Ventral striatum

The ventral striatum is part of the brain. In most animals, there is only one part of the striatum, but in humans and other primates, the striatum can be divided by function.The striatum is the largest part of the basal ganglia.
The vental striatum plays a large role in reward recognition (i.e. recognizing when one has received something of value in exchange for a particular action), reinforcement and motivation. Several diseases exhibit a notable pathology of the ventral striatum, such as clinical depression and Obsessive-Compulsive Disorder. It also plays a critical role in addiction.
Ventral striatum at Wikipedia