脳と発達
Online ISSN : 1884-7668
Print ISSN : 0029-0831
ISSN-L : 0029-0831
いわゆるtrace alternantからみた未熟児の脳波発達
周波数分析器による検討
岩瀬 勝彦渡辺 一功原紀 美子
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1973 年 5 巻 1 号 p. 41-47

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In preterm and full-term infants, the EEG during quiet sleep is characterized by burst of large amplitude slow waves with sometimes superimposed rapid rhythm (burst), alternating with attenuated periods of various frequencies (suppression) … so called “trace alternant”.
This tracé alternant pattern changes with conceptional age. In early conceptional ages, the “suppre ssion” period shows, in practice, no electrical activity. The difference between “burst” and “suppre ssion” becomes less distinct with increasing conceptional age. To demonstrate this difference quantit atively, the frequency analysis was serially performed by means of automatic analyser in 8 preterm infants, for each 5 second epoch of “burst” and “suppression”, The ratios of integrated values for suppression period to those for burst period increased in all frequency bands (σ1: 2-4c/s, θ: 4-8c/s, α: 8-13c/s, β1: 13-20c/s, β2 20-30c/s) with conceptional age. The same maturational change was also found in the ratios of total energy of “suppression” to “burst”. On the contrary, there was no difference in the power spectrum in burst and suppression at all conceptional ages. The gradual increase of the electrical activity in suppressed part of trace alternant, which has been substantiated quantitatively in this study, may be due to the maturation of the cerebral cortex in infants.

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