rats in all frequency ranges and both electrode sites (FCTX, PCTX) except for beta frequencies in the frontal cortex. It has long been known that EEG recordings from children are dominated by high amplitude slower rhythms that diminish in amplitude and increase in frequency over the course of adolescence (see [108-112]) and that deviations from normal patterns have been associated with abnormal or delayed brain maturation [113]. It has also been suggested that gray matter loss or synaptic pruning may underlie these developmental changes seen in EEG amplitude over adolescent development [114]. However, it is still less clear how such changes in EEG spectral amplitude are related to cognitive changes also occurring during this time period. EEG spectral power reflects changes in both the size and strength of the neuronal assemblies engaged in stimulus processing and also to what extent the neural ensembles are in phase-synchronization [21, 115]. Our data suggest that both the size of the neural assemblies and their degree of phase locking are changed over adolescent development.
