Final answer:
The amygdala is the brain structure highly active during the anticipation of reward, playing a significant role in sexual motivation and the experience of pleasure.
Step-by-step explanation:
The amygdala is a brain structure that is highly active during the pleasurable anticipation of reward. Animal research has shown that limbic system structures such as the amygdala and the nucleus accumbens are crucial for sexual motivation. Damage to these areas can decrease motivation to engage in sexual behavior without affecting the ability to perform the behavior. Moreover, the excitement associated with gambling, which shares similarities with substance addiction, has been linked to the activation of the brain's reward centers that use dopamine, reinforcing the pleasurable experiences and thereby influencing motivation.