Proportions of mitochondria in rat cortical neurons undergoing fission and fusion events determined by DrOF (see Fig. 3). (A) The proportion of activated mitochondria observed to undergo fission. The total number of events for the indicated number of mitochondria was tabulated for eight independent experiments. Statistical significance was calculated using binomial tests for proportions; *, P < 0.05; **, P < 0.002; ***, P < 0.001. Note, the Bonferroni-corrected 95% confidence level is 0.05/6 = 0.0083. (B) The proportion of activated mitochondria observed to undergo fusion. Statistical significance was calculated using binomial tests for proportions (dashed lines are corrected by a factor of one half); *, P < 0.007; **, P < 0.003. (C) Data from B divided by factor of 2 to correct for bias caused by observation of only activated mitochondria.