henry copeland:

Scientists identify brain circuit that drives pleasure-inducing behavior: Surprisingly, the neurons are located in a brain region thought to be linked with fear -- ScienceDaily

The researchers found that five of these populations stimulate reward-related behavior: When the mice were exposed to light, the mice repeatedly sought more light exposure because these neurons were driving a reward circuit. These same populations all receive input from the positive emotion cells in the BLA.
- www.sciencedaily.com