Coloured magnetic resonance imaging (MRI) scan showing the basal ganglia (yellow) and limbic structures (red) of the brain. As HIV (human immunodeficiency virus) infection has changed from a fatal to a chronic condition, HIV-related brain abnormalities have shifted beyond those of the basal ganglia seen in early patients to the limbic structures. The basal ganglia plays a role in controlling movement. The limbic system plays a role in emotions, learning and the formation of memories. Abnormalities in these areas 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.