Functional interactions within the newborn brain investigated by adaptive coherence analysis of EEG

To assess functional cortical organization in newborns during quiet sleep w e investigated instantaneous interhemispheric coherences in six healthy ful l-term subjects using linked ear reference and average reference. Trace alt ernant was the most frequent EEG pattern during quiet sleep of these newbor ns and consists of burst and interburst periods. The calculation of coheren ce was performed by means of time-variant autoregressive models on the basi s of Kalman filtering. Coherence changes simultaneously with the appearance of these burst and interburst periods. The highest level of coherence was observed during burst periods in comparison with interburst periods. The lo west level of coherence was observed just before the burst started. During burst, maximal coherence was reached at different moments - late in the low frequency band (0.5-1.5 Hz; about 3 s after the burst started) and earlier in higher frequency bands (> 2 Hz, about 2 s). Interhemispheric coherence depended on the region being investigated. A significant level of coherence could be observed over frontal, temporal and occipital regions. Our data d emonstrate significant modification of interhemispheric coherence during qu iet sleep of full-term newborns and, irrespective of the immaturity of the brain, these coherences differ significantly between cortical regions. (C) 2001 Editions scientifiques et medicales Elsevier SAS.