D U R I N G S T U D I E S of the effects of angular acceleration and centrifugal force in flight, Graybiel, Clark and McCorquodale observed two illusory phenomena which they termed the "oculogyral" and the "oculogravic" illusion. 3-5'1~'~3'~4 They attributed the oculogyral illusion to angular acceleration. This change in velocity of rotation produces an adequate stimulus to the semicircular can...

I N THE COURSE of a recent study undertaken for the Naval Training Device Center, an effort has been directed toward developing concepts of probable mechanisms for maintenance of body posture under conditions of zero gravity. Body posture is maintained by the action of the eyes and by sensory receptors which are stimulated by mechanical forces, i.e., those of the vestibular labyrinth, the neuro...

The effect of a linear harmonic vibration on heat propagation is investigated in near-critical SF6 under weightlessness conditions in space. Heat was issued from a pointlike source (thermistor), a situation representative of an industrial use of pressurized supercritical fluid storage. Two kinds of vibrations were used, large amplitude (64 mm) at 0.2 Hz and low amplitude (0.8 mm) at 1.6 Hz, wit...

The role of gravity in spatial coordinate assignment and the mental representation of space were studied in three experiments, varying different perceptual cues systematically: the retinal, the visual background, the vestibular, and proprioceptive information. Verbal descriptions of visually presented arrays were required under different head positions (straight/tilt) and under different gravit...

A weightless neural state machine acting as an exploratory automaton changes its position in a simulated toy world by its own actions. A popular question is asked: how might the automaton ‘become conscious of’ the effect of its own actions? Here we develop previously defined iconic learning in such weightless machines so that this knowledge can be achieved. Weightlessness, iconic learning are e...

Postural stress tests are useful in the assessment of cardiovascular reflex response of normal subjects who may be involved in specialised occupations such as flying; in order to study the effects of physiological stresses such as heat stress, hypoxia, simulation of weightlessness; physiological evaluation of cosmonaut candidates, in patients who may have autonomic neuropathy. Most commonly qui...

Although weightlessness is known to affect living cells, the manner by which this occurs is unknown. Some reaction-diffusion processes have been theoretically predicted as being gravity-dependent. Microtubules, a major constituent of the cellular cytoskeleton, self-organize in vitro by way of reaction-diffusion processes. To investigate how self-organization depends on gravity, microtubules wer...

Physical inactivity induced by head-down bed rest (HDBR) affects body composition (BC). Leptin is involved in BC regulation by acting on fuel homeostasis. We investigated whether leptin and counterregulatory hormone levels are affected by a 7-day HDBR. Fasting blood was sampled daily (0700) in males (n = 8) and on alternating days in females (n = 8) for measurements of leptin, insulin, norepine...

High-protein and acidogenic diets induce hypercalciuria. Foods or supplements with excess sulfur-containing amino acids increase endogenous sulfuric acid production and therefore have the potential to increase calcium excretion and alter bone metabolism. In this study, effects of an amino acid/carbohydrate supplement on bone resorption were examined during bed rest. Thirteen subjects were divid...