The primary sites of serotonin release in the brain, the raphe nuclei, are found near the midline of the brainstem in the reticular formation. One of the largest dopamine-producing areas in the brain, the ventral tegmental area, is located in the reticular formation, as is the locus ceruleus, which is the largest collection of noradrenergic neurons in the brain. The reticular formation is home to several groups of cells that produce neurotransmitters these neuronal populations have extensive connections throughout the central nervous system and are involved in the regulation of activity throughout the brain. Of the numerous cell groups and tracts found throughout the reticular formation or connected to reticular formation neurons, some worth noting are nuclei involved in neurotransmitter production, nuclei associated with the cranial nerves, descending tracts involved in modulating sensory and motor functions, and ascending tracts integral to arousal and consciousness. However, it is now clear that the reticular formation is highly organized, just very intricate and complex. Due to the heterogeneity of the structure, as well as to the fact that there are not clear boundaries between the nuclei within the reticular formation, it was originally thought to lack organization. The fibers that traverse the reticular formation give the region a net-like appearance, which is where it gets its name ( reticular means net-like).

The reticular formation is a very diverse structure that contains various nuclei along with numerous ascending and descending tracts. What is the reticular formation and what does it do?

As the reticular formation is found at the core of the tegmentum, it too runs along the length of the brainstem. The tegmentum is a heterogeneous section of neural tissue that extends vertically through the brainstem, making up the portion of the brainstem that sits between the ventricles and surface structures like the basal pons and the pyramids of the medulla. The reticular formation is found in the brainstem, at the center of an area of the brainstem known as the tegmentum.

Simple image brain stem function