Automated identification and quantitation of four patterns of electrocortical activity in the near-term fetal lamb.

Most previous efforts to characterize electrocortical states in the unanesthetized fetal lamb have relied on descriptive measures of amplitude and frequency; those that used quantitative parameters did not draw upon data from a cohort of subjects for contiguous time segments. We have used Fourier analysis to quantitate amplitude and frequency characteristics of records of 2-3 h for a group of fetuses. Four electrocortical states, including two types of transitional activity, have been identified and quantitated. Additionally, we have developed a method that automates the assignment of data to these four electrocortical states. This has enabled us to monitor transitions among states and indicates that epochs that appear homogeneous by descriptive measures may actually encompass several patterns of electrocortical activity.