The present experiments were carried out in order to characterize the changes in ECoG spectrum power occurring in old compared with young rats. In addition, it was planned to ascertain whether chronic treatment with phosphatidylserine affected possible ECoG changes occurring in aged animals. In comparison to 3 months-old rats, the ECoG activity of 13-15 months-old rats showed spontaneous single or bursts of monophasic and biphasic spikes. In addition, spectrum analysis revealed a significant increase in the power of the lowest frequency band (0.25-3 Hz), accompanied by a decrease in 6-9, 9-12 and 12-16 Hz power. Chronic oral or parenteral treatment with phosphatidylserine gradually reversed the changes in ECoG spectrum power occurring in old rats and produced, at the ECoG level, a distribution pattern of single frequency, bands similar to that observed in young animals.