. The first two experiments compared reaction time and time of complete temporal summation (tc) in two tasks, line detection and line orientation identification. Identification at orientation differences 15 degrees or more was similar to detection in several respects, suggesting that it was accomplished according to the principle of "labeled lines." In agreement with the initial hypothesis, identification at differences smaller than 15 degrees had a slower time course and could not be explained by the "labeled lines" principle. Experiment 3 explored the orientation acuity as a function of exposure duration and stimulus energy. Energy could not completely substitute for time in providing high orientation acuity, a result suggesting the involvement of neurophysiological mechanisms of large time constants.

Adult↗
PubMed2000

Orientation tuning of shape from shading.

Four experiments were performed to assess the effect of different orientations and direction of lighting on the visual processing of shaded or bipartite disks. In the first two experiments, observers were presented with nine different shading orientations from 0 degree to 180 degrees. Targets were detected in a rapid and parallel fashion for shaded disks when the orientation of the shading gradient was not horizontal (90 degrees) or oriented at 67.5 degrees. Search asymmetries favoring the detection of "pock" targets over "ball" targets were found for all orientations. The search rates for bipartite disks were similar to the shaded disks at 0 degree, 22.5 degrees, and 90 degrees but not for intermediate orientations, and no search asymmetries were found. These differences suggest that shaded displays and bipartite displays are processed by different underlying mechanisms. The third experiment showed that the direction of the light source (left or right) had no influence on search asymmetries around the 90 degrees point. Shading gradient orientation affected magnitude estimates of depth in the fourth experiment. These experiments show that the visual system's "assumption" of overhead lighting is broadly tuned.

Adult↗
PubMed1994

Upright versus upside-down faces: how interface attractiveness varies with orientation.

A choice experiment is reported in which all pairs and triples of faces from a set of eight moderately attractive faces were presented, both upright and upside down, to 103 subjects. In each orientation, the subjects had to select the face that appeared more (pairs) or most (triples) attractive to them. For each orientation, the preference probabilities that arose from the pair and triple comparisons could be described by the BTL rule (Luce, 1959). Thus, each face was represented by two scores, one reflecting its attractiveness in the upright orientation and the other reflecting its attractiveness in the inverted orientation. Orientation affected the preference probabilities. Qualitatively, score ratios between faces decreased from upright to inverted orientation, suggesting that the faces became less discriminable by inversion. Quantitatively, the effect of inversion could be described by a simple rule that assumes a face's two attractiveness scores to be affinely related across orientations. This result indicates that inversion affected all faces about equally. The present findings are discussed with respect to faces' first- and second-order relational properties, a distinction emphasized in current theories of face perception. They suggest that the processing of first- and second-order relational properties is impaired by inversion to roughly the same degree.

Adult↗
PubMedDate not supplied

[Orientation and simultaneous visuospatial synthesis in dementia and depression].

The presented paper discusses the orientation processes and simultaneous visuospatial synthesis ability in patients with dementia and depression. The disturbances of the orientation processes and the simultaneous visuospatial synthesis ability have proved characteristic of patients with dementia. The disorder of simultaneous visuospatial synthesis ability constituted one of the cognitive limits in patients with dementia. Patients with dementia aided themselves with long-term memory and the retrieval processes ability in the orientation processes. In patients with dementia simultaneous visuospatial synthesis ability, orientation processes, attention, short-term memory, retrieval processes decreased together with progression of the dementia processes. The simultaneous visuospatial synthesis ability in patients with depression was maintained at a high level. Memory and visuospatial learning and simultaneous visuospatial synthesis ability reflected aptly the level of the orientation processes in patients with depression. Only patients with depression helped themselves with the simultaneous visuospatial synthesis ability in the orientation processes. In ageing simultaneous visuospatial synthesis ability decreased together with age. Notional abstract thinking was related to the orientation processes and the simultaneous visuospatial synthesis ability only in those ageing.

Aged↗
PubMed2001

Normalization models applied to orientation masking in the human infant.

Human infants can discriminate the orientation of lines within the first week after birth (Atkinson et al., 1988; Slater et al., 1988) but have immature orientation-selective pattern masking until after 6 months of age (Morrone and Burr, 1986). Here the development of orientation processing is further examined using a visual-evoked potential paradigm and normalization models of pattern masking. Contrast response functions were measured for 1 cycle per degree (cpd) gratings, counterphase-reversed in contrast at either 3.3 or 5.5 Hz. A second 1 cpd, 20% contrast, 8.3 Hz grating of either the same or orthogonal orientation was added as a mask. Evoked responses associated with the test grating, the mask, and intermodulation between the two were individually extracted using spectral analysis of the scalp-recorded EEG. Adults exhibited orientation selectivity in the masking of their test component responses and in nonlinear intermodulation between the test and mask stimuli. Infants <5 months old, however, demonstrated nonselective masking or a reversed selectivity in their responses to the test component, with adult-like orientation selectivity in their intermodulation responses. Within the context of a normalization model of pattern masking, the results are consistent with the existence of oriented filters early in life the responses of which are normalized immaturely until approximately 5 months of age.

Adult↗
PubMed2003

[Space and spatial orientation].

Space and spatial orientation has been a subject of interest of researchers for many years. Spatial orientation can be divided into cued navigation and place navigation. The latter requires more complex neuronal computations and is considered to be a model of higher cognitive functions in animals. Allothetic orientation is based on determining the location of the subject with respect to orientating cues and gradients in its surrounding. Idiothetic orientation involves integrating the information generated during active and passive self-motion in order to obtain the actual position of the subject with respect to the starting point. This article reviews the historical evolution of spatial concepts, the types of orientation, and their neuronal implementation. Description of the most widely used methods of studying mechanisms of spatial orientation is also included.

Animals↗
PubMed1989

Effects of field orientation during 700-MHz radiofrequency irradiation of rats.

Ketamine-anesthetized Sprague-Dawley rats were exposed to far-field 700-MHz continuous-wave radiofrequency radiation (RFR) in both E and H orientations. Irradiation was conducted at whole-body average specific absorption rates (SARs) of 9.2 and 13.0 W/kg (E and H, respectively) that resulted in approximately equivalent colonic specific heating rates (SHRs). Exposures were performed to repeatedly increase colonic temperature by 1 degree C (38.5 to 39.5 degrees C). Tympanic, tail, left and right subcutaneous (toward and away from RFR source), and colonic temperatures, arterial blood pressure, and respiratory rate were continuously recorded. In spite of equivalent colonic SHRs and the reduced E-orientation average SAR, the right subcutaneous, tympanic, and tail SARs, SHRs and absolute temperature increases were significantly greater in E than in H orientation. The cooling rate at all monitoring sites was also significantly greater in E than in H orientation. Heart rate and mean arterial blood pressure significantly increased during irradiation; however, changes between orientations were not different. Respiratory rate significantly increased during irradiation in H, but not in E orientation. These results indicate that during resonant frequency irradiation, differences occur in the pattern of heat deposition between E- and H-orientation exposure. When compared with previous investigations performed at supraresonant frequencies, the lower level of cardiovascular change in this study was probably related to the lower periphery-to-core thermal gradient.

Animals↗
PubMed1985

[Standardness and invariability of the detector tuning of neurons in the orientation column of the visual cortex of the cat].

The variability of neuron orientation tuning in separate columns and the degree of it stability under changes in levels of the contrast between stimulus and background were studied in experiments on unanesthetized, relaxed cats. Several types of orientation columns were revealed: with a relatively high, standard and stable orientation tuning; with a widely changing orientation tuning from neuron to neuron; with invariance to contrast level; with variant orientation tuning; with mixed (invariant-variant) properties. In the columns, standard-nonstandard properties, on the one hand, and properties of invariability-variability, on the other hand, could combine in different ways. More often differences of orientation tuning within a column were observed between neurons of upper and lower cortical layers. Possible distinctions in the functional role of types of orientation tuning in columns described and in mechanisms of formation of detector properties of their neurons are discussed.

Animals↗
PubMed1983

[Double orientation tuning of visual cortex neurons in the cat].

Orientation tuning of 148 visual cortex neurons was investigated in immobilized unanaesthetized cats. The light slit of the optimal size flashing in the receptive field was used as a stimulus. It was found that 88 neurons (59%) had double orientation tuning: preferred and additional. Additional orientation was either orthogonal or at a sharp angle to the preferred orientation. In 64% neurons double orientation was found only after a change of the contrast between stimulus and background. This kind of tuning in many neurons appeared only at definite moments after the beginning of the stimulus. Model analysis showed that double orientation tuning might be a consequence of the specific structure of neuronal receptive fields. The functional meaning of double orientation tuning and its role in the detection of visual images signs are discussed.

Animals↗
PubMed1978

The relationship between retinal receptor orientation and photoreceptor optics.

At this time, based on still-restricted studies, it would seem that a fundamental property of vertebrate receptor optics is anterior pointing by receptors. The anterior pointing locus is most probably a point approximating the center of the exit pupil of the eye. There is evidence for the recovery of orientation when that orientation is disturbed. One or more mechanisms mediate that orientation, and we must seek to define and understand their functional properties. We must better define how disturbance in orientation influences vision. Briefly stated, substantially disturbed receptors have reduced light-guiding capability (and hence reduced sensitivity), reduced contrast sensitivity (caused by increased cross talk and so forth), and reduced resolution capability. These combine to creat a detectable (but not necessarily common) form of amblyopia [30]. In a sense, these cases of poor acuity would seem to represent a failure of the photoreceptor alignment system. An interesting set of theories has evolved in relation to receptor alignment in the neonate. There is considerable mechanical hydraulic stress on the newborn ocular vascular system at the time of delivery. Retinal hemorrhages and transient edema of the optic papilla following intracranial pressure rise and rapid decompression later during delivery of the head commonly occur. These can readily causd disturbances in receptor alignment. In some instances the macula is involved. While hemorrhages are apparently rapidly absorbed, if foveal receptors remain misaligned during the critical period (not yet really defined) for the development of vision, central fine-resolution capability may fail to develop. That is, subsequent elaboration of the visual system is dependent upon the quality of the optically transmitted and neurally transformed retinal image during the critical period for visual development. If the capability for realignment exists and occurs after part or all of the critical period, then signs of a prior receptor disarray may no longer be present in later years, but reduced resolution capability can persist. There is interesting literature on the subject [63-68]. K. Simons is currently reviewing this literature as part of his dissertation. Simons points out that the rupture of vessels may in fact partially serve as a safety valve protective of the infant in the presence of these substantive forces, i.e., fine-vessel rupture may limit the potential for damage to the eye. At this stage of investigation it is dangerous to carry speclation too far. Thus not only must we consider the mechanism for orientation, the nature of a possible error signal, and the mechaniisms for maintaning orientation and relating the retina to its substrate, but we must also analyze the consequences of disturbances in these mechanisms in relation to the individual's visual capability. Of equal importance is the need to understand the mechanisms and processes leading to failure of recovery of proper photoreceptor orientation...

Animals↗
PubMed1996

Covert orienting of attention in the rat and the role of striatal dopamine.

Attention can be directed to a location in the absence of overt signs of orienting, a phenomenon termed "covert orienting." The ability to orient attention covertly has been well documented in humans, but recent progress has been made with the operational definition of the processes involved in covert orienting. Reaction times to visual targets are quickened when attention is drawn to the location of the subsequent target, and processes such as disengagement, maintenance, and movement of attention can be dissociated by using this method. The possible involvement of striatal dopamine in covert orienting is disputed, with conflicting reports of deficits in covert orienting in patients with Parkinson's disease. To examine the significance of dopamine in the striatum in attentional processes, a test of covert orienting, analogous to that used in humans, was devised for the rat. Unilateral dopamine-depleting lesions of the striatum resulted in increases in mean reaction times contralateral to the side of the lesion, but reaction times did not change differentially as a function of the requirements to maintain, disengage, or shift attention. These findings add additional support to the hypothesis that the deficit that appears as hemineglect observed after striatal damage reflects a motor impairment rather than damage in neural systems underlying mechanisms for directing attention.

Animals↗
PubMed1998

Achievement orientation and fear of success in Asian American college students.

One hundred eighty-five Asian American undergraduates participated in a study designed to examine the relationships among gender, acculturation, achievement orientation, and fear of academic success. Acculturation was modestly correlated with achievement orientation. Endorsement of Asian and Anglo values were significantly related to individual-oriented achievement. Marginal significance, however, was obtained for endorsement of Asian values and beliefs to social-oriented achievement. These findings suggest that persons with a bicultural identity tend to adopt a multifaceted achievement style. Achievement orientation, in turn, predicted fear of academic success, with gender and perceived discrepancies from parental achievement values contributing minimal additional variance. Social-oriented achievement was related to high fear of academic success, whereas an individualistic orientation buffered against such conflicts.

Acculturation↗
PubMed2000

Visualization of nerve fiber orientation in gross histological sections of the human brain.

Diffusion weighted magnetic resonance imaging (DWMRI) allows visualization of the orientation of the nervous fibers in the living brain. For comparison, a method was developed to examine the orientation of fibers in histological sections of the human brain. Serial sections through the entire human brain were analyzed regarding fiber orientation using polarized light. Direction of fibers in the cutting plane was obtained by measuring the azimuth with the lowest intensity value at each point, and inclination of fibers in the section was evaluated using fuzzy logic approximations. Direction and inclination of fibers revealing their three-dimensional orientation were visualized by colored arrows mapped into the images. Using this procedure, various fiber tracts were identified (pyramidal tract, radiatio optica, radiatio acustica, arcuate fascicle, and 11 more). Intermingled fibers could be separated from each other. The orientation of the fiber tracts derived from polarized light microscopy was validated by confocal laser scanning microscopy in a defined volume of the internal capsule, where the fiber orientation was studied in four human brains. The polarization method visualizes the high degree of intermingled fiber bundles in the brain, so that distinct fiber pathways cannot be understood as solid, compact tracts: Neighbouring bundles of fibers can belong to different systems of fibers distinguishable by their orientation.

Aged↗
PubMed2003

Preferred collagen fiber orientation in the human mid-shaft femur.

Collagen fiber orientation is one aspect of the microstructure of bone that influences its mechanical properties. While the spatial distribution of preferentially oriented collagen is hypothesized to reflect the effects of loading during the process of aging, its variability in a modern human sample is essentially unknown. In a large sample (n = 67) of autopsied adults, the variability of collagen fiber orientation in the mid-shaft femur was examined in relation to age and sex. Montaged images of entire 100 microm thick cross-sections were obtained using circularly polarized light microscopy (CPLM) under standardized illuminating conditions. An automated image-analyzing routine divided images into 48 segments according to anatomical position. Average gray values (varying with orientation) were quantified for each segment, and one-way ANOVA with Tukey HSD post hoc tests were applied to assess differences between segments. Collagen fiber orientation appeared to be nonrandomly distributed across the mid-shaft femur sample; however, no single "human" pattern was identified. Individual variation, unexplainable by age, sex, or body size, exceeded population-level trends. Differences between age and sex groups suggest there is a strong correspondence between collagen fiber orientation and tissue-type distributions. The minimal consistencies demonstrated here may reflect mechanical forces induced at the femoral mid-shaft. However, the myriad of other factors that may influence collagen fiber orientation patterning, including growth trajectories, metabolic and nutritional status, and disease states, must be explored further. Only then, in conjunction with studies of other structural and material properties of bone, will we be able to elucidate the linkages between microstructure and functional adaptation in the human mid-shaft femur.

Adult↗
PubMed2003

Circularly polarized light standards for investigations of collagen fiber orientation in bone.

Bone exhibits positive form birefringence dominated by and dependent upon the orientation of its collagen. The biomechanical efficacy of bone as a tissue is largely determined by collagen fibers of preferred orientation and distribution (and corresponding orientation of mineral crystallites), and evidence is accumulating to demonstrate that this efficacy extends to function at the organ level. This study has three aims. The first is to provide a Background to the study of circularly polarized light (CPL) investigations of collagen fiber orientation in bone. The significance of preferred collagen fiber orientation in bone, linearly polarized light and CPL imaging principles, and a short history of CPL studies of mammalian functional histology are reviewed. The second is to describe, in some detail, methodological considerations relating to specimen preparation and imaging appropriate for the quantitative analysis of preferentially oriented collagen. These include section transparency, section thickness, the uniformity of the illuminating system, and CPL paraphernalia. Finally, we describe a grey-level standard useful for quantitative CPL, based upon mineralized turkey tendon, which shall be provided to investigators upon request. When due consideration is paid to specimen preparation and imaging conditions, quantitative assessment of collagen fiber orientation provides insight into the effects of mechanical loading on the skeleton.

Animals↗
PubMed2003

Templateless assembly of molecularly aligned conductive polymer nanowires: a new approach for oriented nanostructures.

Although oriented carbon nanotubes, oriented nanowires of metals, semiconductors and oxides have attracted wide attention, there have been few reports on oriented polymer nanostructures such as nanowires. In this paper we report the assembly of large arrays of oriented nanowires containing molecularly aligned conducting polymers (polyaniline) without using a porous membrane template to support the polymer. The uniform oriented nanowires were prepared through controlled nucleation and growth during a stepwise electrochemical deposition process in which a large number of nuclei were first deposited on the substrate using a large current density. After the initial nucleation, the current density was reduced stepwise in order to grow the oriented nanowires from the nucleation sites created in the first step. The usefulness of these new polymer structures is demonstrated with a chemical sensor device for H(2)O(2), the detection of which is widely investigated for biosensors. Finally, we demonstrated that controlled nucleation and growth is a general approach and has potential for growing oriented nanostructures of other materials.

Journal Article↗
PubMed1991

Planar differences in nuclear area and orientation in the subventricular and intermediate zones of the rat embryonic neocortex.

Nuclear area and orientation in the subventricular and intermediate zones was studied quantitatively in coronal vs. sagittal sections of the dorsomedial neocortex. Nissl-stained methacrylate-embedded normal rat embryos were studied between embryonic days (E) 13 and E22. The area of nuclear profiles and the degrees their long axes (defined as a straight line through the two most distant points in the nuclear profile) deviated from the horizontal (defined as parallel to the pial membrane) were determined with a computer-graphics program. Because the nucleus is the most clearly outlined structure in embryonic cells, the area and orientation of the nucleus was taken to reflect the overall size and orientation of the cell body. Nuclear area is larger in the coronal plane than it is in the sagittal plane, especially between E17 and E20. Cell body orientation in the subventricular and lower intermediate zones is predominantly horizontal in the coronal plane and predominantly vertical in the sagittal plane. In the upper intermediate zone, cell body orientation is predominantly vertical in both planes, but more so in the sagittal plane. These data indicate that the majority of cell bodies in the subventricular and lower intermediate zones have a horizontally oriented, flattened elliptical shape with their larger diameters lying within the coronal plane and their smaller diameters in the sagittal plane. Because of the flattening, the cell bodies falsely appear to be vertically oriented in the sagittal plane. Qualitative observations in horizontal sections confirmed the quantitative computer analysis. These results are related to other findings with [3H]thymidine autoradiography concerning cell migration and the sojourn of cells in the subventricular and intermediate zones.

Animals↗