The ventral striatum, including the head of the caudate nucleus and the nucleus 
accumbens, is a putative target for deep brain stimulation (DBS) in the 
treatment of obsessive-compulsive disorder (OCD) and major depression (MD). 
However, the respective roles of these structures in the pathophysiology of OCD 
and MD remain to be clarified. To address this issue, DBS of the ventral 
striatum was tested in 2 patients with severely distressing and intractable 
forms of OCD and MD. Comparisons of clinical outcomes and anatomical data on 
electrode positioning showed that caudate nucleus stimulation preferentially 
alleviated OCD manifestations, whereas nucleus accumbens stimulation improved 
depressive symptoms. These findings suggest that the caudate nucleus and nucleus 
accumbens participate differently in the pathogenesis of both of these 
psychiatric conditions.