Our study was performed in rats under urethane anesthesia using RPO stimulation—a commonly used model that allows experimental control over forebrain oscillations without behavioral confines (McNaughton et al. 2007)—and showed that the same experimental paradigm can be applied to investigate HC theta and PFC slow oscillations. Importantly, the appearance of field potential traces and the spectral representation of the rhythmic PFC signal showed essential similarities with HC theta rhythm, and were drastically different from wide-band delta activity. Furthermore, RPO stimulation intensity effectively controlled the frequency and amplitude of both oscillations. Just as the frequency of spontaneous theta rhythm which appears at the lower end (~4 Hz) of the theta band can be increased up to 7–8 Hz by RPO stimulation (Li et al. 2007; Ly et al. 2013; McNaughton and Sedgwick 1978), the frequency of the 2–5 Hz PFC oscillation which spontaneously occurs at ~2 Hz (Kiss et al., 2011a, 2011b) can be increased by RPO stimulation to generate sharp spectral peaks across the entire 2–5 Hz range found in awake rats (Fujisawa and Buzsaki 2011). We also found that,
