This research project will utilize newly developed surgical and recording techniques to quantitatively examine the ontogeny of inhibitory/facilitatory modulation of the dentate granule cell population. The recordings will be done in chronically implanted, behaving, preweaned rats. Extracellular field potentials will be obtained in response to single- and paired- pulse stimulation of the perforant path. Bispectral analysis and non- Gaussian autoregressive modeling techniques will be used to characterize the development of the hippocampal EEG during the early postnatal period of development. These studies will shed new light on the interactions which occur between hippocampal neural systems responsible for the generation of hippocampal EEG patterns as the animal interacts with its environment during the early postnatal period of development. The results will provide new approaches to probe questions related to the maturation of neural circuits and developmental patterns of the EEG in behaving animals.