Auto-regressive analysis of EEG reveals brain´s response to injury

The authors hypothesize that an insight into brain injury during hypoxia-asphyxia and recovery can be gained by quantifying the changes in frequency characteristics of EEG. Neonatal piglets (1-2 weeks old) are hypoxiated and asphyxiated to simulate severe birth related insult. Continuous Auto-Regressive (AR) analysis of EEG records is done to obtain three dominant frequencies corresponding to three poles in the spectrum. The results show an increase in power in all three frequency components (upto 200% of baseline) during hypoxia, the rate of increase being maximum for the highest frequency component. The power goes down to approximately zero within 40-60 secs. of asphyxia. Recovery in power occurs in a bursting fashion, most clearly elicited in the lowest frequency. This result is consistent with burst-suppression during recovery reported in the literature