Coloured magnetic resonance imaging (MRI) scans showing atrophy (loss) of brain tissue in patients with HIV/AIDS (human immunodeficiency virus/acquired immunodeficiency disease). In the early stages of infection HIV particles enter the brain and stimulate the production of cytokines, which are toxic to nerve cells, leading to cell death. This leads to neurocognitive dysfunction, that can include difficulties in concentration, psychomotor slowing, and impaired information processing, and in later stages of the disease can lead to HIV-associated dementia.