First clearly identified by Thomas Willis (1621-1675) in 1664, along with a number of other sub-cortical structures, it is a complex of five bilateral nuclei consisting of the caudate nucleus, putamen, globus pallidus, sub-thalamic nucleus of Luys (ventral thalamus), and the substantial nigra (pars reticula or the reticulate zone) that also include the compact zone (pars compacta). Sometimes included, especially when making cross-species comparisons, are the amygdaloid body (archistriatum), the claustrum, a thin layer of tray matter between the central lobe (lateral sulcus) and the putamen, and the red nucleus (the rubrospinal tract in the midbrain, and not really evident in humans). The globus pallidus and the putamen form the lentiform nucleus (palaeostriatum), and the putamen together with the caudate nucleus make up the corpus striatum (neostriatum). The five nuclei can be grouped into two broad categories based on their input or output connections. The input nuclei are the caudate nucleus and the putamen that receive afferent connections from other parts of the brain other than the basal ganglia (i.e., all areas of the cerebral cortex and the centromedian nucleus of the thalamus). The output nuclei are efferent connections from the globus pallidus (internal segment) and the substantial nigra (reticulate zone) to the thalamus (centromedian and ventral nuclei), and the premotor, prefrontal and motor cortices. Both these output nuclei are inhibitory in function. Following Willis, it was thought for a long time that the basal ganglia was the main part of the brain involved in motor control, a view that changed when Gustav Fritsch (1838-1927) and Eduard Hitzig (1838-1907) identified the motor cortex in 1870.
See Basal ganglia (functions), Cerebral cortex (or pallium), Cerebral (or intracerebral) hemorrhage, Extrapyramidal system, Metabolism, Motor cortex, Nerve Growth Factor (NGF), Parkinson’s disease, Prefrontal cortex (PFC), Prefrontal-frontal-striatal loops, Premotor cortex, Red nucleus, Rubrospinal tract, Tegmentum, Thalamus