Assessment of electroencephalographic functional connectivity in term and preterm neonates

Objective: To study how functional connectivity of neonate EEG during sleep is assessed by different interdependence indices and to analyze its dependence on conceptional (CA), gestational (GA) and/or chronological age (CRA). Methods: EEG data from eight cortical regions were recorded during active (AS) and quiet sleep (QS) in three groups of seven neonates each: preterm (PT; GA: 33-34 weeks; CA: 39-40 weeks), junior-term (JT; GA: 38-39 weeks; CA: 39-40 weeks) and senior-term neonates (ST; GA: 38-39 weeks; CA: 44-45 weeks). EEG functional connectivity was assessed bymeans of the coherence function (its magnitude (MSC) and its imaginary part (IMC)) and a measure of phase synchronization called phase lag index (PLI). Results: Inter-hemispheric connectivity: (a) during AS in the beta band, the MSC of the ST group was greater than that of the PT group for the temporal region; (b) during QS in the delta band, both PLI and IMC of the ST group were different to those of the PT group for the frontopolar and central regions, whereas ST-JT differences were only found for PLI. Intra-hemispheric connectivity: (a) during AS in the beta band the MSC of the ST group was greater than that of the PT group for the left frontopolar-centrotemporal and right occipital-centrotemporal regions; (b) during QS in the beta band, both IMC and PLI were different for the JT group than for the PT and the ST groups for the right and left occipital-centrotemporal regions. Conclusions: EEG inter-and intra-hemispheric functional connectivity in neonates during sleep changes with the CA and CRA in delta and beta bands. Significance: The neonate's brain development during the first weeks of life can be traced from changes in the characteristics of EEG functional connectivity. (C) 2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.