Figure 1: Sensory stimulation induces hippocampal theta oscillations. (a) Representative field recordings obtained from the hippocampal fissure in a urethane-anaesthetized rat at rest (blue recording) and upon sensory stimulation (red trace). (b) and (c) show the spectrograms and the power spectra, respectively, of the traces shown in (a). The blue power spectrum corresponds to the recording at rest, and the red power spectrum corresponds to the recording upon sensory stimulation. The inset in (c) shows the quantification of the change in power upon sensory stimulation, compared with basal hippocampal activity. *Indicates a significant difference compared to the control ( ; Wilcoxon signed-rank test).