Amplitude spectral analysis of theta/alpha/beta waves in preterm infants

The aim of this study is to clarify the usefulness of amplitude spectral analysis for the evaluation of maturational changes of theta, alpha, and beta activities in preterm infants. We chose 10 healthy infants, who were born without complications other than prematurity, who were 29-30 weeks, 31-32 weeks, and 33-34 weeks of postconceptional age, respectively, at time of electroencephalogram recordings. Fast Fourier transform algorithm was applied for amplitude spectral analysis. The analyzed data were divided into five frequency bands: theta 1 4-6 Hz, theta 2 6-8 Hz, alpha 8-13 Hz, beta 1 13-20 Hz, and beta 2 20-30 Hz. The average amplitude of six segments with continuous patterns with high-voltage slow waves of preterm infants was calculated in each frequency band. A significant reduction of the amplitude along with postconceptional age was present in all leads in theta 1 and theta 2 bands. On the other hand, a significant correlation with postconceptional age was not observed in alpha, beta 1, or beta 2 bands. In conclusion, maturational electroencephalographic changes assessed by amplitude spectral analysis were prominent in theta activities and were not remarkable in alpha or beta activities.