The nature and extent of number processing (NP) abilities in HIV is unclear. To date there have been no systematic studies examining NP in this population. The goal of the present study is to provide a comprehensive picture of NP abilities in people living with HIV. The general hypothesis is that patients with HIV will show deficits in NP abilities because of the known effects of HIV on the basal ganglia and the dorsolateral prefrontal cortex (DLPFC) circuit that includes the posterior parietal lobes. The same neural circuitry is involved in a second cognitive domain - visuospatial processing. This study will compare the nature of NP and visuospatial dysfunction in HIV. Participants with HIV and control adults will be examined on NP (number reasoning, number transcoding, number bisection, spatial number orientation, and arithmetic facts retrieval) and visuospatial abilities (spatial reasoning, spatial exploration, visuospatial problem solving, and constructional praxis) measured by standardized neuropsychological tests and by tests derived from the cognitive neuroscience literature. This comparison will shed light on the nature of NP in this neurodegenerative condition and will determine whether selective visuo-spatial deficits have impact on number processing domain. This distinction will guide further research leading to interventions to improve daily function in these cognitive domains in HIV. [unreadable] [unreadable] [unreadable]