Regional differences in spectral EEG measures between healthy term and preterm infants.

State-specific spectral electroencephalographic (EEG) values were compared among 14 bipolar channel derivations between two healthy neonatal cohorts. Fifty-five healthy preterm neonates of < or = 32 weeks gestational age at birth were studied with 24-channel recordings over 3 hours at term conceptional age. These were compared with studies of 45 healthy term neonates. Five spectral measures for each channel (i.e., total spectral EEG, delta, theta, alpha, and beta frequency ranges) were calculated for each minute, which was identified as active or quiet sleep, based on visual analysis. Using multivariate analysis of variance, differences at each channel were assessed between neonatal cohorts for both states and cohorts; higher total EEG spectral values were noted during active sleep; whereas higher delta and theta spectral values were noted during quiet sleep. The term cohort had higher values for spectral theta, alpha, and beta power spectra in multiple channels, most significantly in the left central (i.e., C3O1) and sagittal regions (FzCz, CzPz) during both states (P < .0001, adj r2 > or = .2). Both interhemispheric and intrahemispheric differences in spectral values were present. For a healthy preterm cohort, lower spectral energies are expressed during sleep in specific head regions. Physiologic asymmetries exist in the newborn brain which are unique for the preterm infant, emphasizing functional alterations in brain development. How these asymmetries are altered by prenatal or postnatal stress or disease states needs to be explored.