胎児行動における中枢神経系制御機構の発達過程に関する総合的解析 (<シンポジウム>胎児の行動 (fetal behavior) : その基礎と臨床)

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The development of central nervous system (CNS) is the latest among the various fetal organs and is on the way to mature even at birth. Because behavior is the phenotype of the CNS function, the behavioral pattern significantly changes with the developmental stage of CNS throughout the whole fetal period. The purpose of this study is to clarify the developmental sequence of fetal behavior and to discuss the functional development of the fetal CNS. For the first step of this study, thirty-one normal pregnant women, between 20 and 41 weeks of gestation, were examined for 60 minutes by using four ultrasonographic machines, which were employed simultaneously for observing four parts of each fetus : head, trunk, upper and lower extremities. All fetal movements were categorized according to the moving parts of the body and the pecuriarities of movement. Trunk movements include six types i.e. flexion, strech, rolling, startle, jumping (stepping), and writhing. The peak incidences of flexion and strech were in 28〜31 weeks of gestation. The incidence of rolling movements was high in 24〜27 weeks, thereafter lowered gradually with gestational age, and then showed the significant increase in 40〜41 weeks. The incidences of startle and jumping movements were high before 28 weeks, and then decreased significantly. Writhing movements were often observed after 28 weeks. The other movements showed the respective patterns of the changes in the incidence. Secondly, animal experiments were performed to obtain the basic data on fetal behavior which could not be given by the ultrasonographic observation of human fetuses. Fetal goats were incubated under the physiological condition in artifitial amniotic fluid by using extracorporeal membrane oxygenation (ECMO) system. EEG, EOG, intratracheal pressure, EMG of nucal and thigh muscle were monitored continuously. Four categories of behavioral states were defined on the basis of the findings of these monitoring and the fetal movements observed with naked eyes. The effects of PGE_2 and PGD_2, which are known as regulators of sleep-wakefulness cycle, on behavioral states defined above were investigated to clarify the meanings of these behavioral states. As a result of these experiments, it was suggested that four categories of behavioral states in extra-uterine fetal goats were deep Non-REM sleep, shallow Non-REM sleep, REM sleep and wakefulness. Finally, a study on the development of behavioral states in human fetus was conducted. Materials were the same pregnant women mentioned above. By observation of fetal rapid eye movements (REM) three periods (i.e REM period, Non-REM period, and equivocal period) were defined. The REM period was significantly longer on 24〜27 weeks than before. It was not until 24 weeks that the significant difference in the incidence of startle was seen between the REM and the Non-REM period. These findings suggest that REM sleep begins on 24〜27 weeks of gestation. The highest correlation between REMs and breathing movements was found in 28〜31 weeks of gestation. Moreover, the REM period with high density of REMs increased with gestational age. REM sleep is thought to develop through the latter half of pergnancy. Non-REM period dose not mean directly Non-REM sleep. It is important for investigating the development of Non-REM sleep to find the characteristic phenomena happened not in the REM period but in the Non-REM period Mouthing is known as the characteristic movement observed in Non-REM sleep in the neonate. After 32 weeks of gestation, the incidence of mouthing in the Non-REM period became high-Moreover, the incidence of trunk movements and limb movements significantly decreased in the Non-REM period after 36 weeks. The development of Non-REM sleep is thought to begin about 32 weeks and become overt after 36 weeks of gestdtion. The incidence of rolling movements in the REM priod was higher than the other periods after 37 weeks of gestation. Rolling movements in the REM pe
社団法人日本産科婦人科学会の論文
1991-08-01

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