This chapter has only scratched the surface of the organization and functions of the human brain. Even with all of our knowledge of the human brain, and with all of the sophisticated new research tools, we still cannot answer the question “What is consciousness?”

The word “consciousness” is used in everyday language to refer to being awake in contrast to being asleep or in a coma. Here we are referring to being mentally aware of yourself, your environment, and events going on around you in such a way that you can plan for future events and make decisions based on experience, evidence, value systems, and predicted consequences. Speculations about consciousness have been the realm of philosophers, but we are getting closer to a neurobiological understanding.

One requirement for conscious experience is a perception of self that can be integrated with information from the physical and social environment and information from past experience. The basis for a perception of self derives from the huge amount of somatosensory and visceral information that comes from all parts of the body. This information is used for motor control and for homeostatic regulation. It enables animals to find food, seek mates, seek warmth, avoid cold, avoid danger, and so on. Different types of this afferent information go to appropriate control and regulatory systems in the brainstem and forebrain. But these diverse sources of information also go to the insular cortex. The insular lobe appears to integrate physiological information from all over the body to create a sensation of how the body “feels.” Thus when an animal’s actions restore homeostasis, it “feels” better, and this is motivation to do the right thing for well-being.

In humans and the great apes, the insular cortex is greatly expanded and its circuitry communicates with parts of the brain involved in planning and decision making. In imaging studies, the insular lobe is activated by a great diversity of situations that involve strong feelings such as pleasure, disgust, humor, pain, lust, craving, humiliation, guilt, or empathy. Damage to the insular lobe causes apathy, loss of the ability to enjoy music, loss of sexual responsiveness, and even loss of the ability to distinguish good food from spoiled food. Humans and the few other species (great apes, elephants, and some marine mammals) that have an expanded insular lobe are the only species that can recognize themselves in a mirror. Could it be that this very discrete part of our brains and its circuitry are the neurobiological basis for self-awareness?