Brain

The brain is a pinkish-grey, wrinkled organ that fills the skull — looking, for all the world, like a huge walnut. It is hard to believe, from its appearance, that this ugly lump of jelly contains the mechanisms of thought, perception, will, and consciousness, that it is the seat of our personality. Its 100,000 million nerve cells, each with an average of 100,00 connections from other neurons, makes the human brain the most complicated and least understood object in the known universe. The vertebrate brain is the large anterior portion of the central nervous system . The "cranial vault" of the skull encases the brain in most vertebrates. In invertebrates, the enlarged and specialized anterior ganglion of the central nervous system is often referred to as a brain, although not all scientists regard it as a true brain.

Vigilance disorder

Primary disorder of vigilance is a term for a syndrome that includes poor attention and concentration as well as difficulties staying awake. The term is not recognized as an official diagnosis by the American Psychiatric Association, but some experts believe it represents a fairly well defined set of behaviors. People with vigilance disorder tend to fidget, yawn and stretch, and appear to be hyperactive in order to remain alert; they typically have kind and affectionate temperaments. The condition appears to be inherited and gets worse with age; it is treatable with stimulants.