Basal Ganglia

http://en.wikipedia.org/wiki/Basal_ganglia

The main components of the basal ganglia are the striatum (also called neostriatum) composed of caudate and putamen, globus pallidus or pallidum composed of globus pallidus externa (GPe) and globus pallidus interna (GPi), substantia nigra composed of both substantia nigra pars compacta (SNc) and substantia nigra pars reticulata (SNr), and the subthalamic nucleus (STN).^[5]

caudate nucleus, putamen, and nucleus accumbens are very similar in their internal structure and are often referred together as the neostriatum and take up the most volume of the basal ganglia

The basal ganglia play a central role in a number of neurological conditions, including several movement disorders. The most notable are Parkinson's disease, which involves degeneration of the melanin-pigmented dopamine-producing cells in the substantia nigra pars compacta (SNc), and Huntington's disease, which primarily involves damage to the striatum.^[1][5]

The basal ganglia have a limbic sector whose components are assigned distinct names: the nucleus accumbens (NA), ventral pallidum, and ventral tegmental area (VTA). VTA efferents provide dopamine to the nucleus accumbens (ventral striatum) in the same way that the substantia nigra provides dopamine to the dorsal striatum. Because there is much evidence that it plays a central role in reward learning, the VTA→NA dopaminergic projection has attracted a great deal of attention. For example, a number of highly addictive drugs, including cocaine, amphetamines, and nicotine, are thought to work by increasing the efficacy of the VTA→NA dopamine signal. There is also evidence implicating overactivity of the VTA dopaminergic projection in schizophrenia.^[6]