Fig. 1. Object placement induced a complex population response in CA1.

a Representative firing rate distribution maps (rate maps) of neurons recorded from proximal, middle, and distal bands of CA1, showing responses to familiar objects placed in the recording box. Maps for the same cell across four trials are arranged in rows, with animal and cell IDs indicated on the left. Color is scaled to maximum peak rate of four trials. Text above each map indicates the peak rate of that trial. Circles represent objects. Obj−, trial without objects; Obj+, trial with two familiar objects. b Distribution of cells in response to object placement across three CA1 bands. Numbers indicate active place cells in each category. Proportion of cells with firing rate changes: pCA1, 57.94%, mCA1, 50.41%, and dCA1, 60.58%; chi-square test, χ² = 15.640, P < 0.001, Cramer’s V  = 0.094; Holm–Bonferroni post hoc tests, ***P < 0.001. c Heatmaps showing PVC of all putative pyramidal neurons recorded from each CA1 subregion between trials with or without objects (top two rows), as well as changes in PVC between condition pairs (bottom row). Heatmap bins correspond to spatial bins in rate maps. Color scales are indicated on the right of each row. Small circles represent objects, large circles indicate object regions. d Degree of changes in PVC as a function of distance to the objects (mean ± SEM) in each CA1 subregion, with colored dots representing data from individual spatial bins. Two-way ANOVA, distance: F (16, 1131) = 64.191, P < 0.001, η² = 0.476; band: F (2, 1131) = 24.107, P < 0.001, η² = 0.041; distance × band: F (32, 1131) = 4.963, P < 0.001, η² = 0.123. e Boxplots showing degree of changes in PVC between trial pairs, for spatial bins inside and outside the object region, with outliers omitted. Bins inside object region: median (25%–75% percentile), pCA1, 0.199 (0.171–0.228), mCA1, 0.215 (0.174–0.285), and dCA1, 0.185 (0.154–0.239). Bins outside object region: pCA1, 0.096 (0.065–0.150), mCA1, 0.063 (0.026–0.107), dCA1, 0.075 (0.042–0.130). Population responses inside and outside the object region were significantly different: two-way ANOVA: band: F (2, 796) = 4.496, P = 0.011, η² = 0.011; object region: F (1, 398) = 381.672, P < 0.001, η² = 0.490; band × object region: F (2, 796) = 28.513, P < 0.001, η² = 0.067. Holm–Bonferroni post hoc tests for bins outside the object region, ***P ≤ 0.001.