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At least 343 records · Page 19

Vestibular adaptation in man - Effects of increased acceleration during different phases of adaptation.

The purpose of this study was to investigate the course of vestibular adaptation following a temporary increase in angular acceleration (A). Eight normal subjects, who were rotated in a precision rotation device, gave periodic magnitude estimates of their perceived velocity throughout a prolonged 1 deg per sec per sec acceleration, which was briefly increased to either 2 or 3 deg per sec per sec at four points in the adaptation cycle. The data, tested with analysis of variance, showed that the size of the magnitude estimates was influenced by the magnitude and position of the altered A. The duration of subjective response was affected only by the position of the altered A.

Luster, T.↗

Comparative anatomy of the vestibular nuclear complex in submammalian vertebrates.

A synopsis of the literature on the natural history of the vestibular nuclear complex (VNC) in lower vertebrates is presented in an attempt to assess the knowledge available. The review discloses that there is considerable descriptive information that is widely dispersed in the literature. However, information about the topology, number, and cellular composition of the cell groups that compose the VNC is sketchy. Major cytological and hodological information is still needed to establish which parts of the VNC actually are homologous.

Mehler, W. R.↗

Experiment M-131 - Human vestibular function.

The purpose of the M-131 experiment is to measure responses in astronauts throughout orbital flight that reflect vestibular function and compare them with measurements made before and after flight. Three subtasks require measurement of (1) susceptibility to motion sickness, (2) thresholds of response to stimulation of the semicircular canals, and (3) space perception, viz, visual and nonvisual localization, using external spacecraft and internal morphological frames of reference. Four astronauts will be available for all measurements in Skylab 2 and 3 and two additional astronauts for only the 'static' measurements during the flights.

Miller, E. F., II↗

Scanning electron microscopy of the vestibular end organs

The vestibular end organs, after chemical fixation, were freeze dried, coated with gold and palladium, and studied in the scanning microscope. Scanning microscopy gives a good three dimensional view of the sensory areas and allows study of both gross anatomy and microstructures. Cross anatomical features of the structure of the ampullae are demonstrated. The form of the statoconia in different species of animals is shown. New aspects of the structure of the sensory hairs are revealed. The hair bundles in the central areas of the cristae and in the striola of the maculae differ structurally from the hair bundles at the periphery of the sensory regions. Furthermore, some hair bundles consisting of very short stereocilia were observed. The relationship between the cupula and the statoconial membrane to the epithelial surface is discussed.

Lindeman, H. H.↗

Fine structural changes in the lateral vestibular nucleus of aging rats

The fine structure of the lateral vestibular nucleus was investigated in Sprague-Dawley rats, that were sacrified at 4 weeks, 6-8 weeks, 6-8 months, and 18-20 months of age. In the neuronal perikaria, the following age-associated changes were seen with increasing frequency with advancing age: rodlike nuclear inclusions and nuclear membrane invaginations; cytoplasmic dense bodies with the characteristics of lipofuscin; and moderate disorganization of the granular endoplasmic reticulum. Dense bodies were also seen in glial cells. Rats 18 to 20 months old showed dendritic swellings, axonal degeneration, and an apparent increase in the number of axosomatic synaptic terminals containing flattened vesicles (presumed to be inhibitory in function).

Johnson, J. E., Jr.↗

Vestibular function in the space environment

The present work presents new results about the interdependence of optical illusory sensations and eye movements in man. To establish to what degree certain illusions previously obtained during centrifugation and parabolic flight can be explained by eye movements and by neuronal integration in the brain, real eye movements were measured as they occurred in the dark without optical fixation, during rectilinear accelerations on the ground, and during weightlessness in parabolic flight. Results provide valuable insight into normal vestibular function as well as resolution of within-the-eye and behind-the-eye contributions to the above illusions.

Von Baumgarten, R. J.↗