This study will examine whether antiretroviral therapy (ART) is sufficient to halt the detrimental impact of HIV on the brain when initiated within weeks of infection. We will enroll participants who start ART within days of viral exposure. We will examine longitudinal multimodal imaging outcomes (resting state fMRI, diffusion tensor imaging, and structural volumetrics) of people with acute HIV infection, demographically-similar people with chronic HIV infection, and people without HIV infection. Additionally, evidence of persistent neural injury despite ART instituted during acute infection would identify key mechanisms of HIV neuropathogenesis and potential high-impact targets for clinical interventions. In addition to collaborators in Thailand, this study is being co-led by Dr. Robert Paul at University of Missouri.