QUADRATIC PHASE COUPLING AS A QUANTITATIVE MEASURE FOR THE DEVELOPINGHIPPOCAMPAL-FORMATION

This paper presents the bispectral analysis of the ontogeny of the hip pocampal EEG recorded from the dentate gyrus and CA1, the primary site s that generate theta (theta) rhythm. The hippocampal EEG was collecte d during the vigi lance state of rapid eye movement (REM) sleep of fre ely moving rats at 15, 30 and 90 days of age. In previous studies we d emonstrated through bispectral analysis that significant quadratic pha se coupling (QPC) of the EEG exists in the hippocampal formation of CA 1 and the dentate gyrus during REM sleep, primarily in the theta (4-11 Hz) frequency range. In the present study we have examined whether QP C can be used as an effective measure of development, i.e., maturation of the hippocampal subfields CAL and the dentate gyrus. We found that as animals mature from the age of 15 to 90 days, the occurrence of no nlinear QPC activities moves from (6.25 Hz, 6 Hz) to (7 Hz, 7 Hz) at C A1 and (6 Hz, 6 Hz) to (7.5 Hz, 7.5 Hz) at the dentate gyrus, respecti vely. The results indicate that bispectral analysis provides an additi onal and important description of the frequency characteristics of the hippocampal EEG and that the QPC measure is also a useful index to qu antify the shift in the hippocampal a frequency as animals mature. (C) 1998 Biomedical Engineering Society.