From Wikipedia on 20-May-2013
Desire is a sense of longing for a person or object or hoping for an outcome. The same sense is expressed by emotions such as “craving” or “hankering”. When a person desires something or someone, their sense of longing is excited by the enjoyment or the thought of the item or person, and they want to take actions to obtain their goal. The motivational aspect of desire has long been noted by philosophers; Hobbes (1588–1679) asserted that human desire is the fundamental motivation of all human action.
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A 2008 study entitled “The Neural Correlates of Desire” showed that the human brain categorizes any stimulus according to its desirability by activating three different brain areas: the superior orbito-frontal, the mid-cingulate, and the anterior cingulate cortices.
While the “neuroscience of happiness and well-being is still in its infancy”, research on the “distant cousins” of pleasure and desire show that reward is a key element in creating both of these states. Studies showed that a chemical called dopamine is the brain’s “pleasure chemical”. Research also shows that the orbitofrontal cortex has connections to both the opioid and dopamine systems, and stimulating this cortex is associated with subjective reports of pleasure.