Recent quotes:

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.

A man’s best friend: Study shows dogs can recognize human emotions -- ScienceDaily

For the first time, researchers have shown that dogs must form abstract mental representations of positive and negative emotional states, and are not simply displaying learned behaviours when responding to the expressions of people and other dogs.