Ontogenetic changes in heartbeat fluctuation and nonlinear interactions between neural oscillators

点击翻译按钮获取中文摘要

In this research project, we have tried to elucidate the ontogenetic changes of heart beat period fluctuations in chick embryos. The results obtained from this study are summarized as follows :(1) Electrocardiogram (ECG) colud be recorded from chick embryos at about the 10th day of incubation (DI). During this period, there was little fluctuation in heartbeat periods. However, the heartbeat fluctuation, especially the low-frequency components of it, became greater as the DI increased.(2) The spectrum analysis of heartbeat fluctuation disclosed that the power spectral density of the heartbeat periods was almost flat like a white noise in the early period of incubation. However, the spectral density became inversely proportional to the frequency as embryos grew up, and finally showed the characteristics of 1/f fluctuation at the 17th or 18th DI.(3) A spectral component representing the respiratory modulation of the heartbeat was first observed at about 10th DI,and the component became greater during development of the chick embryos.(4) A model study using mutually interacting nonlinear BVP oscillators showed that a bunch of oscillators functions as a single "limit-cycle oscillator" when the coupling strength between them is strong.All the above results suggested that the autonomic nervous control of the heart may fully developed by about the 17ty DI,and that the spectral changes of heartbeat fluctuation may reflect the ontogenetic process of the autonomic nerve innervation of the heart.