Longitudinal cerebral Cho/Cr ratios in SIV-infected macaques. Data were derived from MR spectra from 3 cerebral locations. BG represents scans taken in the basal ganglia region, FC represents scans taken in the frontal cortex, and CS represents scans taken from the centrum semiovale. Error bars represent the standard error of the mean (SEM). Asterisks represent statistically significant metabolite ratio differences compared to pre-infection values. All eight animals were scanned at every time point through 90 dpi. After this time: 270 dpi represents 6 animals, 390 dpi 5 animals, 450 dpi 3 animals, 510 dpi 4 animals, 570 dpi 3 animals, and 720 dpi 4 animals. Cho/Cr values obtained from the frontal cortex were significantly higher than baseline values at two weeks post inoculation (* P < 0.05) and was followed by a sharp decline to below baseline at 4 weeks post inoculation (** P < 0.01). Cho/Cr in the other regions displayed similar, albeit non-significant changes in the first four weeks following infection. The inset plot in the Cho/Cr figure expands the first 4 weeks after infection. For all of the regions ANOVA revealed no statistically significant changes in the chronic phase of infection (>28 dpi).