Bispectral analysis of EEG burst patterns from piglets during recovery from asphyxia

The aim of this study was to study phase coupling among different frequency components in EEC burst patterns observed in piglets during recovery from asphyxia and to compare them with those of the awake baseline EEG data. Phase coupling was quantitated by determining the average bicoherence index within the delta band along the main diagonal in the bifrequency plane. Multiple instances of burst patterns from each experiment were analyzed for phase coupling and compared with the corresponding baseline EEG data. The baseline EEG data did not show any significant phase coupling within the delta band of frequencies in any of the experiments. The raw averaged bicoherence indices within the delta band of bursts was higher than that of corresponding baseline in almost all instances. The authors, therefore, conclude that the delta frequency components of the EEG tend to become more phase coupled during the initial phase of recovery of the brain from an asphyxic injury.