Fluoxetine treatment increases interneuron dynamics in aged mice. A, Experimental time line. B, Average cell FF at different ages. Each circle represents an individual cell. Dashed line marks the experimentally determined threshold (FF = 0.35) for a dynamic cell. The nontreated cells are also shown in Figure 1D. Fluoxetine treatment from 3 to 6 months has no effect on the average cell FF compared with 6 month controls (p = 0.13, by bootstrap, n = 14 for untreated, n = 8 for treated). Treatment from 6 to 9 months compared with 9 month controls significantly increased the average cell FF (*p = 0.043, by bootstrap using Holm–Sidak's test with α = 0.05 to correct for multiple comparisons, n = 10 for untreated, 8 for treated), as did treatment from 3 to 9 months (*p = 0.043, by bootstrap using Holm–Sidak's test with α = 0.05 to correct for multiple comparisons, n = 10 for untreated, 6 for treated). However, the longer treatment resulted in FF improvement for a larger fraction of animals (25% for 3 months vs 67% for 6 months). Error bars represent SD of the bootstrapped population.