Simple and Choice Reaction Time Performance in SIV-Infected Rhesus Macaques

It is well established that HIV infection can lead to motor/cognitive disorders in humans. A number of studies have shown that simian immunodeficiency virus (SIV) infection in rhesus macaques parallels many aspects of HIV disease in humans. The purpose of this study was to define further the SIV-infected rhesus macaque as a model of neuro-AIDS. Our objective was to detect movement-related impairments in behaviorally trained, SIV-infected macaques using both simple and choice reaction time tasks. Reaction times (RTs), movement times (MTs), and error types were examined. Nine monkeys were infected with neurovirulent strains of SIVmac, four of which served initially as controls before their inoculation. Seven of the nine monkeys developed simian AIDS within 4 months of inoculation (rapid progressors), while two monkeys survived for more than 1 year postinoculation (slow progressors). Of the rapid progressors, four exhibited slowed reaction times and six showed movement time slowing. One rapid progressor showed evidence of a strategy shift to overcome impaired motor abilities. Monkeys with rapidly progressing SIV-related disease consistently show behavioral abnormalities reflecting underlying neuronal injury. Although the slow progressors also showed RT and/or MT slowing, a role for nonspecific factors related to late-stage simian AIDS could not be ruled out in these cases. The results demonstrate that motor impairments associated with SIV infection in rhesus macaques can be detected using RT and MT measures, further establishing the SIVmac-infected macaque monkey as a viable model of neuro-AIDS.