Spatially Oriented Research Articles

Staying Oriented While Driving

Do elderly drivers have more trouble finding their way and staying spatially oriented than younger drivers do? If spatial orientation is more difficult for elderly drivers it could distract attention from vehicle control resulting in a higher accident rate for elderly drivers. Moreover, it could become less desirable for older drivers to explore unfamiliar surroundings and as such diminish their action radius. In order to test our hypothesis that elderly drivers have more problems with wayfinding and spatial orientation drivers in two age groups were asked to perform a wayfinding task in an unfamiliar environment. Errors in orientation were measured and compared between age-groups. Results on this driving and wayfinding task support the original hypothesis that acquiring and maintaining spatial orientation is significantly more problematic for elderly than younger drivers, hence could be a distracting factor for vehicle control.

Control of spatial orientation of the angular vestibulo-ocular reflex by the nodulus and uvula of the vestibulocerebellum.

Eye velocity produced by the angular vestibulo-ocular reflex (aVOR) tends to align with the summed vector of gravity and other linear accelerations [gravito-inertial acceleration (GIA)]. Defined as "spatial orientation of the aVOR," we propose that it is controlled by the nodulus and uvula of the vestibulocerebellum. Here, electrical stimulation, injections of the GABAA agonist, muscimol, and single-cell recordings were utilized to investigate this spatial orientation. Stimulation, injection, and recording sites in the nodulus were determined in vivo by MRI and verified in histological sections. MRI proved to be a sensitive, reliable way to localize electrode placements. Electrical stimulation at sites in the nodulus and sublobule d of the uvula produced nystagmus whose slow-phase eye-velocity vectors were either head centric or spatially invariant. When head centric, the eye velocity vector remained within +/- 45 degrees of the vector obtained with the animal upright, regardless of head position with respect to gravity. When spatially oriented, the vector remained relatively constant in space in one on-side position, with respect to the vector determined with the animal upright. A majority of induced movements from the nodulus were spatially oriented. Spatially oriented movements were generally followed by after-nystagmus, which had the characteristics of optokinetic after-nystagmus (OKAN), including orientation to the GIA. After muscimol injections, horizontal-to-vertical cross-coupling was lost or reduced during OKAN in tilted positions. This supports the hypothesis that the nodulus mediates yaw-to-vertical or roll cross-coupling. The injections also shortened the yaw-axis time constant and produced contralateral horizontal spontaneous nystagmus, whose velocity varied as a function of head position with regard to gravity. Nodulus units were tested with static head tilt, sinusoidal oscillation around a spatial horizontal axis with the head in different orientations relative to the pitching plane, and off-vertical axis rotation (OVAR). The direction of the response vectors of the otolith-recipient units in the nodulus, determined from static and/or dynamic head tilts, were confirmed by OVAR. These vector directions lay close to the planes of the vertical canals in 7/10 units; many units also had convergent input from the vertical canals. It is postulated that the orientation properties of the aVOR result from a transfer of otolith input regarding head tilt along canal planes to canal-related zones of the nodulus. In turn, Purkinje cells in these zones project to vestibular nuclei neurons to control eye velocity around axes normal to these same canal planes.

Vibration-induced postural posteffects.

It generally is known that vibration of various muscles in free-standing subjects evokes a spatially oriented postural response. Furthermore, it recently has been shown that when a vibratory stimulus is terminated, a powerful involuntary contraction of the previously vibrated muscle often occurs that, under the isotonic condition, is accompanied by movement of a limb. The aim of this study was to explore effects of a low-amplitude mechanical vibration, applied in a seated position, on the standing posture. The 30-s vibration was applied bilaterally at the ankle level to anterior or posterior tendons and at the cervical level in front or back of the neck, at one site only at a time. Center of pressure trajectories were monitored during quiet stance for </=19 min after the offset of vibration, and these measurements were compared with a previbration control trial. The results clearly indicate that vibration produced in all subjects strong, long-lasting dynamical modification of posture mainly in the anterior-posterior direction. Spatial orientation of the induced postvibratory shift in posture was dependent on the vibration side. We conclude that sustained Ia sensory inflow, evoked by vibration, has a powerful after-effect on the motor system at the postural level.

Effect of molecular orientation on electron impact ionization and fragmentation

Relative ionization cross sections have been determined for the production of the molecular ion CH3Cl+ and the fragmentation product CH+3 from the 200 eV electron impact ionization of spatially oriented CH3Cl molecules in a cross beam experiment. The ionization cross section for CH3Cl+ formation is higher at the positive end, or CH3 end, of the molecule while the cross section for formation of the CH+3 fragmentation product is independent of spatial orientation, within experimental uncertainty.

Optical spectra of spatially oriented molecules: ICl in a strong electric field

Strong electric fields can hybridize rotational states of polar molecules and thus create pendular states in which the molecules are confined to librate over a limited angular range about the field direction. In this way, substantial spatial orientation can be attained for the lowest rotational states of many linear, symmetric and asymmetric top molecules. A large fraction of a molecular ensemble can often be condensed into these low rotational states by cooling in a supersonic expansion. Pendular eigenstates differ qualitatively from those of a rotor or an oscillator and can be observed spectroscopically; this provides a means to characterize the extent of the orientation achieved. Here we present high-resolution laser-induced fluorescence spectra of ICI A 3Π1â†� X 1Σ0 measured as a function of the electric field strength up to 36 kV cm–1. These spectra are compared with calculated transition frequencies and probabilities between pendulum/pinwheel states. The field-induced mixing of J states changes the transition probabilities markedly and enriches the spectra with many transitions that would be forbidden in the absence of the field. The transition probabilities fluctuate as the angular lobes of the two pendular wavefunctions involved come in and out of phase when the field strength is varied. The observed fluctuations are particularly pronounced in the present case because the dipole moment changes sign between the two electronic states.

Ultrasonic apparatus for positioning a robot hand

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Evidence for caudate nucleus involvement in an egocentric spatial task: Return from passive transport

Potegal (1972) proposed that the caudate nucleus was involved in processing sensory (especially vestibular) cues for egocentric spatial orientation. The purpose of these experiments was to determine the effect of caudate nucleus lesions on a return from passive transport (RPT) task, which has been shown to depend on vestibular input (Miller, Barnett, & Potegal, Note 1). In the first experiment, 18 male rats were trained on RPT. Six then received bilateral posterior caudate lesions, 6 received bilateral control lesions in the dorsal hippocampus, and 6 served as sham-operated controls. Postsurgical retraining revealed deficits in RPT for the caudate group, relative to hippocampal and sham groups. To test the specificity of the caudate lesion effect, a second experiment examined the effect of caudate and hippocampal lesions on an exteroceptive-cue-based spatial task, olfactory trail finding (OTF). Neither posterior caudate lesions nor dorsal hippocampal lesions produced deficits in OTF. These results suggest that the role of the posterior caudate in spatially oriented behavior is restricted to egocentric orientation based on vestibular cues. Since the caudate lesions had no effect on air-righting behavior, any vestibulostriatal contribution to RPT must be separate from the regulation of righting reflexes. This contribution may be mediated via the posterior portion of the caudate. Failure to find an effect of hippocampal lesions on RPT supports the suggestion that hippocampal involvement in spatial behavior may be restricted to memory and mapping of exteroceptive cues (O’Keefe & Nadel, 1978).

THE CROSS‐SECTIONAL ECHOCARDIOGRAM IN CLINICAL CARDIOLOGY: APPLICATIONS AND RELATIONSHIP TO THE M‐MODE TECHNIQUE.

SUMMARYUntil recently M‐mode echocardiography has been the standard in clinical practice. Although the M‐mode systems provide rapidly acquired, high resolution data concerning regional cardiac interface position and motion, the limited area encompassed by the narrow M‐mode beam and failure to provide spatial orientation may be a significant limitation in selected clinical areas.Cross‐sectional echocardiography expands the area of the heart which is available for study and displays the acoustic images in a dynamic spatially oriented format allowing the moving cross‐sectional anatomy of the heart to be visualized. This variation in method of display provides more extensive information concerning valvular heart disease by permitting analysis of the morphology and motion patterns of the cardiac valves, direct visualization of valvular orifices, and appreciation of valvular movement in relationship to surrounding cardiac chambers. In patients with ischemic heart disease the cross‐sectional systems increase the area of the ventricle which is available for ultrasonic study by adding the cardiac apex and the medial and lateral walls of the ventricle to the recorded data. In addition the systems permit localized distortion in left ventricular shape and function to be evaluated. Finally, in congenital heart disease the cross‐sectional systems permit the orientation of the great vessels and cardiac chambers to be determined. In this report we have presented examples of the applications of cross‐sectional echocardiography in each of these areas in the hope that the reader can gain from these isolated examples an overall appreciation of the potential of this type of instrumentation and its relationship to be more conventional M‐mode display.

Anatomy of the facial nerve (spatial orientation of fibers in the temporal bone).

AbstractThe spatial relations of the peripheral branches of the facial nerve within the temporal bone were studied. Five groups of experiments were performed, using 48 adult cats. The topographical anatomy of the horizontal segment was demonstrated by evoked EMG in two cats with injuries to the lateral aspect of the horizontal segment of the facial nerve. The upper face was more severely injured than the lower. The cross sectional spatial anatomy of the horizontal segment of the facial nerve was mapped out in seven cats by histopathologically correlating the lesion site with the peripheral distribution. Gross dissections in 14 cats demonstrated the cross sectional spatial relationships of the peripheral fibers at the stylomastoid foramen and distal portion of the vertical segment. Temporal bone sections in five cats added further to the orientation of the facial nerve.The following conclusions were drawn from this study: The facial nerve was spatially oriented in its tympanomastoid segment; the branches to the ear and chorda tympani nerve were lateral (toward the mastoid cortex); the forehead and eye lateroanterior (toward the middle ear); the lower lip anteromedial (toward the floor of the middle ear); the upper midface posterior (toward the horizontal canal), and the lower midface just anterior to the upper midface. The peripheral fibers rotated as they coursed from the stylomastoid foramen toward the face; the lower branches twisted under and medial to the branch just above them. The lower face branches twisted from an anteromedial position in the horizontal segment to a posteromedial position at the stylomastoid foramen. The upper midface branches changed position from a posterolateral position at the horizontal segment to anteromedial at the stylomastoid foramen. The branch to the stapedial muscle separated from the horizontal segment of the facial nerve from a posteromedial position. The branch to the stylohyoid muscle and posterior bolly of the digastric muscle separated from the facial nerve just beyond the stylomastoid foramen from a posteromedial position. A review of the literature suggested a close resemblance between the anatomy of the facial nerve in cat and man; therefore, the detailed anatomy of the cross section of the cat's facial nerve within the temporal bone should have direct clinical application.