Fig. 4.

Correlation between performance in the contextual fear-conditioning task and brain levels of protein carbonyls. Individual data for contextual fear conditioning and brain protein carbonyl contents for the 8-month-old control mice were plotted and exhibited a significant negative correlation (Pearson's correlation coefficient, γ =-0.76, P < 0.005). The levels of protein oxidation were expressed as nmol of carbonyl per mg of soluble extracted protein, and contextual fear conditioning was scored as percentage of freezing duration per min (mean ± SEM of 12 mice). Note that deleting the two outlying points still resulted in a significant correlation, γ = -0.74, P < 0.005.