The prior description of the brain was based on a cross-section of the brain associated with looking at a person’s profile. On the other hand, looking at the brain from above, one discerns two cerebral hemispheres. These two hemispheres are connected by a structure called the corpus callosum (“thick body”). The function of the corpus callosum is to provide a way for the two hemispheres to communicate with each other.
In the vast majority of people, the corpus callosum is intact. Consequently, sharp differences between the way the two different hemispheres work are not usually evident. However, in a very small number of people, the corpus callosum has been cut as a treatment for intractable epilepsy. It is possible in such patients to study the different ways the two hemispheres work.
It is evident from studies of subjects with a severed corpus callosum that the right hemisphere mediates nonverbal patterning—the kind of mental functioning required in drawing, making up a melody, dancing, and creating visual images. The right hemisphere is sometimes called the “romantic” hemisphere.
The left hemisphere mediates verbal and mathematical thinking—the kind of mental functioning required in writing, talking, scientific analysis, working on an algebra problem, and so forth. The left hemisphere is sometimes called the “logical” hemisphere. The right side of the brain does know what the left side is doing if the corpus callosum is intact—as it usually is.
The Endocrine System: Moods and Your Glands
You have a set of glands in your body that have a lot to do with your moods, your emotional states, and your behavior in general. Working together, these glands are called the endocrine system. The glands themselves are called endocrine glands because they secrete their substances directly into the bloodstream without ducts. (Endo means “within” or “inside.” In contrast, exocrine glands, such as salivary or digestive glands, secrete their substances “outside” of the bloodstream.)
The substances secreted by the endocrine glands are called hormones. These, like neurotransmitters, act as chemical messengers. The pineal gland is a tiny gland located nearly in the center of the brain. It is called “pineal” because it is shaped something like a pine cone. Of historical interest is the fact that the philosopher René Descartes suggested, perhaps because it is small and centered, that the pineal gland is the place where the soul interacts with the body.
Today’s research indicates that the pineal gland secretes a hormone called melatonin. This hormone plays a role in controlling the biological timetable for sexual maturation. Another of its functions is to regulate the sleep cycle.