When you have to have the newest tech gadget or go skydiving for the first time, your ventral striatum may be the culprit.  The ventral striatum is also the section of the brain where drug and alcohol use induces the release of dopamine. 

In addition, compared to people without ADHD, people with ADHD have reduced activation in the ventral striatum when anticipating rewards. 

http://www.msnbc.msn.com/id/25370740/