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.
Neomammalian brain
Through comparing the three different sections of MacLean's Triune Theory, neuroscientists have been able to account for the complexity of the human brain in comparison to reptiles, birds and other lower order mammals . Animal scientists have dissected a vast array of organism’s brains and through comparison ultimately concluded that the cerebral cortex (neomammalian Brain) has a different column structure to other organisms’. The discovery of the six layered neomammalian brain has allowed neuroscientists to research into their differing roles, and how each function interdependently to allow for complex thought to occur. The six layers have been separated into three different sections according to the role they play in the survival of a human.