Fig. 1: Effect of infantile spatial experience on adult OPR performance.

A General procedure: During infancy, pups of the Spatial-experience group (n = 17, red) were placed in an arena with two identical objects for 5 min and, after a 5 min break, re-entered to the arena but this time, one of the objects was displaced to a new location. Different spatial configurations and objects were used at the four exposures on PD18, 20, 22, and 24. For the Object-experience group (n = 17 rats, green), instead of a change in object location, one of the objects was replaced by another, in the second 5 min period. The No-experience group (n = 18 rats, grey) had no arena visits during infancy. At adulthood (~PD80), all groups were tested on a classical object-place recognition (OPR) task with a 3 h delay between encoding and retrieval testing. B OPR memory (mean ± SEM discrimination ratios during 1st minute of retrieval phase, dot plots overlaid) at adulthood testing. Only rats with spatial experience during infancy displayed significant OPR memory ^###P = 0.000 for one-sample t-test (two-sided) against chance level *P = 0.023 and **P = 0.004 for pairwise comparisons (two-sided t-test) between experimental groups. C Grey shaded shows the OPR memory performance (mean ± SEM discrimination ratios during 1st minute of retrieval phase, dot plots overlaid) at adulthood and the procedure of additional control experiments (right). For the rats of the Stationary-experience group (n = 12 rats, yellow) both the objects and their spatial configuration remained unchanged at the two visits of each infantile exposure. Procedures for the Context-change group (n = 12 rats, purple) were the same as for the Spatial-experience group, except that OPR testing at adulthood was performed in an entirely different context. Whereas the Stationary-experience group showed the same enhanced OPR performance as the Spatial-experience group, the Context-change groups did not show significant OPR memory (bottom). ^###P = 0.000 for one-sample t-test (two-sided) against chance level; *P < 0.05 for pairwise comparisons (two-sided t-test) between experimental groups. (see Figs. S1, S4 for discrimination ratios for entire 5-min retrieval phase). Source data are provided as a Source Data file.