BACKGROUND: Organisms have developed endogenous mechanisms for keeping track of time which allow them to adjust to environmental changes. Entrainment of endogenous rhythms to the day-night cycle is of elementary importance for the regulation of physiological processes. How environmental changes influence the manifestation of circadian rhythms during intrauterine and extrauterine growth depend on complex networking of molecular, physiological and sensory mechanisms. This work reports on development of circadian rhythms in the infant, with particular emphasis on the roles of times cues to which the infant is exposed. SUBJECTS AND METHODS: Activity data of 12 families were continuously recorded during the first 4 months after birth using non-invasive actigraphs. Recordings of parental activity started at the 3rd trimester of pregnancy. Time series analysis was used to investigate the periodic structure of the data. In addition, we review the literature on the ontogenesis of circadian rhythms in humans. RESULTS: During the 3rd trimester, daily variation of physiological functions in the fetus showed a high degree of correspondence with maternal circadian rhythms. Early behaviour of most infants was highly variable between individuals but could be assigned to different entrainment patterns. Good correspondence of mother-infant activity patterns during the early postnatal period, when the infant was not yet entrained to the day-night-cycle, was correlated with the rapid development of an entrained daily pattern in the infant a few weeks later. CONCLUSION: Understanding the emergence of periodic structures at physiological and behavioural level during human ontogenesis will be an asset in the successful intervention and treatment during neonatal care.

Child Development↗

PubMedDate not supplied

[West syndrome: a chronobiological approach].

INTRODUCTION AND OBJECTIVES: Chronobiology is the discipline involving the study of the time structure of living creatures. Since it has been shown that there is non-chaotic recurrence, at precise intervals of time, of different functions from unicellular level to complex human systems, rhythmometric evaluation of key activities such as the activity-rest and sleeping-waking cycles appear to be useful non-invasive instruments for study of time structure in patients with episodic illness of the central nervous system (CNS) such as the epilepsies, in this case a serious variety of this disorder in childhood: West's syndrome. PATIENTS AND METHODS: We studied the activity-rest and sleep-waking cycles of two patients with West's syndrome and also their parents, using actometres (ZAK, made in Germany). At the same time the parents kept diaries (which they had previously been taught to do) at intervals of 20 minutes. They recorded the time of meals, administration of medicines, occurrence of seizures and data regarding the sleep of the patients. On subsequent analysis actograms were obtained. These are quantitative recordings of continuous motor activity. RESULTS: A rhythm of a type lasting more than 24 hours was observed during the activity-rest and sleep-waking cycles in both patients, with predominance of seizures during the early hours of the day. There was also a high degree of synchronization in the mother-child interactions. CONCLUSION: The presence of a rhythm of more than 24 hours in activity-rest and sleeping-waking shows the marked immaturity of the CNS in these patients, directly related to the severity of this type of epilepsy.

Activity Cycles↗