The putamen (; from Latin, meaning "nutshell") is a round structure located at the base of the forebrain (telencephalon). The putamen and caudate nucleus together form the dorsal striatum. It is also one of the structures that compose the basal nuclei. Through various pathways, the putamen is connected to the substantia nigra, the globus pallidus, the claustrum, and the thalamus, in addition to many regions of the cerebral cortex. A primary function of the putamen is to regulate movements at various stages (e.g. preparation and execution) and influence various types of learning. It employs GABA, acetylcholine, and enkephalin to perform its functions. The putamen also plays a role in degenerative neurological disorders, such as Parkinson's disease. History The word "putamen" is from Latin, referring to that which "falls off in pruning", from "putare", meaning "to prune, to think, or to consider". Until recently, most MRI research focused broadly on the basal ganglia as a whole, for various reasons (e.g. image resolution, rarity of isolated infarct or hemorrhage within the putamen, etc.). However, many studies have been done on the basal ganglia and relevant brain-behavior relationships. In the 1970s, the first single unit recordings were done with monkeys monitoring pallidal neuron activity related to movement. Since then, more extensive neuronal tracing, stimulation, and imaging research methods (e.g. fMRI, DWI) that allow for investigation of the putamen have been developed. Anatomy The putamen is a structure in the forebrain. Along with the caudate nucleus it forms the dorsal striatum. The caudate and putamen contain the same types of neurons and circuits – many neuroanatomists consider the dorsal striatum to be a single structure, divided into two parts by a large fiber tract, the internal capsule, passing through the middle. The putamen, together with the globus pallidus, makes up the lentiform nucleus. The putamen is the outermost portion of the basal ganglia. These are a group of nuclei in the brain that are interconnected with the cerebral cortex, thalamus, and brainstem. Basal ganglia include the dorsal striatum, substantia nigra, nucleus accumbens, and the subthalamic nucleus. In mammals, the basal ganglia are associated with motor control, cognition, emotions, learning, and domain-general functions important for executive functioning as well as support for domain-specific languages. The basal ganglia are located bilaterally, and have rostral and caudal divisions. The putamen is located in the rostral division as part of the striatum. The basal ganglia receive input from