EEG of quiet sleep in preterm infants is characterized by periodicity since large amplitude waves (bursts) alternate with attenuated low voltage activity (flats). The EEG power spectrum of bursts and flats was studied at 33, 34, 35 and 37 weeks gestational age in the same infant. Over this period of four weeks bursts showed a moderate increase in power of most frequencies with the highest increase (2.3×) in delta2 frequency band (1.5—3.5 Hz). At the same time flats displayed most dramatic changes with the highest increase (45×) in the theta1 frequency band (3.5—7.5 Hz) and with 20 to 40 fold increase in power of the integrated EEG (1.5—25 Hz frequency range). The findings were also seen in an additional 5 preterm infants studied at 2 to 4 week intervals. These striking differences in maturational changes in power-spectrum of burst and flat periods support the notion of two different sources for burst-flat periodicity: bursts originating primarily from subcortical sources and flats reflecting cortical activity.
Sleep - preterm infants - power spectra
