Figure 3.

Phase-locking activities of the lateral habenular and hippocampal neurons. A–C, Examples of unit activity of neurons in the lateral habenula (red, A) and a pyramidal cell (light blue, B) and an interneuron in the hippocampus (dark blue, C) showing in the raster plots (top panels) and in the phase histogram of the firing probability within the time window made by subdividing each theta cycle (360°) into 20 bins (bottom panels). Data were replicated over two theta cycles for visual clarity. D–F, Distribution of log-transformed Rayleigh's Z value, a statistical value used to evaluate the significance of phase locking for the lateral habenular neurons (D), the pyramidal cells (E), and interneurons (F) in the hippocampus. Dashed black lines indicate the p = 0.01 significance thresholds, which were used to identify the phase-locking neurons. G–I, Changes in the mean firing rate of the recorded neurons showing phase locking (solid lines) and those without phase-locking activity (dotted lines) in the lateral habenula (G) and hippocampus (pyramidal cells in H and interneurons in I) across the brain states. Error bars indicate SEMs. J–L, Scatter plots showing the preferred phase of the phase-locking neurons against the spike width in the lateral habenula (J) and hippocampus (pyramidal cells in K and interneurons in L). M–O, Histograms showing the frequency of the theta phase preferred by the phase-locking neurons recorded in the lateral habenula (M) and hippocampus (pyramidal cells in N and interneurons in O). Arrows and arrowheads in M indicate the neuronal groups in the lateral habenula preferring the ascending and descending phases of the theta cycle, respectively.