PubMed · 3827210
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S Noda, K Ide, H Umezaki, H Itoh, K Yamamoto. 1987. Repetitive divergence.. https://doi.org/10.1002/ana.410210123
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Persisting asymmetries in the motility and posture of preterm infants after term age is a common finding, but their diagnostic and prognostic significance has proved to be difficult to interpret. It has been claimed that if an asymmetry is of central origin, then it should be most prominently detectable in infantile reactions that persist beyond the age when they should have disappeared. We hypothesis that motor asymmetries in preterm infants without a major risk for neurological problems may stem from a high degree of active muscle power in the trunk that continues to be present after 12 weeks corrected age. In order to test this hypothesis, 34 preterm infants with a low risk for neurological complications were compared to a group of 17 fullterm infants at 18 weeks of (corrected) age for the presence or absence of motor asymmetries. None of the full-term infants showed asymmetrical motor behaviour, while within the preterm group a significant number did, in particular those who were small for gestational age. A significant relationship between motor asymmetries and a high degree of muscle power in the trunk at this age was found in the preterm group. Asymmetrical active muscle power at 18 weeks had a good predictive value for asymmetrical locomotor, hand and eye functions at 52 weeks.
Disk-shaped luminance increments were added to the intersections of a Hermann grid consisting of medium grey bars on a black background. Illusory spots, darker than the background, were perceived as flashing within the white disks with each flick of the eye. This striking phenomenon may be referred to as the scintillating grid illusion. We determined the conditions necessary for cancelling the Hermann grid illusion, as well as the luminance requirements and the size ratio between disks and bars that elicits the scintillation effect. The fact that scanning eye movements are necessary to produce the scintillation effect sets it apart from the Hermann grid illusion.
The effects of weightlessness on vestibular function have been studied since the beginning of manned spaceflight. The results of these studies have been highly variable and to some extent even contradictory, which makes it difficult to draw unambiguous conclusions. This variability is probably due to at least three factors: (1) individual differences in the adaptive process, (2) non-standardized experimental methods and conditions, (3) a lack of integrated experiments. For this reason, we have used a single integrated approach with a specially developed battery of tests. The results thus obtained for 21 cosmonauts on short- and long-term flights are reviewed here, and discussed in the light of the results obtained by others. Changes in the operation of the vestibular system and in all functions based on vestibular afferent input are commonly observed in spaceflight. These changes are characteristic for the process of adaptation and re-adaptation to altered gravity. They occur in a high proportion of persons exposed to such conditions, although there are individual differences with regard to severity, nature, time and duration of occurrence, and the dynamics of the process. Analysis of the observations in a large number of cosmonauts has permitted to distinguish three types of adaptation of the system to altered gravity. The first type of adaptation is characterized by a strong response to any stimulus during the initial adaptation period. The second type of adaptation is characterized by responses that are drastically decreased or even absent. The third type of adaptation is distinguished by the selective response of the sensory system to certain types of stimulation only. After long-term missions the process of re-adaptation usually takes a more severe course than the earlier process of adaptation to microgravity. Both adaptation and re-adaptation follow an undulating course, in which adaptation and re-adaptation are alternating. This is most conspicuous during long-term flights, and it suggests that in the initial stage of adaptation to weightlessness the vestibular input plays a dominant role, while at the end of the adaptation process the visual input prevails.