Final answer:
Stimulants are drugs that increase neural activity and can affect the dopamine neurotransmitter system. Examples include methamphetamine, caffeine, cocaine, and amphetamine.
Step-by-step explanation:
Stimulants are drugs that tend to increase overall levels of neural activity. Examples of stimulants include methamphetamine, caffeine, cocaine, and amphetamine. These drugs stimulate the brain and increase alertness and wakefulness. They can have effects on the dopamine neurotransmitter system, which is associated with reward and craving, leading to their abuse liability.