DRD2 and Parkinson disease: Despite this, current drug treatments often fail to remediate cognitive impairment in schizophrenia (e.g. (Leeson et al. 2009)); in the case of PD, the same drugs that restore voluntary movement by increasing dopamine (DA) tone in the dorsal striatum may even contribute to impairments in reversal learning, perhaps by “overdosing” the relatively intact ventral striatum with DA or DA D2-like receptor (D2R) agonists (Swainson et al. 2000).