Brain
There are dozens of other chemical neurotransmitters that are used in more limited areas of the brain, often areas dedicated to a particular function. Serotonin, for example—the primary target of antidepressant drugs and many dietary aids—comes exclusively from a small brainstem area called the raphe nuclei. Norepinephrine, which is involved in arousal, comes exclusively from a nearby small area called the locus coeruleus. Other neurotransmitters such as acetylcholine and dopamine have multiple sources in the brain, but are not as ubiquitously distributed as glutamate and GABA.
Adult neurogenesis
More attention has been given to neurogenesis in the dentate gyrus than in the striatum. In rodents, many of the newborn dentate gyrus neurons die shortly after they are born, but a number of them become functionally integrated into the surrounding brain tissue. The amount of neurons born in the human hippocampus remains controversial; some studies have reported that in adult humans about 700 new neurons are added in the hippocampus every day, while other studies show that adult hippocampal neurogenesis does not exist in humans, or, if it does, it is at undetectable levels. The role of new neurons in adult brain function thus remains unclear. Adult neurogenesis is reported to play a role in learning and memory, emotion, stress, depression, response to injury, and other conditions.