Amplitude spectral analysis of maturational changes of delta waves in preterm infants

The aim of this study is to clarify the usefulness of amplitude spectral analysis for an evaluation of maturational changes of delta activities in preterm infants. We chose each ten healthy infants without complications who were 29–30, 31–32, and 33–34 weeks of post-conceptional age (PCA) at electroencephalogram (EEG) recordings. Fast Fourier transform algorithm was applied for amplitude spectral analysis. The analyzed data were divided into four frequency bands; D1 0.53–1, D2 1–2, D3 2–3, and D4 3–4 Hz. The average amplitude of six segments with high voltage slow waves was calculated in each frequency band. A significant reduction of the amplitude along with PCA was present in all leads in D1 band. On the other hand, a significant negative correlation with PCA was observed only in the occipital leads in D2, D3 or D4 bands. In conclusion, maturational EEG changes assessed by amplitude spectral analysis were prominent in the occipital areas, and in the frequency less than 1 Hz.