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
These six layers of the neomammalian brain work interdependently to process neurological messages at an extremely fast and high-quality level . These six layers are only found in the modern day human brain; however, other higher order mammals have features of these layers that give allow them to have a high cognitive processing ability.