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Results for “Spatial orientation”

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PubMed1981

Effects of commune-internal migration in Finland on the spatial distribution of population and on dwelling house utilization.

"The article is based on a programme of research which has been pursued for some years with the purpose of describing the extent and spatial orientation of commune-internal migration [in Finland], a topic about which very little has previously been known, relating this form of migration to total population movement and to dwelling house requirements and utilization. The analysis yields information on the dynamics of population changes occurring in areas on the margins of permanent settlement, while at the same time taking into consideration the effects of regional and in particular housing policy decisions upon the spatial distribution of population."

Demography↗

PubMedDate not supplied

Spatial learning on the Morris Water Maze Test after a short-term paradoxical sleep deprivation in the rat.

Twelve rats were deprived of paradoxical sleep (PS) for eight hours using the small platform method. PS-deprived and control rats then learned either the standard allocentric version (using external cues) of the Morris Water Maze (MWM) or a delayed alternation version (changing the platform location between trials: MWM(DA)). Overall, rats learning the MWM(DA) made more quadrant entries than rats learning the allocentric version. Compared to other rats, PS-deprived rats crossed more quadrants only in the MWM(DA). These results show that MWM(DA) is a more complex task to learn and is more vulnerable to PS deprivation than allocentric spatial orientation. Since delayed alternation is dependent upon frontal structures, we propose that tasks involving the frontal cortex are more sensitive to short-term PS deprivation than tasks related to hippocampal structures.

Animals↗

PubMed1981

The distribution and orientation of serotonin fibers in the entorhinal and other retrohippocampal areas. An immunohistochemical study with anti-serotonin antibodies in the rats brain.

The serotonin (5-hydroxytryptamine; 5-HT) innervation of the retrohippocampal region (subiculum, pre- and parasubiculum, area 29e, medial and lateral entorhinal area) in the rat brain has been examined with antibodies against 5-HT used in combination with fluorescence histochemistry. Analysis of consecutive sections cut in the coronal, sagittal, and horizontal planes revealed a widespread distribution of 5-HT immunoreactive fibers throughout the retrohippocampal region. This innervation was with regard to the morphological characteristics of the 5-HT fibers, their density and their spatial orientation. On the basis of morphological criteria, four different types of 5-HT positive processes were distinguished: (a) fine, convoluted fibers with small (approximately 0.5-0.8 micron), round and evenly spaced varicosities: (b) fine fibers with small elongated, irregularly distributed varicosities; (c) thick, possibly myelinated fibers, and (d) a terminal plexus with large (5-10 micron), irregularly spaced varicosities. Analysis of the laminar distribution of the 5-HT fibers showed that whereas all layers contain 5-HT positive fibers, the molecular layer was the most densely innervated. The 5-HT fibers were found to be oriented both parallel and transverse to the longitudinal axis of medial and lateral entorhinal area. This grid-like arrangement was less pronounced in the presubiculum. Although the 5-HT innervation of the retrohippocampal region was found to be dominated by a widespread and apparently diffuse pattern, several areas contained dense clusters of preterminal 5-HT processes: area 29e, dorsal presubiculum (layer II), lateral entorhinal area (layer III and ventral layer II) and the transitional zone of the ventral entorhinal area. The 5-HT fibers were found to enter the retrohippocampal region primarily by three different routes; from the ventral and dorsal aspects and from the piriform and lateral neocortex (via the perirhinal area). Most of the fibers enter the region by the ventral route and these were found to ascend in all layers but predominantly in layer I. The location of the 5-HT cells giving rise to the innervation of the entorhinal area was studied by combining retrograde transport of fluorescent tracers with immunohistochemistry on the same tissue section. Both ipsi- and contralaterally located cells in the dorsal and median raphe nuclei were found to project to the entorhinal area. Most, but not all, of these retrogradely labeled cell bodies also contain 5-HT immunoreactivity.

Animals↗

PubMed2000

Continuous place avoidance task reveals differences in spatial navigation in male and female rats.

A new place navigation test was used to estimate the spatial orientation abilities of male and female rats. Animals had to avoid a room frame defined area on a rotating arena, entering of which was punished by mild footshock, i.e. rats had to avoid the same place in the room but different parts of the floor, which was rotated through the punished zone. Because of the rotation of the arena (one revolution per min), animals could not rely on intramaze cues and only extramaze landmarks could be used for accurate navigation. During 8 consecutive days rats were exposed to daily 40-min sessions, consisting of 20-min acquisition and 20-min extinction (shock discontinued). The position of the punished sector centered around one of the four mutually perpendicular azimuths was daily changed in a predetermined sequence. The results showed no male female differences during acquisition and better performance of males during extinction. The performance of females was not affected by estral cycle-related hormonal changes. The findings are discussed in the light of controversial results of research into sex differences in spatial abilities.

Animals↗

PubMedDate not supplied

[Effect of rotation and vibration on orientation in man in relation to the gravitational vertical].

The man's ability to get oriented in relation to the gravitational vector was investigated. The test subjects were exposed either to rotation in 1 m arm centrifuge or tilting in a chair. They were simultaneously exposed to total-body vertical vibration of 20 Hz. As the exposure continued, the ratio of the perceived vertical (in the absence of visual keys) and the apparent body position changed significantly. It is concluded that the tests used to evaluate the pilot ability for spatial orientation should include evaluations of the subjective vertical and body position relative to the gravitational vector. The tests should be performed during exposures to simulated dynamic flight factors.

Aerospace Medicine↗

PubMed2002

Modulation of spatial attention by fear-conditioned stimuli: an event-related fMRI study.

Stimuli that signal threat can capture subjects' attention, leading to more efficient detection of, and faster responses to, events occurring in that part of the environment. In the present study we explored the behavioural and anatomical correlates of the modulation of spatial attention by emotion using a fear conditioning paradigm, combined with a covert spatial orienting task. Reaction times for the detection of a peripheral target, which was preceded by brief (50ms) presentations of the visual conditioned stimulus (CS+) in either the same or opposite visual field, showed an interaction between stimulus emotionality and attention shifts. We used event-related functional magnetic resonance imaging (fMRI) to characterise the associated neural responses. Consistent with previous studies, conditioning-induced enhanced responses were observed in the amygdala and extrastriate visual cortex. The modulation of spatial attention by a conditioned stimulus was associated with enhanced activity in regions of frontal and parietal cortices previously implicated in spatial attention, as well as in the lateral orbitofrontal cortex (lOFC).

Amygdala↗

PubMed2002

Advantages of using noncoplanar vs. axial beam arrangements when treating prostate cancer with intensity-modulated radiation therapy and the step-and-shoot delivery method.

PURPOSE: The focus of this work was to compare noncoplanar beam arrangements used for intensity-modulated radiation therapy (IMRT) step-and-shoot delivery to several axial beam arrangements used in the treatment of clinically localized prostate cancer. METHODS AND MATERIALS: A 5-field coronal crossfire beam arrangement was developed for IMRT with the objective of improving upon the rectal and bladder dose-volume histograms obtained using 5-, 7-, and 9-field axial beam arrangements. Additionally, a modified 7-field crossfire technique was developed yielding improved dose distributions. The average values of dose-volume histograms and the time for treatment delivery were evaluated for all plans for 10 randomly chosen patients. RESULTS: Both crossfire IMRT techniques exhibited a 15-25% decrease in dose to the hottest 10% and 20% of the rectum relative to all three axial IMRT techniques. The 5-field crossfire orientation yields slightly higher bladder doses when compared to the other techniques. In selected cases, the 7-field crossfire beam arrangement demonstrates decreased dose to the bladder when compared to all three axial techniques. A mean delivery time of 14 to 17.5 min is noted for the noncoplanar arrangements after positioning and localization. CONCLUSIONS: A technique is described that allows additional normal tissue sparing during dose escalation to the prostate during IMRT delivery. This technique takes advantage of the spatial orientation between the prostate, rectum, and bladder. With patient setup and target localization time aside, a mean treatment time of 14 to 17.5 min allows the delivery of the crossfire plans to conform to standard treatment times.

Humans↗

PubMed2000

Repetition priming reveals sustained facilitation and transient inhibition in reaction time.

Reaction time (RT) in a detection or a location discrimination task increases when a target is repeatedly presented at the same location (inhibition), whereas RT decreases in feature (color or orientation) discrimination tasks (facilitation; Y. Tanaka & S. Shimojo, 1996a). Here, the time course of inhibition and facilitation was examined, using a repetition priming paradigm. Results indicate that inhibition occurred only in the immediately successive trial, whereas facilitation accumulated over several trials with location repetition. Moreover, inhibition and facilitation occurred in a task-relevant manner: Detection-location discrimination tasks produced transient RT increase, whereas feature discrimination tasks produced cumulative RT decrease. These results suggest a functional dissociation between spatial orienting and feature analysis, as well as top-down modulations by tasks leading to different types of visual memory.

Adult↗

PubMed2003

Time, space and hippocampal functions.

The hippocampus is one of the most researched structures of the brain. Studies of lesions in humans, primates and rodents have suggested to some that the primary role of the hippocampus is to act as a temporary memory buffer which is required for the consolidation of long-term memory. The famous case study of patient H.M., in particular, seemed to suggest that the hippocampus was of crucial importance for memory formation. However, recordings of single neurons in freely moving rodents did not support this notion. In such recordings, neurons were found that were active predominately when the animal passed through a particular area in space. Consequently, these neurons were termed 'place cells' and a theory was developed that suggested that the hippocampus acts as a 'cognitive map' that is required for spatial orientation. It was then found that H.M. had significant damage to his temporal lobes that included the amygdala, rhinal cortices, and other areas. Further case studies and selective hippocampal lesions in primates resulted in much milder amnestic symptoms, and lesions of defined cortical areas in the temporal lobes showed that a number of functions previously attributed to the hippocampus were in fact linked to these areas. Further analysis of neuronal activity in the hippocampus showed that not only is spatial information represented there, but also additional information, such as speed of movement, direction of movement, match or non-match detection, olfactorial identification, and others. In addition, it was found that selective lesions of the hippocampus in rodents impaired spatial navigation and memory formation only mildly. Only simultaneous lesions of several cortical areas in conjunction with the hippocamus could reproduce the impairments and symptoms that were previously thought to be observed after hippocampal lesions alone. In conclusion it is proposed that information processing and memory formation is shared by several brain areas that act as a functional system. This review presents evidence from many different studies that the hippocampus is part of this system and plays a supportive role in associating complex multimodal information and laying down new memory traces. In addition, the concept of allocating specific functions (such as the development of a cognitive map) exclusively to the hippocampus is rejected.

Animals↗

PubMed2006

Crossing the pillars of Hercules: the role of spatial frames of reference in error making.

This paper introduces a perspective accounting for errors that may occur as a result of the human interaction with the three-dimensional (3D) space. Particularly, we are interested in errors that are caused by cognitively crossing the boundary between peripersonal and extrapersonal space. Several behavioural, neurophysiological, and neuropsychological perspectives are reviewed in order to develop the theoretical framework on which our ideas are founded. We argue that cognitively crossing the boundary implies switching from one frame of reference to another, which, as a consequence, implies specific costs. The results of five experiments (overall involving 76 participants) support our hypothesis, suggesting the existence of different action-oriented spatial frames of reference.

Adult↗

PubMed2000

Canal-otolith interactions after off-vertical axis rotations I. Spatial reorientation of horizontal vestibuloocular reflex.

We examined the three-dimensional (3-D) spatial orientation of postrotatory eye velocity after horizontal off-vertical axis rotations by varying the final body orientation with respect to gravity. Three rhesus monkeys were oriented in one of two positions before the onset of rotation: pitched 24 degrees nose-up or 90 degrees nose-up (supine) relative to the earth-horizontal plane and rotated at +/-60 degrees /s around the body-longitudinal axis. After 10 turns, the animals were stopped in 1 of 12 final positions separated by 30 degrees. An empirical analysis of the postrotatory responses showed that the resultant response plane remained space-invariant, i.e., accurately represented the actual head tilt plane at rotation stop. The alignment of the response vector with the spatial vertical was less complete. A complementary analysis, based on a 3-D model that implemented the spatial transformation and dynamic interaction of otolith and lateral semicircular canal signals, confirmed the empirical description of the spatial response. In addition, it allowed an estimation of the low-pass filter time constants in central otolith and semicircular canal pathways as well as the weighting ratio between direct and inertially transformed canal signals in the output. Our results support the hypothesis that the central vestibular system represents head velocity in gravity-centered coordinates by sensory integration of otolith and semicircular canal signals.

Algorithms↗

PubMed1986

Characterization of left ventricular chamber distortion: alterations in cavity shape and orientation in mitral stenosis.

Distortion of the left ventricular (LV) chamber silhouette was identified in 28 patients with mitral stenosis (MS) by disparity between normally identical chamber volumes calculated independently from the frontal (AP) and lateral (LAT) views of biplane cineangiograms (AP end diastolic volume 157.8 +/- 10.0 ml, LAT end diastolic volume 115.6 +/- 7.2 ml, p less than .001). Similar systematic disparity was observed in estimates of end systolic volume in these views. While no directional difference in ejection fraction was found, identical (+/- 10%) AP and LAT measurements were obtained in only 36% of patients, indicating poor reproducibility of the estimate of LV function between single radiographic views. A technique was also devised for determining the spatial orientation of the LV long axis (mid mitral valve to apex) from biplane cineangiograms; this axis was shown to intercept the frontal plane at an angle of 50.9 +/- 2.4 degrees in 12 subjects with normal LV anatomy and 36.1 +/- 4.5 degrees in seven patients with MS, indicating that the long axis was rotated posteriorly toward alignment with the frontal plane in the latter group. The presence and magnitude of LV chamber distortion was clearly related to the degree of angiographically estimated right ventricular dilatation. Implications of these observations, particularly with reference to the estimation of single plane LV volume characteristics in patients with MS, are discussed.

Angiocardiography↗

PubMed1999

Spatial working memory and reference memory of Brown Norway and WAG rats in a holeboard discrimination task.

To determine whether working memory (WM) and reference memory (RM) represent different aspects of spatial memory, albino WAG rats and the pigmented Brown Norway rats were tested in the acquisition, retention, and reversal of spatial orientation tasks in the holeboard, which allows the simultaneous assessment of WM and RM. Putative nonmnemonic factors, such as the speed of visiting the holes or the development of a search strategy (preferred sequence of visiting the baited set of holes) were also evaluated because they might influence WM and RM performance. The WM performance of Brown Norway rats was generally worse than that of the WAG rats. The reverse was true for the RM performance. Correlation analysis supported the notion that these two measures are independent. Differences in the speed of visiting the holes and in the development of a preferred sequence of visiting the baited set of holes could not explain the strain differences in WM and RM performance. Because spatial WM and RM appear to be independent measures in the holeboard, this task could be used to investigate whether different neural substrate(s) underlie these two memory components.

Animals↗

PubMedDate not supplied

Spatial disorientation episodes among F-15C pilots during Operation Desert Storm.

Spatial Orientation (SO) under flight conditions is the accurate "integration" of sensory inputs from the dynamic aviation environment that result in safe and effective goal-oriented performance. Insidious sensory mismatches routinely occur during flight, impeding pilot performance. When this sensory dissonance occurs, if not appropriately resolved, it will result in perceived or actual errors in aircraft control that are estimated to cost the Air Force between $150 and $200M per annum in aircraft accidents. A scientific survey was created and administered to 96 F-16C combat pilots after their return from Desert Storm. The survey sought to determine where in the flight profile, and under what conditions, spatial disorientation (SD) episodes occurred. The survey consisted of multiple choice and open-ended questions. The analyses of the data revealed that visual transitions from inside to outside the cockpit (or the reciprocal) under different conditions of flight were associated with the occurrence of SD episodes. The frequency of SD episodes varied depending on visual transitions (or no visual transitions) and types of flight conditions (for example, nighttime and bad weather). This SD survey provided flight information that allowed us to direct research to those areas that were problematic during combat operations.

Accidents, Aviation↗

PubMed2004

The effect of the orientation of the noncircular radial head on elbow kinematics.

OBJECTIVE: The objective of this study was to identify the effect of radial head shape and orientation on elbow kinematics in the otherwise intact elbow. DESIGN: Biomechanical study, analyzing simulated active motion of cadaveric arms. BACKGROUND: A discrepancy exists between the noncircular anatomy of the radial head and radial head prostheses. The effect of radial head shape is unknown. METHODS: Kinematic effects of radial head shape were tested in six fresh-frozen upper extremities. A custom-made native radial head prosthesis was used to simulate altered shape conditions, by rotating the radial head 90 degrees. Three-dimensional spatial orientation of the ulna was recorded, during simulated active motion. A three factor ANOVA was used to compare (a) nominal and 90 degrees oriented conditions, (b) throughout the flexion arc (c) in three forearm positions (P < 0.05). Post-hoc Tukey tests were done to assess significance. RESULTS: No significant effect of altering radial head shape was found on total ulnohumeral laxity and angulation during gravity valgus stress. We did find a significant effect on total ulnar axial rotation and rotation during gravity valgus stress. CONCLUSION: The outer shape of the radial head seems to change rotation of the ulna during flexion-extension in an otherwise intact elbow. RELEVANCE: The shape of the radial head effects intact elbow kinematics. Clinical importance of this finding is clear. If a sub-optimally placed radial head prosthesis were to be used in an otherwise intact elbow, the elbow could be at risk for early ulnohumeral arthritis.

Biomechanical Phenomena↗

PubMed2004

Contrast invariance of functional maps in cat primary visual cortex.

Neurons in cat primary visual cortex (V1) are clustered according to their preference for stimulus position, orientation, spatial frequency, and eye of presentation, thereby giving rise to functional maps. It is not known, however, whether a similar arrangement is present for stimulus contrast. Neurons in cat V1 vary considerably in their contrast responses, and might be clustered in a systematic fashion in this respect. Additionally, stimulus contrast might affect other functional maps. For example, there has been debate over whether the contrast threshold of neurons in cytochrome oxidase blobs is lower than elsewhere. Here we have imaged intrinsic signals to measure orientation maps in cat V1 at a range of contrast levels. We determined, on a pixel-by-pixel basis, contrast-response functions and orientation tuning curves. The fit parameters describing contrast responses were more or less uniform: We found no regions where neurons have lower contrast threshold than elsewhere. If such regions do exist, their functional maps must be substantially weaker than maps of orientation preference. Moreover, we found that contrast has no impact on maps of orientation preference: The orientation selectivity of each pixel is invariant with stimulus contrast. The contrast invariance that we demonstrate at the level of maps is well known at the level of single neurons. It suggests that neurons contributing to a pixel response generally have similar orientation preferences or similar contrast responses. The latter explanation is likely to hold in pinwheel centers, where preferred orientation of nearby neurons can differ markedly. In summary, our data suggest that contrast is represented uniformly over the surface of cat V1, and changes in contrast do not affect maps of orientation preference.

Animals↗

PubMed1997

The effects of coarseness of quantisation, exposure duration, and selective spatial attention on the perception of spatially quantised ('blocked') visual images.

The two objectives of the present article are (a) to present a brief overview of the effects of systematic variation of the spatial-scale value of quantisation and stimulus duration on the identification of original images that have been degraded by Harmon-Julesz type of image pixelisation by 'blocking' and (b) to report the results of two experiments where the effects of selective spatial precuing by local and global peripheral precues on the identification of quantised target stimuli have been studied. Both the overview and the new results reported here demonstrate some counter-intuitive effects: (1) abrupt decrease in identification efficiency with only a minor change in the coarseness of quantisation over a critical value of pixels per stimulus; (2) a cost for valid attentional precuing with coarse-quantised images. If physical precues (exposed with stimulus onset asynchrony of 120 ms) were employed in order to orient spatial attention to perceive original or fine-quantised stimuli, then attentional facilitation was found. However, if the precued stimuli were coarse quantised then the facilitative effect crossed over to a detrimental effect of attention. These effects are discussed in the context of the microgenetic approach that presupposes the existence of a perceptual-attentional processing routine that operates according to the coarse-to-fine time-course rule of selective attentional activation of stimulus representations at various spatial scales.

Adult↗

PubMed2006

Touch down: the effect of artificial touch cues on orientation in microgravity.

Orienting oneself in space is not an easy task. On Earth, we combine visual, vestibular and pressure cues into a coherent concept of up and down. Since there are no cues from gravity in space, astronauts have to adjust the way they determine up from down, with the possible risk of space motion sickness. In three tasks performed by one astronaut in the International Space Station (ISS), we examined the effect of artificial touch cues presented to the torso. The role of "natural" touch cues on spatial orientation in microgravity, such as pressure presented to the sole of the feet, has already been shown, but it is not trivial whether the brain can also integrate artificial orientation information that has no real life equivalent. We find that artificial touch information in the form of a localised vibration on the torso that indicates down can make orienting in microgravity faster, better and easier. The importance of the artificial touch information seems to increase over the initial 7 days of staying in microgravity while the weight of visual information decreases over the same period. The results underline the capacity of the brain to adapt to unusual environments and to use and integrate artificial cues. Besides astronauts, pilots, divers and people with a vestibular dysfunction may benefit from this technology.

Cues↗