PubMed · 4317547
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C B Parry. 1970. Trick movements.. https://pubmed.ncbi.nlm.nih.gov/4317547/
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"Normal" human subjects were placed in a series of 5 static orientations with respect to gravity and were asked to view an optokinetic display moving at a constant angular velocity. The axis of rotation coincided with the subject's rostro-caudal axis and produced horizontal optokinetic nystagmus and afternystagmus. Wall (1) previously reported that these optokinetic afternystagmus responses were not well characterized by parametric fits to slow component velocity. The response for nose-up, however, was larger than for nose-down. This suggested that the horizontal eye movements measured during optokinetic stimulation might include an induced linear VOR component as presented in the body of this paper. To investigate this hypothesis, another analysis of these data has been made using cumulative slow component eye position. Some subjects' responses had reversals in afternystagmus direction. These reversals were "filled in" by a zero slow component velocity. This method of analysis gives a much more consistent result across subjects and shows that, on average, responses from the nose-down horizontal (prone) orientation are greatly reduced (p < 0.05) compared to other horizontal and vertical orientations. Average responses are compared to responses predicted by a model previously used to predict successfully the responses to post-rotatory nystagmus after earth horizontal axis rotation. Ten of 11 subjects had larger responses in their supine than their prone orientation. Application of horizontal axis optokinetic afternystagmus for clinical otolith function testing, and implications for altered gravity experiments are discussed.
Increased risk of renal stone formation during space flight has been linked primarily to increased calcium excretion from bone demineralization induced by space flight. Other factors contributing to increased risk include increased urinary calcium oxalate supersaturation, while urinary citrate, magnesium and volume are all decreased. The aim of this study was to increase the predictive value of stone risk profiles for crew members during space flight by evaluating the excretion of urinary protein inhibitors of calcium crystallization so that more comprehensive stone risk profiles could relate mineral saturation to the concentrations of inhibitor proteins. Levels of urinary osteopontin (uropontin) are reported in a series of 14 astronauts studied before, during, and after space flights. During space flight, a compensatory increase in uropontin excretion was not observed. However, the uropontin excretion of a majority of astronauts was increased during the period after space flight and was maximal at 2 wk after landing. The downward shift in the molecular size of uropontin observed in samples obtained during space flight was shown to result from storage at ambient temperature during flight, rather than an effect of microgravity on uropontin synthesis.
This contribution surveys the sources and the processing of spatial information about posture, that is, about the orientation of the body and its parts with respect to the vertical (whereas 'position' designates their orientation to each other). Postural information is, to a considerable extent, gained by sense organs in the head. Hence information gained by the mobile eyes and the pitched-up labyrinths is first transformed from a retinal and otolithic into a head-fixed frame of reference, then from head- to trunk-fixed coordinates, and, finally, from a trunk-fixed to an exocentric frame of reference. To that end the position of eyes and otoliths to the head, of the head to the trunk, and of the trunk to the rest of the world must be known, deduced by efference copies or measured by proprioceptors. It is shown that the perceived relation of the visual world to the vertical is exclusively determined by sense organs in the head, whereas body posture is also directly measured by recently discovered graviceptors in the human trunk. It appears that the proprioceptors mediate perception of position, but not, or only indirectly, of posture.