Fig. 1: Electrophysiological recordings of ventral CA1 social neurons.
a Schematic of the behavioral paradigm. After 2 h of familiarization between a subject mouse (S) and a stimulator mouse-A in a home cage, the subject mouse was allowed to explore a social arena where the familiar mouse-A and a novel mouse-B were placed. Dotted lines in the arena indicate the borders of social zones. b Heat map of occupancy time during Trial 1 and Trial 2 from a representative session. Note that the map for Trial 2 is rotated and superposed onto that of Trial 1. Comparison of duration spent in the social zone (c) and the discrimination score (d). n = 8 mice; **P = 0.0054, Cohen’s d = 1.40, paired t-test (c) and **P = 0.0078, r = 0.94, Wilcoxon signed-rank test (d). Data from mice that only underwent SDT are shown as gray lines and blank circles, while data from mice that also underwent electrophysiological recordings from vCA1 are shown as black lines and filled circles. e A four-shank silicon probe was implanted in the ventral hippocampus of freely moving mice. Arrowheads in the magnified view indicate the probe track. Scale bars: 1 mm (unmagnified images) and 200 μm (magnified images). f Spike waveforms of two representative clusters. Data recorded from 14 channels at the shank tip are shown. g Spatial firing patterns units shown in f. Unit-#1, a mouse-A cell. Unit-#7, a mouse-B cell. Blue or red dots represent body positions at each spike timing of the cell and gray lines represent the trajectories of the subject mouse during Trials 1 and 2. h Discrimination scores of recorded pyramidal neurons (n = 75 cells). Blue, mouse-A cells (n = 23 cells, 31.1%); red, mouse-B cells (n = 3 cells, 4.0%); gray, neither neurons (n = 48 cells, 64.9%). The P value indicates that the median value of all pyramidal neurons was significantly different from zero (r = 0.41, Wilcoxon signed-rank test). i Z-scored firing rates of mouse-A cells and neither cells during social trials (Trial 1 + 2; left) and the control trial (Trial 3; right). Trial 1+2: Unit Type × Area, F(1,69) = 96.6, P = 9.5 × 10−15, η2 = 0.35, partial η2 = 0.58; ***P = 3.3 × 10−9, r = 0.70 (A), 9.3 × 10−8, r = 0.63 (B). Mouse-A: ***P = 9.6 × 10−10, r = 0.73 (A vs B), 2.1 × 10−7, r = 0.62 (Center vs B); Neither: **P = 0.0081, r = 0.31 (A vs Center), *P = 0.024, r = 0.24 (Center vs B). Trial 3: UnitType × Area, F(1,69) = 0.42, P = 0.52, η2 = 0.0040, partial η2 = 0.0061. All statistical tests are two-way repeated-measures ANOVA and Tukey–Kramer multiple comparison tests. j Firing timings of the two units shown in Fig. 1f, and relative social distance of the subject mouse. Shaded periods indicate that the subject was in the social zone around mouse-A (blue) or mouse-B (red). Ticks and filled circles represent spike timings of Unit #1 (blue) and #7 (red). k Correlations between social preferences and directional social preferences of pyramidal neurons (n = 75 cells). Whole arena, r = 0.65, P = 3.9 × 10−10; center zone, r = 0.35, P = 0.0021. l Comparison of directional social preferences. Comparison between neither vs mouse-A cells: **P =0.0022, r = 0.36, Wilcoxon rank sum test. Comparison between each group vs zero: mouse-A cells in whole arena, ***P = 3.7 × 10−4, r = 0.51 and mouse-A cells in center zone, *P = 0.026, r = 0.46, Wilcoxon signed-rank test. ns, not significant. m Preferred directions and mean resultant vectors of neither cells and mouse-A cells. The black arrow direction indicates mean direction preference of all neither cells and mouse-A cells. Arrow lengths of mean resultant vectors indicate the direction concentration parameter, kappa. Neither: n = 48 cells, mean direction = 317.0°, P = 0.31, V test for circular uniformity against 0°; mouse-A: n = 23 cells, mean direction = 10.6°, ***P = 1.3 × 10−6, V test for circular uniformity against 0°.
