Individual (bars) and averaged (line) normalized gross motor activity measurements of five monkeys before, 1, 2, and 3 months after inoculation with SIV. At 3 months p.i. the decrease in motor activity reaches statistical significance when compared with preinoculation levels (ANOVA with post hoc t test, P < 0.05. Comparisons are made within subjects, n = 5 for preinoculation, 1 and 2 months. Monkey no. 264 was sacrificed at 11 weeks after SIV inoculation, therefore n = 4 at 3 months).