Hou et al. (2012) revealed that the DAT expression level of the striatum was significantly decreased and they suggested IAD is associated with dysfunctions in the dopaminergic brain systems. Kim et al. (2011) showed reduced levels of dopamine D2 receptor availability in the subdivisions of the striatum including the bilateral dorsal caudate and right putamen in individuals with IAD. The gene discussed is DRD2; the disease is internet addiction disorder.