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Results for “Spatial orientation”

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At least 127 records · Page 7Linked to original sources
PubMed2005

Functional consequences of retinal degeneration in spatial orientation in C3H wild type and Lurcher mutant mice.

Lurcher mutant mice represent a model of genetically determined olivocerebellar degeneration. In the C3H strain there is also hereditary retinal degeneration. The aim of this work was to assess, whether the retinal degeneration influences spatial orientation and results of the spatial learning tasks. Two experiments in the Morris water maze were arranged. First, mice learned to find a platform position, which was linked to two labels on the periphery of the maze. In the second experiment the platform was removed and swimming velocity and preference of central or peripheral zone of the maze were assessed. Presence of the retinal degeneration was detected histologically. Both Lurcher mutant and wild type mice that exhibited long latencies in the first experiment were affected with the retinal degeneration, while animals that performed the trial well, had normal retina. Swimming velocity was not changed substantially. The maze exploration strategy was different in mice with and without the retinal degeneration.

Animals↗
PubMed1989

Event-related potentials, spatial orienting, and reading disabilities.

Event-related potentials (ERPs) were used to investigate the effects of visual-spatial orienting on selective neural processing in boys with learning disabilities. Twenty-seven 8-12 year old boys were classified into four groups depending on whether or not they had a reading disability or attention deficit disorder. Event-related potentials were recorded over the left and right occipital, central, and frontal cortical regions. The behavioral task required the subjects 1) to rapidly switch their attention from the center to the periphery of the visual field (spatial component), and 2) to selectively respond to a target versus a nontarget flash when the target was presented in the relevant visual field (nonspatial component). The amplitude of two ERP components was enhanced in response to relevant as compared to irrelevant stimuli. The enhancement of an early negative occipital-central component, which peaked 180-200 ms following targets (N1), indicated that selective neural processing associated with spatial attention could be switched in 600 ms. This enhancement of N1 was greater in boys with than without a reading disability, which implies that reading disability is associated with enhanced spatial attention. The enhancement of a later positive component, which peaked 300-340 ms following targets (P3), suggested that nonspatial target selection was reduced in boys with a reading disability, particularly over the left occipital hemisphere. Target relevance and reading disability also influenced trial-to-trial variability in the ERP waveform. The effects of reading disability on event-related potentials did not vary as a function of attention deficit disorder, indicating that these two disorders are distinct.

Arousal↗
PubMed2000

Longitudinal age-related changes in motor activities and spatial orientation in CD-1 mice.

Female CD-1 mice were evaluated on three occasions over a nineteen month span in tests of exploration, motor coordination, and spatial orientation in a water maze. Aging decreased motor activity and exploration of specific environmental stimuli found in a hole-board and in a T-maze. Age-related deficits were also found in three motor coordination tasks (inclined grid, coat-hanger, and round bridge) and during retention but not acquisition of the hidden platform version of the water maze task. Performance on some motor coordination tests was linearly correlated with either motor activity or exploration, implying the existence of similar neurobiological pathways responsible for these age-related changes.

Aging↗
PubMed1995

Spatial orientation of the reentrant circuit of idiopathic left ventricular tachycardia.

In 6 patients with idiopathic left ventricular VT, the spatial orientation of the reentrant circuit was estimated from the results of transient entrainment of VT with rapid pacing at different sites. The entrance to the area of slow conduction was located toward the outflow tract, whereas the exist was located at the apicoposterior area of the left interventricular septum.

Adult↗
PubMed1984

Spatial orientation in weightlessness and readaptation to earth's gravity.

Unusual vestibular responses to head movements in weightlessness may produce spatial orientation illusions and symptoms of space motion sickness. An integrated set of experiments was performed during Spacelab 1, as well as before and after the flight, to evaluate responses mediated by the otolith organs and semicircular canals. A variety of measurements were used, including eye movements, postural control, perception of orientation, and susceptibility to space sickness.

Acceleration↗
PubMed2005

Effects of visual flow display of flight maneuvers on perceived spatial orientation.

Postural responses were utilized as measures of the effectiveness of a wide-angle visual flow display in determining perceived spatial orientation (SO). The general experimental setup included a 150 degrees x 34 degrees wide-field display showing flight over computer-generated ground with horizon. Simulated roll maneuvers on this display induced postural sway in the observer that was registered by a head-tracker system. Two experiments with 16 participants in each investigated the effects of visual flow, display exclusions in the central visual field, and display extensions into the visual periphery. Clear vestibular and proprioceptive suppression effects were demonstrated on postural sway with the inclusion of visual flow of forward ego motion in roll maneuvers. Compared with the full view, up to 20 degrees x 20 degrees central field omission either did not reduce the effect or reduced the effect but, frequently, only moderately. Limiting the display area to 45 degrees in the horizontal dimension reduced display effectiveness significantly, whereas a 105 degrees area did not, compared with the full view. Utilizing postural responses as indications of visual display resonance with our SO mechanism, actual or potential applications of this research include the design of an interface integrating flight-adapted visual flow to counteract or reduce pilot spatial disorientation.

Adult↗
PubMed1994

ERP and RT signs of a rightward bias for spatial orienting in a split-brain patient.

Neuropsychological data have shown that the two cerebral hemispheres differ in the control of spatial attention. The present study investigated hemispheric asymmetries and visuomotor integration in a split-brain patient and three control subjects. Simple reaction times (RTs) and event-related potentials (ERPs) were recorded to lateralized stimuli presented at different eccentricities in the left and right visual hemifields. Both electrophysiological and behavioural data showed that, unlike controls, the split-brain patient showed a strong rightward attentional bias resulting in shorter RTs and larger P300 potentials to stimuli falling in the rightmost space. Furthermore, ERPs also showed that while the RH has a bilateral control of visual space, the LH spatial orienting capability is most restricted to the contralateral hemifield.

Adult↗
PubMed1989

Vestibular contribution to spatial orientation. Evidence of vestibular navigation in an animal model.

To determine if animals are capable of utilizing vestibular sensory input for spatial orientation, a six-arm radial maze with a rotating central turntable was constructed. Sprague-Dawley rats were trained on this apparatus by rotating them without visual, auditory, or olfactory cues. Animals were required to locate a reward (located in a constant position relative to the starting position) following random rotations varying from 0 to +/- 360 degrees, growing progressively larger in 60 degrees increments. Normal rats (N = 10) showed a steady improvement in performance over the training and testing period. Bilateral labyrinthectomy (N = 5) produced a profound decrement in that performance (p less than 0.001). When visual cues were added, labyrinthectomized animals improved their performance, but remained significantly below that of normal animals without visual cues (p less than 0.001). Normal animals allowed to use visual cues showed no improvement over their performance without visual cues. The results indicate that rats can utilize vestibular sensory information for navigational purposes. In fact, under these experimental conditions, rats are more successful in utilizing vestibular sensory input for navigation than visual cues.

Animals↗
PubMed2005

Mice with the deleted neurofilament of low molecular weight (Nefl) gene: 2. Effects on motor functions and spatial orientation.

Mice with a null mutation of the Nefl gene were compared with normal controls in tests of motor activity, equilibrium, and spatial orientation. Despite a normal capacity to ambulate, NFL -/- mice had fewer rears in an open field, crossed fewer segments on stationary beams, and fell more frequently when suspended on a horizontal bar. In addition, the distance swum before reaching the escape platform was greater in NFL -/- mice than in controls during acquisition of place learning in the Morris water maze at the start of training. The motor impairments were linearly correlated with increased cytochrome oxidase activity seen in cerebellum and brainstem. These results indicate that, as early as 6 months, depletion of the NFL protein is sufficient to cause mild sensorimotor dysfunctions and spatial deficits, but without overt signs of paresis.

Amyotrophic Lateral Sclerosis↗
PubMed1991

Spatial orientation of VOR to combined vestibular stimuli in squirrel monkeys.

The interaction of angular and linear stimuli produces a complex alignment of spatial orientation and the VOR. This phenomenon was studied by measuring three dimensional eye movements in 6 squirrel monkeys during centrifugation in the dark. The axis of eye rotation was always aligned with gravity and with the spinal axis of the upright monkeys. The erect monkeys were oriented such that they were either facing toward the direction of motion or were facing away from the motion. Angular velocity trapezoids were utilized as the motion stimuli with a ramp acceleration of 10 degrees/s2 to a constant velocity of 200 degrees/s. This yields a final centripetal acceleration of 1 g. The orientation of centripetal acceleration dramatically altered the VOR by changing the axis of eye rotation, the peak value of slow phase eye velocity, and the time constant of per-rotary decay. The axis of eye rotation always tended to align with gravito-inertial force, the peak value of slow phase eye velocity was greater when the monkey faced the motion than when it faced away from the motion, and the time constant of decay was smaller when the monkey faced the motion than when it faced away from the motion. These findings were statistically significant (p less than 0.05) and were consistent across all monkeys. The data also indicate that the VOR may be separated into two reflexes, a linear reflex and a rotational reflex. The linear reflex decays as the axis of eye rotation aligns with gravito-inertial force (GIF). These results indicate that GIF is resolved into two components: one representing an internal estimate of linear acceleration and one representing an internal estimate of gravity.

Acceleration↗
PubMed1998

[Effects of spatial orientation on attention reaction time during pointing movement towards visual direction].

In the present study, it was consequently proposed to investigate how the spatial orientation of attention made by the explicit and implicit components of advance information, affected the reaction time (RT) performances. Subjects performed a simple RT task with an orientation cue and two choice RT situations, the one with a neutral cue and the other with a primed cue. The motor task to be performed consisted of pointing towards a visual target. The mechanisms involved in the orientation of attention were studied on the one hand by analysing the effects of the preparatory signal, which explicitly oriented the subjects' attention towards the forthcoming target position, and on the other hand, by examining whether the reinforced probability of warning stimulus(WS) and imperative stimulus (IS) being compatible affected the subjects' performances, i.e., whether they detected and made use of the information implicitly conveyed that there existed a bias in favour of the probability that IS would appear in the direction predicted by WS. The results of this study show that the subjects shortened their RTs by using both the explicit(auditory) and the implicit(probability-related) information with which they were provided prior to performing the movement. These data on the effects of the oriented auditory signal on the reaction times indicate that in our experiments, by orienting their attention depending on the position of the stimuli, the subjects were able to reduce their reaction times. The significant correlation found to exist here between the level of probability associated with the position of the WS and the choice RT values indicates that also the implicit information as to the WS-IS compatibility was taken into account by the subjects in all the situations.

Adult↗
PubMed1973

Spatial orientation in man: effects of left, right, and bilateral posterior cerebral lesions.

Men with chronic, penetrating missile wounds of the brain were examined with two `spatial' tasks: a visually-guided stylus maze and a locomotor map-reading task. Men whose lesions involved the posterior part of the right cerebral hemisphere were significantly worse than those with left posterior lesions at stylus maze-learning. On the locomotor task, however, a highly significant deficit was found in the group of men with bilateral posterior cerebral lesions, while those with unilateral lesions of either hemisphere and those with bilateral frontal lesions were unimpaired. The contributions of the two cerebral hemispheres to the analysis of spatial information are discussed in the light of these results and it is suggested that, while the right hemisphere has a special role in the perception of space, it does not bear exclusive responsibility for the maintenance of spatial orientation.

Brain Injuries↗
PubMed2005

Echolocating bats can use acoustic landmarks for spatial orientation.

We investigated the echolocating bat's use of an acoustic landmark for orientation in a complex environment with no visual information. Three bats of the species Eptesicus fuscus were trained to fly through a hole in a mist net to receive a food reward on the other side. In all experiments, the vocal behavior of the bats was recorded simultaneously using a high-speed video recording system, allowing for a 3D reconstruction of the flight path. We ran three types of experiments, with different spatial relations between the landmark and net hole. In the first experiment, the bat's behavior was studied in test trials with the landmark placed 10 cm to the left of the net opening; between test trials, the positions of the net opening and landmark were moved, but the spatial relationship between the two remained fixed. With the landmark adjacent to the net opening, the bats quickly found the hole. In the second experiment, bats were tested in control trials in which the landmark was moved independently of the hole, breaking the established spatial relationship between the two. In control trials the bats repeatedly crashed into the net next to the landmark, and inspected the area around it. In the final experiment, the landmark was removed altogether from the set-up. Here the bats spent more time per trial searching for the net opening with an increased number of inspections as well as crashes into the net. However, over the course of a test day without the landmark, bats reduced the time spent per trial and focused inspections and crashes around the hole. The behavioral data show for the first time that the echolocating bat can learn to rely on an acoustic landmark to guide spatial orientation.

Animals↗
PubMed2006

[Spatial orientation memory: evaluation in patents with Alzheimer disease and temporal lobe epilepsy].

Experimental studies have identified pyramidal cells in hippocampus in rats with participation in the spatial orientation memory (SOM), which are named location cells. This study had the purpose to adapt a test based in these experiments in order to check the performance of SOM and the participation of hippocampus into SOM in patients with mesial temporal sclerosis (MTS). The research was divided into two studies: the first one the test was adapted, and in order to check its capacity to investigate the deficits of SOM, it has applied in groups of 10 (ten) subjects, one group with patients that have Alzheimer disease and the other one with healthy elderly (p<0.001). The second study has evaluated the participation of hippocampus into SOM in 43 patients (23 with mesial temporal sclerosis (MTS) and 20 submitted to selective amygdala hippocampectomy (SAH)) and 23 healthy volunteers with p<0,05 between MTS and SAH and between controlled and SAH. It was shown that the test of SOM is suitable to evaluate deficits, but it seems the SOM is not a specific function of human hippocampus.

Adult↗
PubMed1995

Active control in interrupted dynamic spatial orientation: the detection of orientation change.

Gibson (1966, 1979) suggested that an important property of perception is that the observer is active. Two experiments were conducted to examine the benefits of active observation in determining dynamic spatial orientation. Subjects were presented with displays simulating locomotion through a three-dimensional environment. Active observers continuously controlled locomotion, whereas passive observers viewed the display. During the trial, the display was blacked out for a brief period, followed by a static image that was at either the correct or the incorrect orientation following the blackout. Subjects were required to indicate whether they were positioned at the correct extrapolated orientation. The presence or absence of orientation change, the type of change (changes in rotation about the depth axis [roll], horizontal axis [pitch], or forward translation), the duration of the blackout, and the consistency of change were varied. In addition, the experiments used either a compensatory or a pursuit tracking task. Active observers had greater sensitivity than did passive observers in detecting a change for both tracking tasks. Subjects in both experiments exhibited greater sensitivity in detecting inconsistent changes (relative to consistent changes), suggesting that the dynamics specified by optical flow were incorporated in extrapolated orientation. In addition, sensitivity decreased with an increase in blackout duration. The results are discussed in terms of an extrapolation model of perception that incorporates the responses executed by active observers.

Attention↗
PubMed2002

The importance of head-free gaze control in humans performing a spatial orientation task.

The present study aimed at investigating how a specific instruction concerning gaze orientation, which involved active head motion, could influence the performance of human subjects in a self-controlled whole-body rotation task in the dark. Subjects were seated on a mobile robotic chair that they controlled using a joystick. They were asked to perform 360 degrees rotations while maintaining, when possible, the gaze on the estimated position of an earth-fixed target. Subjects performed better when gazing at this target than when no target was shown. Furthermore, performance was significantly related to head stabilization in space. The results reveal the importance of head-free gaze control for spatial orientation in so far as it may involve spatial reference cues and sensory signals of different modalities, which may be beneficial to self-motion perception.

Adult↗