Figure 5: CA2 spatial correlations decrease with time and decrease further with social stimulation.

Spatial correlations for CA2 (a) and CA1 (b) place cells for control, familiar animal and familiar object (stuffed animal toy) conditions. Spatial correlations were calculated between the first and second sessions (A1–A2), the second and third sessions (A2–A3), the third and fourth sessions (A3–A4) and the first and fourth sessions (A1–A4). For both CA2 and CA1, temporally adjacent sessions (A1–A2, A2–A3 and A3–A4) had significantly greater spatial correlations than temporally distant sessions (A1–A4). These significant effects of time (two-way ANOVAs: effect of time, CA2 (n=96 cells): F(1,378)=15.2, P<0.001; CA1 (n=253): F(1,1066)=11.9, P=0.001) are indicated with ***P<0.001 and **P=0.001. (a) CA2 place cells remapped in response to social stimulation, as evidenced by significantly lower spatial correlations in the social stimulation condition than in the other conditions (repeated-measures ANOVA: effect of condition, F(2,93)=8.5, ***P<0.001; control: n=11 neurons, familiar animal: n=47, familiar toy: n=38). In addition, for A1–A4 comparisons, spatial correlations were significantly lower for the social condition than the other conditions (one-way ANOVA: F(2,93)=7.4, ##P=0.001; n-values same as above). (b) CA1 place cells did not show significant remapping in response to social stimulation (repeated-measures ANOVA: effect of condition, F(2,250)=0.6, P=0.6, control: n=26 neurons, familiar animal: n=134, familiar toy: n=93). Error bars are s.e.m.