They commonly have basal and/or apical appendages. It produces extrapyramidal symptoms with necrosis of the cerebral cortex, cerebellum, and basal ganglia. It is frequently associated with lesions of the basal ganglia. Axons from these leave the cortex and connect with subcortical structures including the basal ganglia. Movement disorders are synonymous with basal ganglia or extrapyramidal diseases. The striatum is the largest structure of the basal ganglia. The largest component of the basal ganglia is the striatum. There are some differences in the basal ganglia of primates. The rows of cells develop from stem cells in the basal layer. The structures relevant to the basal ganglia are shown in bold. HPV lesions are thought to arise from the proliferation of infected basal keratinocytes. See main articles on cerebral cortex and basal ganglia for more information. Perivascular microglia are mainly found encased within the walls of the basal lamina. Progress in understanding the functions of the basal ganglia has been slow. The acetylcholinergic system has its neurons located in the pons and in the basal forebrain.