connection July / August 1998

Early Stimulation Linked
to Better Brain Development

The nature-versus-nurture debate just got a new twist: it may not be a matter of one or the other, but a matter of how the two are connected that explains our capacity to learn and function.

Parents read bedtime stories to their infant children in hopes of `nurturing' their growing brains and improving their learning abilities. But a group of Medical School researchers have discovered that what they may be doing is helping `nature' along.

Dr. Paul Neumann, Professor of Anatomy & Neurobiology, and his colleagues have found there is a biological reason for why early stimulation can help improve a child's capacity to learn, remember and perform other functions—reasoning that goes beyond the common belief in scientific circles. "Now it appears that early stimulation and brain activity can not only influence mental ability, they can influence the brain's actual development," says Dr. Neumann.

The researchers discovered a mutation in a gene long known to be involved in learning and memory — adenylyl cyclase type 1 (Adcy1). They found it in a rare strain of mice, but while studying the mice, they discovered something new about the brain's early development.

Most mice explore the world through their whiskers, each of which has a corresponding channel in the brain through which it sends signals. These channels, or "barrels," relay information to other parts of the brain about the mouse's environment. But the strain of mice Dr. Neumann studied were "barrelless," which he expects makes them less able to distinguish between different objects and stimuli around them.

Two years ago, the group, including Dalhousie's Raja Abdel-Majid, Wey Leong, Donald Smallman, and Drs. Neumann, Alan Fine, Melanie Dobson, and Duane Guernsey, mapped the gene responsible for the absence (or development) of barrel formation. After finding the location, they identified the mutation in Adcy1, a gene necessary for barrel formation, in barrelless mice.

Until now, the common belief in the scientific community was that each area of the brain was formed according to how a person's genes instructed them to form, a process known as induction. But Dr. Neumann says since Adcy1 is responsible for problems in the sensory system of barrelless mice (which don't appear until several days after they're born) and is also known to play an important role in brain cell activity, this research suggests the brain's functional patterns depend on brain activity as well as induction.

Dr. Neumann says the learning and memory influenced by the Adcy1 gene doesn't stop at grammar and multiplication tables. The gene also influences how well the brain learns to perform its other functions. He compares this to muscle development: the more you stimulate or use a muscle, the stronger it becomes. He argues the brain is no different.

"Our brains are plastic—they can change and improve with activity," he says. "Plasticity is an important phenomenon that underlies learning and memory and also recovery from brain injury. This work demonstrates that there is also a large degree of activity-dependence in the final stages of brain development."

While the leap from barrelless mice to humans is a giant one, Dr. Neumann says it is realistic. "These results go a long way to help our understanding of things like mental retardation in humans," he says.

Right now, the implications of these findings are theoretical. One example Dr. Neumann gives for its applications is the possibility for preventing a gene mutation, such as a mutation causing dyslexia, from ever taking effect. He says the next step is to explore ideas such as this one.

The Medical Research Council of Canada (MRC) funded the study that yielded these results. However Dr. Neumann's proposal for renewal funding was denied by the MRC last year.

Dr. Neumann has been recognized internationally for his research on barrelless mice with the 1998 Pfizer Prize for Neuroscience and Diseases of the Nervous System. The results of this study were published in the July issue of Nature Genetics.