Functional Brain Systems: Reticular Formation

The reticular formation is a complex network of gray and white matter spread across the core of the brainstem.

It is roughly divided into three paired columns of nuclei — the median or raphe, the medial, and the lateral — connected to the limbic system, different parts of the brain, and the spinal cord.

The reticular formation has both sensory and motor portions.

The sensory part is called the reticular activating system — RAS. It projects to the cerebral cortex and also through the thalamus.

The most critical function of the RAS is consciousness. Inactivation of the RAS induces sleep, while damage to it results in coma.

The RAS particularly facilitates attention and alertness. One example is concentrating on a cucumber while chopping it with a knife to carefully protect the fingers.

The RAS can process visual and auditory stimuli but not olfactory ones.

The motor portion of the reticular formation assists in coarse limb movements and regulates visceral motor functions.