The effect of parabolic flight on perceived physical, motivational and psychological state in men and women: correlation with neuroendocrine stress parameters and electrocortical activity.

Previous findings of decreased mental and perceptual motor performance during parabolic flights have been attributed mainly to the primary effects of weightlessness rather than the accompanying effects of stress and altered mood. Although recent studies have alluded to the possible negative effects of stress on performance, there has been no attempt to investigate this during parabolic flights. Over a period of 3 years, 27 human participants (male n = 18, mean age +/- SD 34.67 +/- 7.59 years; female n = 9, 36.22 +/- 9.92 years) were recruited with the aim to evaluate if, and to what extent, parabolic flights are accompanied by changes in mood. Furthermore, the relationships between mood and physiological markers of stress and arousal, namely circulating stress hormones (ACTH, cortisol, epinephrine, norepinephrine, prolactin and brain activity (EEG)) were investigated. A strong and significant correlation was found between circulating stress hormone concentrations and perceived physical state, motivational state (MOT) and psychological strain (PSYCHO), whereas no interaction between mood and EEG or EEG and stress hormone concentrations was observed. Therefore, two different stress responses appear to be present during parabolic flight. The first seems to be characterised by general cortical arousal, whereas the second seems to evolve from the adrenomedullary system. It is likely that both these mechanisms have different effects on mental and perceptual motor performance, which require further investigation and should to be taken into account when interpreting previous weightlessness research.

Motion and space sickness: intestinal and autonomic correlates.

The purpose of this paper is to provide an overview of autonomic nervous system and gastrointestinal changes that occur during motion sickness. It is important to consider that motion sickness is a syndrome that can vary between individuals and within individuals and between and within motion sickness-inducing stimuli. Vomiting should be considered a discrete event of the motion sickness syndrome. Given so much variability in motion sickness symptoms, it should be expected that the physiological response to motion sickness will vary as well. This appears to be the case with the autonomic nervous system and gastrointestinal changes during motion sickness. Although much research remains to be done, it appears undeniable that the physiological expression of motion sickness is mediated by the autonomic nervous system, and when nausea is a predominant symptom, the stomach in general shuts down in a response characterized by decreased normal gastric myoelectrical activity and delayed gastric emptying.

Cognitive-behavioral management of motion sickness.

This monograph is intended to provide health professionals with information on a cognitive-behavioral technique which was developed to teach individuals who are prone to motion sickness to better cope with motion environments. It includes an overview of motion sickness, describing the signs and symptoms, etiology and incidence of this malady. Prevention and treatment are then reviewed, including both pharmacological and non-pharmacological therapies. The historical background on the cognitive-behavioral technique is then discussed. This is followed by a review of supporting experimental work, and an account of how such counselling should be carried out. Finally, a number of current military desensitization programs are compared and contrasted with cognitive-behavioral therapy.

Biological and cognitive determination of the gravitational reference frame.

It is argued that space sickness is not so much a physiological problem, but a psychological one, having its roots in the perception of the environment, and its associated cognitive processing. This cognitive processing is argued to be that of field dependence and field independence, for which exist psychobiological and cognitive assessment tests. Since there is an obvious economic advantage in the use of cognite testing, it is recommended that this could be used as an initial screening when selecting for astronauts.

Nausogenic properties of various dynamic and static force environments.

Motion sickness can occur when an accelerating force acting on the human body repeatedly changes amplitude and direction or both. It also can occur without any motion after transfer into a constant force field significantly different from Earth-gravity. Dynamic and static causes of motion sickness can be distinguished accordingly. Space sickness, too, has dynamic as well as static aspects. Dynamic space sickness might depend on increased bilateral differential sensitivity of the peripheral and central vestibular apparatus, whereas static space sickness may be caused by erroneous compensation of bilaterial asymmetries of the otolith-system in the microgravity environment. Experiments in airplanes, cars and on a vestibular sled have shown that the susceptibility to motion sickness is highest for changes of acceleration in the negative X-axis (as compared to the other axes) of the body. During reciprocating linear accelerations on the vestibular sled, standstill periods of movement and the direction of movement cannot correctly be indicated, because the peripheral vestibular apparatus lacks true motion detectors.

Psychophysiological aspects of increasing resistance to space motion sickness.

One of the actual and difficulty solved problems of the adaptation period to microgravitation is space motion sickness (MS) that has the negative influence on well-being and performance of crewmembers in the initial and highly crucial phase of the orbital flight. Among the prophylactic measures for decrease of the unfavourable influence of space MS the preflight training is of great importance, and its role in perspective undoubtedly will grow in connection with increase of the number of crewmembers. During the last years several authors received experimental materials evidenced that as a base of more effective increase of resistance to space MS there may be used adequate modelling of the main physiological effects of the adaptation period to microgravitation. In the most investigations the main attention is paid to modelling of "conflicting" vestibular-visual (VV) impacts. In other hand, in connection with the contradictory materials about the role of hemodynamic component in the development of space MS this effect of microgravitation conditions, as a rule, is not modelled in the methods of resistance enhancement to space MS. Hence in this work there was put a task to investigate the efficiency of application of different combination of VV-impacts and creation of redistribution of liquid medium of an organism in the cranial direction for increase of man resistance to space MS. For resolving this task there was used the specially developed stand, made in two modifications. This stand provided redistribution of liquid medium of an organism in the cranial direction by putting the investigated individual into the antiorthostatic position (AOP). During the rotation around the vertical axis individual was placed in such supine position on the turn table that labyrinth of the inner ear should be displaced by 8-10 centimeters from the axis of rotation to the head edge of the turn table. This increased the adequacy of vestibular apparatus irritation by gravitation and inertia forces with regard to microgravitation conditions.