Fig. 1

A Schematic representation of the behavior apparatus and experimental timeline used in contextual fear conditioning (CFC). B Representative photomicrographs of DCX + cells (green) in the DG (DAPI; blue) of rats in the sedentary + vehicle (SED + VEH), runner + vehicle (RUN + VEH), sedentary + TMZ (SED + TMZ), and runner + TMZ (RUN + TMZ) groups. C DCX + cells/mm² after sedentary control or running and vehicle or TMZ treatment. Upper graph shows individual data points in swarm plots with means (± SD; gapped vertical line). Lower graph shows effect size (Cohen’s d) as a black circle with vertical lines and gaussian distributions for the bootstrap 95% CI. Neurogenesis was substantially increased by running, and conversely, was decreased by TMZ. Moreover, this effect of TMZ was most striking in the running groups, with the RUN + TMZ group exhibiting unchanged neurogenesis relative to the SED + TMZ group, but reduced neurogenesis relative to the RUN + VEH group. D % Freezing in CFC training prior to manipulation of neurogenesis. Upper graph shows individual data points in swarm plots with means (± SD; gapped vertical line). Lower graph shows effect size (Cohen’s d) as a black circle with vertical lines and gaussian distributions for the bootstrap 95% CI. All 4 groups exhibited equivalent levels of freezing during conditioning. E % Freezing during CFC testing after manipulation of neurogenesis. Upper graph shows individual data points in swarm plots with means (± SD; gapped vertical line). Lower graph shows effect size (Cohen’s d) as a black circle with vertical lines and gaussian distributions for the bootstrap 95% CI. Freezing was significantly reduced in the RUN + VEH group relative to the SED + VEH group with no other significant differences being present. The results show that running causes forgetting relative to sedentary control, and that this effect is blocked by TMZ, indicating that the forgetting effect is dependent on increases in neurogenesis