A familiar Latin adage attributed to the second century Roman poet Juvenal states: "Mens sana in corpore sano" (a healthy mind in a healthy body). Nearly 2 millennia later, scientists are still discovering new scientific proof of such timeless wisdom.

The leading Harvard Medical School associate clinical professor of psychiatry, Dr. John J. Ratey, would like you to know that physical exercise offers a number of neurological and even intellectual benefits. Of course, most people were probably already aware of such a claim, at least intuitively if not scientifically, although they may not have fully understood the precise mechanisms underlying such phenomena. In his new book, Dr. Ratey sheds light on the compelling science behind this important topic by elucidating the many ways in which physical activity stimulates various parts of the brain, including, among other components, the brain's own endogenous stem cells. These stem cells, which naturally reside within the brain throughout life, even into the advanced decades of adulthood, are capable of being prompted and directed in their formation of new brain cells by external stimuli such as physical exercise. In "Spark: The Revolutionary New Science of Exercise and the Brain", Dr. Ratey explores the connection not just between physical and mental health, but between specific types of physical exercise and cognitive acuity.

For years, neurophysiologists have already been studying the various factors, of both genetic and environmental origin, that influence the constant re-patterning of neural network connections which in turn provide the cellular basis upon which new information and experiences are processed. Now Dr. Ratey offers further depth and breadth of insight into the cellular and molecular processes of the brain, and into the essential role that physical exercise plays in catalyzing such mechanisms. As the title suggests, the resulting message is nothing short of "revolutionary" in conveying the absolutely critical importance of physical activity.

Among other benefits, Dr. Ratey explains, physical exercise improves the "fitness" of the neocortex, which in turn improves mental agility and mood as well as cognitive processes that require attention, alertness and motivation. But not all physical activity is created equal, and some types are more effective than others at accomplishing specific goals. For the greatest intellectual benefit, aerobic exercise in combination with "complex activity" has been found to maximize "brain power". According to Dr. Ratey, "A fast-paced workout boosts the production of a protein called brain-derived neurotrophic factor. I call it Miracle-Gro for the brain, and physical activity is one of the best ways to release this brain-nourishing protein. A workout at the gym or a brisk walk also seems to build better connections between brain cells. Studies show that regular physical activity may increase the production of cells in the hippocampus, the region of the brain involved in learning and memory. The end result is a brain that's better able to perform in school, at home or on the job." Underlying the continuous replenishing of brain cells are none other than the brain's own stem cells, which are stimulated into action by physical exercise and without which new brain cells and connections between neurons could not be formed.

Dr. Ratey adds, "Aside from elevating endorphins, exercise regulates all of the neurotransmitters targeted by antidepressants. It wakes up the brain and gets it going and improves self-esteem, which is one component of depression. Exercise also boosts dopamine, which improves mood and feelings of wellness. Studies have shown that chronic exercise increases dopamine storage in the brain. The process of getting fit is all about building up your aerobic base. The more you work your heart and lungs, the more efficient they become at delivering oxygen to your body and brain."

As Dr. Ratey further explains, "We need to change the way we think about exercise. We really need to understand that exercise keeps the brain functioning well, and then realize that it also happens to be good for the body. We tend to think about it the other way around, but in fact it readies the cells in the brain to be optimal. We are made to move and people aren't moving anymore."

Devotees of the "mind-body medicine" that was so popular in the 1990s will be particularly interested in this book by Dr. Ratey, which advances the mind-body connection an order of magnitude further by examining with rigorous scientific objectivity the inseparability of physical health and cognitive performance. Even for those people who may not fall into the category of Olympic athletes, however, Dr. Ratey still offers hope by encouraging the reader to find motivation in the knowledge that even moderate exercise can sharpen memory and improve mental function.

Since the publication of Dr. Ratey's book, Harvard Medical School has begun offering seminars on the subject through their Department of Continuing Education. Other universities and health conscious organizations are following the trend.
The book is coauthored with Eric Hagerman and published by Little, Brown & Company, 2008.