Figure 2.

Theta phase modulates genuine high-frequency oscillations >100 Hz in the hippocampus. A, Comodulation map. B, Power spectral density in dB scale. Notice theta peak and a power peak ∼140 Hz. Inset shows power of fast oscillations in absolute scale (mV²/Hz). C, Multiunit activity as a function of HFO phase. D, Left, Mean HFO amplitude (top) and multiunit activity (bottom) as a function of theta phase. Right, Normalized HFO and multiunit activity vs theta phase. E, LFP averages triggered by HFO peaks (top) and spike times (bottom). The results shown in this figure were obtained from a representative LFP recorded from CA1 stratum oriens-alveus in a freely behaving rat during active waking.