Basal ganglia Cho/Cr ratios obtained four weeks after infection in animals that subsequently developed SIV encephalitis and those that did not. Error bars represent the standard error of the mean (SEM). A t test was performed assuming equal variances between the two groups of animals. A test to determine whether the variances between the two groups of animals were different proved not to be significant. Animals that later were found to have SIVE (encephalitic) (n = 2) had higher Cho/Cr compared to the other animals (n = 6) (P = 0.022).