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PubMed1997

The role of vision and spatial orientation in the maintenance of posture.

This article reviews and analyzes the role of vision and spatial orientation in maintaining posture and balance. The key issues that relate to the development of postural control across the life span are discussed. Use of vision as a critical source of information that specifies spatial orientation in the environment is considered. We argue that the visual system functions as part of the perception-action cycle as promoted in ecological psychology by James Gibson. We compare and contrast theory and evidence of both standard and ecological accounts of how the visual system perceives the information and the findings relative to the role of the retinal vision in processing and acting on information related to motion. Changes in the ambient optical array (optical flow) as a non-force field are compared with gravity-based perturbations relative to the possible influence of the non-force field to changes in the motor system. Finally, a summary of some of our own work is presented, with comments about implications for further research and possible applications to clinical practice.

Humans↗
PubMed1999

Effects of head-slaved and peripheral displays on lane-keeping performance and spatial orientation.

To improve the efficiency of images presented in low-cost vehicle simulators, the virtual viewing direction (i.e., the direction in which the image is rendered) can be head-slaved, the display can be surrounded with a less detailed peripheral image, or both. Three simulator experiments were used to evaluate the effect of these techniques on lane-keeping performance and spatial orientation. In Experiment 1, vehicle references or a head-slaved display (HSD) provided feedback on the virtual viewing direction. Vehicle references improved lane-keeping performance somewhat with a standard 50 degrees h x 50 degrees v display. An HSD (50 degrees h x 50 degrees v) allowed better steering performance, but not to the levels obtained with a wide display (150 degrees h x 50 degrees v). Experiments 2a and 2b evaluated the effects of surrounding the HSD with a less detailed peripheral image and of moving the HSD discretely or continuously. With the peripheral image, lane-keeping performance (Experiment 2a) and spatial orientation (Experiment 2b) were similar to those with a wide display. In both experiments, performance with the discretely moving HSD was superior to that with the continuously moving HSD. The results show that low-cost driving simulators can be equipped with more efficient displays that are as effective as wide displays for lane-keeping and spatial orientation.

Adult↗
PubMed1994

Effects of spaceflight on ocular counterrolling and the spatial orientation of the vestibular system.

We recorded the horizontal (yaw), vertical (pitch), and torsional (roll) eye movements of two rhesus monkeys with scleral search coils before and after the COSMOS Biosatellite 2229 Flight. The aim was to determine effects of adaptation to microgravity on the vestibulo-ocular reflex (VOR). The animals flew for 11 days. The first postflight tests were 22 h and 55 h after landing, and testing extended for 11 days after reentry. There were four significant effects of spaceflight on functions related to spatial orientation: (1) Compensatory ocular counterrolling (OCR) was reduced by about 70% for static and dynamic head tilts with regard to gravity. The reduction in OCR persisted in the two animals throughout postflight testing. (2) The gain of the torsional component of the angular VOR (roll VOR) was decreased by 15% and 50% in the two animals over the same period. (3) An up-down asymmetry of nystagmus, present in the two monkeys before flight was reduced after exposure to microgravity. (4) The spatial orientation of velocity storage was shifted in the one monkey that could be tested soon after flight. Before flight, the yaw axis eigenvector of optokinetic afternystagmus was close to gravity when the animal was upright or tilted. After flight, the yaw orientation vector was shifted toward the body yaw axis. By 7 days after recovery, it had reverted to a gravitational orientation. We postulate that spaceflight causes changes in the vestibular system which reflect adaptation of spatial orientation from a gravitational to a body frame of reference. These changes are likely to play a role in the postural, locomotor, and gaze instability demonstrated on reentry after spaceflight.

Animals↗
PubMed1998

Control of spatial orientation of the angular vestibuloocular reflex by the nodulus and uvula.

Spatial orientation of the angular vestibuloocular reflex (aVOR) was studied in rhesus monkeys after complete and partial ablation of the nodulus and ventral uvula. Horizontal, vertical, and torsional components of slow phases of nystagmus were analyzed to determine the axes of eye rotation, the time constants (Tcs) of velocity storage, and its orientation vectors. The gravito-inertial acceleration vector (GIA) was tilted relative to the head during optokinetic afternystagmus (OKAN), centrifugation, and reorientation of the head during postrotatory nystagmus. When the GIA was tilted relative to the head in normal animals, horizontal Tcs decreased, vertical and/or roll time constants (Tc(vert/roll)) lengthened according to the orientation of the GIA, and vertical and/or roll eye velocity components appeared (cross-coupling). This shifted the axis of eye rotation toward alignment with the tilted GIA. Horizontal and vertical/roll Tcs varied inversely, with T(chor) being longest and T(cvert/roll) shortest when monkeys were upright, and the reverse when stimuli were around the vertical or roll axes. Vertical or roll Tcs were longest when the axes of eye rotation were aligned with the spatial vertical, respectively. After complete nodulo-uvulectomy, T(chor) became longer, and periodic alternating nystagmus (PAN) developed in darkness. T(chor) could not be shortened in any of paradigms tested. In addition, yaw-to-vertical/roll cross-coupling was lost, and the axes of eye rotation remained fixed during nystagmus, regardless of the tilt of the GIA with respect to the head. After central portions of the nodulus and uvula were ablated, leaving lateral portions of the nodulus intact, yaw-to-vertical/roll cross-coupling and control of Tc(vert/roll) was lost or greatly reduced. However, control of Tchor was maintained, and T(chor) continued to vary as a function of the tilted GIA. Despite this, the eye velocity vector remained aligned with the head during yaw axis stimulation after partial nodulo-uvulectomy, regardless of GIA orientation to the head. The data were related to a three-dimensional model of the aVOR, which simulated the experimental results. The model provides a basis for understanding how the nodulus and uvula control processing within the vestibular nuclei responsible for spatial orientation of the aVOR. We conclude that the three-dimensional dynamics of the velocity storage system are determined in the nodulus and ventral uvula. We propose that the horizontal and vertical/roll Tcs are separately controlled in the nodulus and uvula with the dynamic characteristics of vertical/roll components modulated in central portions and the horizontal components laterally, presumably in a semicircular canal-based coordinate frame.

Animals↗
PubMed1999

Multimodal spatial orientation deficits in left-sided visual neglect.

Patients with right-sided temporo-parietal lesions often show contralesional neglect. However, neglect patients may also show spatial-perceptual deficits beyond the bisection and space exploration deficits frequently assessed in the horizontal plane, that is, deficits in the judgment of the subjective visual vertical or horizontal. In a recent study (Kerkhoff, G. & Zoelch, C.. Disorders of visuo-spatial orientation in the frontal plane in patients with visual neglect following right or left parietal lesions. Exp. Brain Res., 1998;122:108-120) we found significant perturbations in the perception of these three visual spatial axes in patients with contralesional neglect from right or left parietal lesions. To examine if this finding extends also to another modality we investigated how neglect patients perform tasks of visual- and tactile-spatial judgments of axis-orientation in the frontal plane. Visual-spatial and tactile-spatial judgments of the subjective vertical, horizontal and a right oblique orientation were obtained from patients with and without neglect as well as from normal subjects. Patients with left neglect showed a significant, contraversive tilt of all three visual-spatial axes (+5.6 degrees to +9.5 degrees, counterclockwise), and of the three tactile-spatial axes as well (+5.2 degrees to +10.5 degrees, counterclockwise). In contrast, right and left hemisphere lesioned control patients without neglect and normal control subjects showed unimpaired visual and tactile-spatial judgments (constant errors: < 1.0 degree). Difference thresholds in the visual-spatial tasks and unsigned errors in the tactile-spatial tasks were selectively elevated in the neglect group in contrast to all other subject groups. Spatial orientation deficits were significantly associated with the severity of clinical neglect (r = 0.55-0.88), and with the patients' ambulation performance (r = 0.45-0.70). Furthermore, crossmodal axis orientation tests in two neglect patients showed a similar counterclockwise tilt of +5 degrees to +15 degrees, suggesting a similar spatial deficit in both modalities. Orientation judgments were significantly aggravated by a 25 degree-tilt of the head to the left, as tested in one neglect patient, while a comparable rightward head-tilt improved spatial judgments in both modalities. This suggests that spatial orientation judgments are significantly modulated by gravitational input in neglect patients. Together these results are interpreted as evidence for multisensory spatial orientation deficits in neglect patients which are modulated by head-position and are related to their accompanying postural impairment.

Adult↗
PubMed2000

Effects of centrolateral or medial thalamic lesions on motor coordination and spatial orientation in rats.

The effects of central lateral (CL) or medial thalamic lesions were evaluated on tests requiring balance and equilibrium (rotorod, stationary beam, and hole-board), and spatial orientation (Morris water maze). Lesions of the medial nuclei impaired rotorod and spatial orientation, while CL lesions impaired only rotorod performance. Neither lesion affected stationary beam and hole-board tests or visuomotor guidance while swimming toward a visible platform. These spatial and sensorimotor deficits cannot be explained by reduced cerebral activation, but instead are attributable to specific projections from the anterior intralaminar nuclei to the basal ganglia and neocortex.

Animals↗
PubMed2004

Functional neuroanatomy of spatial orientation processing in Turner syndrome.

Turner syndrome (TS), a neurogenetic disorder characterized by the absence of one X chromosome in a phenotypic female, is frequently associated with visuospatial impairments. We investigated the neural mechanisms underlying deficits in spatial orientation processing in TS. Thirteen subjects with TS and 13 age-matched typically developing controls underwent neuropsychological assessments and were scanned using functional MRI while they performed easy and difficult versions of a judgment of line orientation (JLO) task. Controls and subjects with TS activated parietal-occipital regions involved in spatial orientation during the JLO task. However, activation was significantly less in the TS group. Control subjects responded to increased task difficulty by recruiting executive frontal areas whereas subjects with TS did not activate alternate brain regions to meet increased task demands. Subjects with TS demonstrate activation deficits in parietal-occipital and frontal areas during the JLO task. Activation, and possibly deactivation, deficits in these areas may be responsible for the visuospatial deficits observed in females with TS.

Adolescent↗
PubMed2000

Spatial orientation of atherosclerotic plaque in non-branching coronary artery segments.

It has been postulated that atherosclerotic plaque deposition is spatially related to regions of low shear in non-branching vessel segments. Intravascular ultrasound (IVUS) allows precise spatial orientation of coronary artery plaque formation in humans. The objective of this study was to test the hypothesis that coronary plaques have a higher prevalence on the myocardial side in regions that encounter low surface shear stress. IVUS allows the determination of the inner versus the outer curve of the vessel based on vascular and perivascular landmarks. We studied 30 consecutive patients pre-intervention using IVUS and measured vessel area, lumen area and plaque area (vessel-lumen area) during a motorized pullback at 1 mm intervals. Vessel segments near a side branch (within two times the diameter of the vessel) were excluded from analysis because of flow disturbances. All plaques were classified as concentric or eccentric and all eccentric plaques were further divided with respect to their spatial orientation in the vessel into quadrants: myocardial (inner curve, lower shear stress), epicardial (outer curve, higher shear stress) and lateral (two quadrants intermediate). A total of 613 cross-sections were analyzed in 14 left anterior descending, six left circumflex, and ten right coronary arteries. Plaque distribution was found to be concentric in 321 (52.4%) and eccentric in 292 (47.6%) cross sections. Of all eccentric plaques, 184 cross sections were oriented toward the myocardial side (62.6%) compared to only 54 toward the epicardial side (17.3%) and 54 in the 2 lateral quadrants (19.5%, P<0.001). No difference in plaque area (6.75+/-2.70 vs. 6.76+/-2.60 mm(2)), vessel area (15.28+/-4.73 vs. 15.35+/-4.40 mm(2)), or plaque thickness (1.26+/-0.37 vs. 1.25+/-0.43 mm) was noted between myocardial or epicardial plaques. These results suggest that atherosclerotic plaques develop more frequently on the myocardial side of the vessel wall, which may relate to lower shear stress. However, plaque size is similar on the epicardial and myocardial side.

Aged↗
PubMed2005

The cerebellum's involvement in the judgment of spatial orientation: a functional magnetic resonance imaging study.

A functional magnetic resonance imaging (fMRI) study was conducted to integrate the clinical observations of the impaired judgment of spatial orientation of cerebellar patients with recent theoretical discoveries about the role of the cerebellum in cognitive functions. Ten normal healthy male right-handed Chinese postgraduates consented to participate in this study. The experimental task employed was a modified version of Benton's Judgment of Line Orientation Test, administered in a blocked fMRI study. The findings indicated activation of the cerebellar regions, the Hemisphere Lobules IV, VI and Crus I, while the subjects were performing the experimental task of the judgment of the orientation of lines. Furthermore, cortical regions were activated, including the bilateral precuneus (BA 7), the extrastriate regions (BA 19), and the bilateral prefrontal regions (BA 9, 10, 44, 46). The imaging data confirmed that the activity of the cerebellum is associated with judging spatial orientation. The theoretical and clinical implications of the findings are discussed.

Adult↗
PubMed1998

Isotropic visual field effect on spatial orientation and egocentric localization.

The aim of this paper is to demonstrate the presence of a similar visual field effect on both spatial orientation and egocentric localization. A first experiment explored an orientation task (Visually Perceived Vertical or VPV determination) and compared the effects of a frame inclined either in the midfrontal plane (in this condition subjects assessed roll VPV) or in the median plane (subjects assessed pitch VPV) or in both combined planes (subjects assessed both roll and pitch VPV). A second experiment compared the frame effects specified above to the frame effect observed in an egocentric localization task (Visually Perceived Eye Level judgment) performed with a frame slanted in the median plane. The results showed that angular frame variations from -15 to +15 deg result in the same psychometric function for both orientation and localization tasks. In each experiment, correlations showed that individual differences occur in relation to an overall sensitivity to the visual field. Individual sensitivity may be accounted for by a ratio of visual to graviceptive information which remains constant whatever the perception plane (midfrontal or median plane) and whatever the task (spatial orientation or localization).

Adult↗
PubMedDate not supplied

Auditory localization for spatial orientation.

The use of three-dimensional auditory technology that provides localization of auditory cues presented through headphones is proposed as a means of providing supplemental information to pilots on the spatial orientation of an aircraft. This technique shows promise for reducing accidents due to spatial disorientation associated with high visual load. A study was conducted using United States Air Force pilots as subjects to determine desirable¿ cue characteristics for accurately localizing auditory cues using this technique. The study examined the use of 9 different cue types at each of 2 frequency levels. It was found that the accuracy of subjects' localization of cues in elevation was greatly enhanced by the use of multidimensional cues that provided redundant elevation information through varying frequencies and distance from the horizon cues in addition to the inherent spatial location information. Trade-offs in azimuth localization accuracy and response time were noted, however. Recommendations are made for further developing and investigating this technique for the aircraft spatial orientation task.

Accidents, Aviation↗
PubMed1993

[Losing your way in the nursing home: spatial orientation from an architectural viewpoint. A review].

Many elderly with senile dementia living in an old people's home or nursing home have problems with spatial orientation and finding their way. The same holds true for confused and disturbed elderly who still live at home. To a large extent these problems result from cognitive and perceptual impairments. However, another important and often underestimated factor is the influence of the built environment. The design of many buildings and outdoor spaces offers insufficient environmental support for route-learning, route-finding and topographical memory, which promotes disorientation. Disorientation is enhanced by repetition of identical units, little differentiation in form, colour and material, and a lack of places with striking perceptual characteristics. This review of the literature on spatial orientation of the frail elderly focuses on dementia patients. It turns out that many guidelines can be offered to reduce spatial disorientation, such as a clear layout of the building, clear functions of spaces and places, adequate contrasts of forms and colours, personalization of places and application of the so called Gestalt Laws. However, empirical research to evaluate the effects of application of these guidelines is still scare.

Aged↗
PubMed2005

Spatial orientation in echolocating harbour porpoises (Phocoena phocoena).

Studies concerning the echolocation behaviour of odontocetes focus mainly on target detection and discrimination, either in stationary animals or in animals approaching a specific target. We present the first data on the use of echolocation for spatial orientation or navigation. Synchronised video and high-frequency recordings were made of two harbour porpoises trained to swim from one position to another across an outdoor pool in order to correlate swimming and echolocation behaviour. Both porpoises showed a clear range-locking behaviour on specific positions near the end of the pool, as indicated by a decrease in click interval with decreasing distance. The decrease in click interval followed the two-way-transit time, which is the time interval between the outgoing click and the received echo from the focal object. This suggests that the porpoises used focal objects as landmarks. The lag time, defined as the time between the arrival of an echo from a landmark and the emission of the next click, was task specific. The lag time was longer for difficult tasks (26-36 ms) and shorter for simpler tasks (14-19 ms), with some individual differences between the two animals. Our results suggest that echolocation by odontocetes is used not only for target detection, localisation and classification but also for spatial orientation.

Animals↗
PubMed1975

Response of the elasmobranch utricle to maintained spatial orientation, transitions and jitter.

1. The spike discharges of single first order afferents from the utricle were recorded in the isolated head of the guitarfish and tested for responses to maintained spatial orientation, to transitions and to a small positional jitter representing natural perturbations. Sensitivity to maintained orientation is referred to as "tonic", and to transitions and jitter as "phasic". 2. Most responsive cells were either phasically, or phasically and tonically sensitive. A few were exclusively tonic. Tonic responsiveness implied that maintained orientation was associated with a stationary discharge which differed from one position to another; it sometimes differed also from one station to another at the same position. Transitions from one position to another evoked a rate change that later adapted to the level of the tonic response. Opposite transitions evoked rate changes in the opposite sense. The phasic rate change was usually larger for transitions that increased the rate. Many units were non-responsive. The prevalence of phasic over tonic sensitivity is stressed, and the remarkable heterogeneity of utricular afferents confirms that the macula is not uniform, probably coding a wide variety of head accelerations. 3. The jitter increased the ongoing scatter of intervals and binrates, changing, complicating, or abolishing their periodicity. The jitter could influence the effects of maintained orientation, increasing, decreasing, inverting or even revealing directional sensitivity. It could also force previously independent units into an orientation-dependent correlation; hence, between-cell correlation is potentially useful in coding of spatiel orientation. Naturally occurring perturbations may sonstitute a significant issue of normal operation. 4. Certain afferents from the horizontal semicircular canal showed a slow tonic response to maintained spatial orientation.

Action Potentials↗
PubMed2005

Transient hypobaric hypoxia improves spatial orientation in young rats.

To achieve a better understanding of learning and declarative memory under mild transient stress, we investigated the effect of brief hypobaric hypoxia on spatial orientation in rats. Young male Wistar rats aged 30 days were exposed for 60 min to hypobaric hypoxia, simulating an altitude of 7,000 m (23,000 ft) either shortly prior to attempting or after mastering an allothetic navigation task in the Morris water maze with a submerged platform. The post-hypoxic group performed significantly better in the navigation task than the control animals (the mean difference in escape latencies was 11 seconds; P=0.0033, two-way ANOVA with repeated measures, group x session). The experimental group also achieved a remarkably higher search efficiency (calculated as a percentage of successful trials per session), especially during the first four days following hypoxic stress (P=0.0018). During the subsequent training, the post-hypoxic group performed better than the control animals, whilst the efficiency levels of both groups progressively converged. Spatial memory retention and recall of well-trained rats were not affected by the transient hypobaric hypoxia. These results indicate that brief hypobaric hypoxia enhances rats' spatial orientation. Our findings are consistent with several studies, which also suggested that mild transient stress improves learning.

Adaptation, Physiological↗
PubMed1991

[Control of gaze and locomotion by spatial orientation].

We reported a new theory for daily vestibular functions which advocates top-down regulation of posture and gaze by supposing the coordinates in the brain. The hypothesis consists of three principles; first, the vestibular system is primarily a sensory system to detect spatial orientation; second, multisensory integrations reconstruct three-dimensional coordinates in the brain, which ascertain spatial orientation; third, daily behaviours like gazing or walking are controlled in a feed-forward manner by programming on the coordinates in the brain. The hypothesis was useful to understand strategic differences between active and passive movements, to distinct gaze control from ocular reflexes, to apply the rules of gaze control to posture control, and to clarify the mechanism to produce motion sickness.

Fixation, Ocular↗
PubMed2005

Egocentric spatial orientation in a water maze by rats subjected to transection of the fimbria-fornix and/or ablation of the prefrontal cortex.

The acquisition of a water maze based task requiring egocentric spatial orientation in the absence of distal cues was studied in four groups of rats: animals in which the fimbria-fornix had been transected, rats that received bilateral ablations of the anteromedial prefrontal cortex, animals in which both of these structures had been lesioned, and a sham-operated control group. Isolated lesions of both the anteromedial prefrontal cortex and the hippocampus were associated with a significantly impaired task acquisition. Both of these individually lesioned groups did, however, eventually demonstrate full functional recovery by reaching the task proficiency of the sham-operated control group. In contrast, the group in which both of these structures had been lesioned failed to demonstrate full functional recovery and was severely and long-lastingly impaired when compared to all other groups. Behavioural challenges in the form of a no-platform session and two reversals of platform position demonstrated that while the sham-operated control group and the group subjected to fimbria-fornix transections in isolation utilized rather pure egocentric orientation strategies, the two prefrontally lesioned groups (and especially the combined lesion group) employed a different set of solution strategies which at least partly relied on a "circling" method. Even in the behaviour of the prefrontally lesioned groups, however, indications of a certain level of cognitive representations of the platform positions were seen. It is concluded that both the prefrontal cortex and the hippocampus contribute to the mediation of egocentric spatial orientation. Furthermore, the hippocampus is a significant and potentially irreplaceable part of the neural substrate of functional recovery of the presently studied task after prefrontal lesions--while the prefrontal cortex may play a similar role with respect to hippocampal lesions.

Animals↗
PubMed1998

Combined deficits of saccades and visuo-spatial orientation after cortical lesions.

Functionally, saccadic eye movements are closely linked to visuo-spatial orientation. Anatomically, the network of cortical areas controlling saccades also seems to be involved in spatial attention and orientation. Consequently, lesions should cause deficits in both categories. We investigated this in 34 patients with focal unilateral lesions of the posterior parietal cortex (PPC), the frontal eye fields (FEF), the supplementary motor area (SMA), or the dorsolateral prefrontal cortex (PFC). Saccadic eye movements were recorded using infrared reflection oculography. Visual hemineglect or other visuo-spatial disorders were investigated by a series of standardized paper-pencil tests. Further, the internal spatial coordinates (subjective visual vertical and subjective straight ahead) were assessed psychophysically. Depending on the site of the lesion, different patterns of deficits were identified: lesions of the PPC impaired reflexive exploration of visual space in terms of delayed and hypometric visually triggered saccades into the contralesional hemifield, related to the severity of visual hemineglect. Further, PPC lesions specifically affected basic functions of the perceptual analysis of space, such as the internal spatial coordinates and spatial constancy across saccades. The latter was tested by applying visual double-step stimuli, where saccade-related extraretinal information had to be taken into account for achieving spatial accuracy. Frontal lesions left these functions intact. FEF lesions, however, impaired systematic intentional exploration of space, thus causing an exploratory-motor type of visual hemineglect. Prefrontal (PFC) lesions impaired the working memory for saccade-related spatial information, and SMA lesions affected temporal properties such as the timing of saccadic sequences, but did not cause specific visuo-spatial deficits. In conclusion, patients with frontal or parietal cortical lesions often exhibit combined saccadic and visuo-spatial disorders, most of which are topically specific.

Brain Diseases↗