Integrative Cortical Functions in the Immature Brain – Investigations in Human Newborns using EEG

The perinatal period in human beings is characterized by rapid developmental changes of the CNS. Results from animal experiments indicate that spontaneous activity may be of essential importance for this development. Insights into the functional organization can be provided by EEG, but up to now only limited information is available. We hypothesize that highly organized functional patterns are generated in newborn brains in spite of their immaturity. We investigated healthy full-term newborns by multichannel EEG during quiet sleep. Part of the EEG is characterized by the recurrent appearance of high voltage periods (burst) and low voltage periods (interburst). Pattern-related analysis of this EEG was performed by calculating instantaneous spectral power, adaptive inter- and intrahemispheric coherence and the coupling between different frequency bands by bicoherence analysis. Burst periods reappeared during discontinuous EEG with a dominant frequency of about 0.1Hz. During bursts mean spectral power reached a maximum within frequency bands >2.8–14.8Hz during the first part of this period. Spectral power within the other frequency bands and during interburst periods was distributed equally. The highest coherence level was observed during burst periods in comparison to interburst periods. Maximal coherence was reached at different moments during bursts – late in the low frequency bands (0.5–1.5Hz; about 3s after the burst started) and earlier in higher frequency bands (>2Hz; about 2s). The interhemispheric coherence was highest in all frequency bands over the frontal region as compared to the central region during bursts. Mainly in frontal regions phase coupling between high and low frequency components could be described with a temporal dynamic of about 0.1Hz. It can be shown that during the early period of neurodevelopment, characteristic changes of electric potential occur, functional coupling between hemispheres exists and that the EEG expresses highly organized topographic and temporal patterns. Thus, using pattern-related investigations with high temporal resolution the newborn EEG provides evidence of early integrative cortical functions.