Nature and nurture
New techniques and insights reveal the amazing complexity of the human brain
Editor’s Note: A professor of Pharmacology, Levitt studies the molecular and developmental basis of neuropsychiatric disorders.
Early experiences, both in the womb and after birth, can have profound effects on the way in which genes and their protein products orchestrate the formation of circuits that control our mood, our ability to endure stress, our thought processes, our ability to learn new information, and our recall of important memories. It is the combination of these forces – genetic and environmental – that underlies the development of devastating brain disorders such as schizophrenia and autism, and functionally milder ones such as attention deficit hyperactivity disorder (ADHD).
While I have been studying some aspect of brain development since my college days, I began the process of integrating nature and nurture in 1986, after a visit to the intensive care nursery at the Medical College of Pennsylvania, where I was a young assistant professor. My colleagues wanted me to get involved in a new research project to study the effects of prenatal exposure to cocaine on brain development. I resisted; drug exposure research would only distract me from my mission of finding and describing neuro-development genes. Well, the images of the infants, struggling in a new world, possibly carrying the legacy of an altered wiring diagram for the rest of their lives, was more powerful than I had imagined.
I began a new scientific journey, transforming my own laboratory into one in which we became more and more engaged in multidisciplinary efforts with other scientists to investigate the interaction of genetic and environmental factors in the developing brain, how genetic susceptibility translates into disorders, and how intervention can alter the course of development to improve outcomes.
Donald Hebb, who proposed our modern view of the biological mechanism of learning and memory in the 1940s, once made the analogy that the debate about whether nature or nurture is more influential on brain development and functioning is like arguing about whether the length or the width of a rectangle is more relevant in determining its area. Like the rectangle, the trick regarding brain development is to determine how nature and nurture interact to influence the emerging properties of developing brain systems.