to other addictive stimuli. Bipolar disorder An association has been observed between striatal expression of variants of the PDE10A gene and some bipolar I disorder patients. Variants of other genes, DISC1 and GNAS, have been associated with bipolar II disorder. Autism spectrum disorder Autism spectrum disorder (ASD) is characterized by cognitive inflexibility and poor understanding of social systems. This inflexible behavior originates in defects in the pre-frontal cortex as well as the striatal circuits. The defects in the striatum seem to specifically contribute to the motor, social and communication impairments seen in ASD patients. In mice which have an ASD-like phenotype induced via the overexpression of the eukaryotic initiation of translation factor 4E, it has been shown that these defects seem to stem from the reduced ability to store and process information in the striatum, which leads to the difficulty seen in forming new motor patterns, as well as disengaging from existing ones. Dysfunction Dysfunction in the ventral striatum can lead to a variety of disorders, most notably, depression and obsessive-compulsive disorder. Because of its involvement in reward pathways, the ventral striatum has also been implicated in playing a critical role in addiction. It has been well established that the ventral striatum is strongly involved in mediating the reinforcing effects of drugs, especially stimulants, through dopaminergic stimulation. History In the seventeenth and eighteenth centuries, the term "corpus striatum" was used to designate many distinct, deep, infracortical elements of the hemisphere. Etymologically it is derived from (Latin) "striatus" = "grooved, striated" and the English "striated" = having parallel lines or grooves on the surface. In 1876 David Ferrier contributed decades of research to the subject; concluding that the corpus striatum was vital in the "organization and generation of voluntary movement". In 1941, Cécile and Oskar Vogt simplified the nomenclature by proposing the term striatum for all elements in the basal ganglia built with striatal elements: the caudate nucleus, the putamen, and the fundus striati, which is the ventral part linking the two preceding together ventrally to the inferior part of the internal capsule. The term neostriatum was forged by comparative anatomists comparing the subcortical structures between vertebrates, because it was thought to be a phylogenetically newer section of the corpus striatum. The term is still used by some sources, including Medical Subject Headings. Other animals In birds the term used was the paleostriatum augmentatum, and in the new avian terminology listing