Study: Experience Builds Neural Connections, Differentiates Twins
May 10, 2013

Study: Experience Builds Neural Connections, Differentiates Twins

Brett Smith for — Your Universe Online

From Mary-Kate and Ashley Olsen to professional hockey players Henrik and Daniel Sedin, identical twins have always captivated the public´s imagination. Although they are genetically identical, anyone who has gotten to know a pair of twins can begin to pick up on the subtle differences that make each person unique.

Based on research involving mice twins, a group of German researchers has found an individual´s personal experiences add to the neural connections within the brain, allowing that individual to deviate in its own unique way, according to a new study in the journal Science.

To reach this conclusion, the team housed 40 genetically identical mice twins in an intricate, five-level cage — complete with glass chutes, toys, scaffolds, nesting places and other features. The mice were able to explore about five square yards of space.

“The animals were not only genetically identical, they were also living in the same environment,” Gerd Kempermann, the principal researcher and a professor of genomics regeneration at the German Center for Neurodegenerative Disease in Dresden, said in a statement. “However, this environment was so rich that each mouse gathered its own individual experiences in it. Over time, the animals therefore increasingly differed in their realm of experience and behavior.”

The mice were also fitted with a microchip that sent out electromagnetic signals, allowing the scientists to track the mice as they moved and to record their brain activity. While some mice roamed throughout the entire enclosure, some stayed close to familiar paths and areas. Over the course of three months, the team also observed the mice developing their own unique personality.

"Over time, the animals therefore increasingly differed in their realm of experience and behavior," Kempermann told the AFP.

The team found the most explorative mice were generating more new neurons in the hippocampus, the brain region for learning and memory, than their more passive counterparts.

In their report, the researchers said they have demonstrated how personal experiences and learned behavior contribute to individualization, asserting that neither genetics nor environment is responsible for this growth.

“Adult neurogenesis also occurs in the hippocampus of humans,” Kempermann said. “Hence, we assume that we have tracked down a neurological foundation for individuality that also applies to humans.”

The findings give new clues to how the brain works, and could have implications for future research on learning and aging, the researchers said.

"When viewed from educational and psychological perspectives, the results of our experiment suggest that an enriched environment fosters the development of individuality," co-author Ulman Lindenberger, director of the Center for Lifespan Psychology at the Max Planck Institute for Human Development, told the AFP.

In the journal, the study was accompanied by a commentary written by Olaf Bergmann and Jonas Frisen of the Karolinska Institute in Stockholm, Sweden, who were not directly involved in the research. They said the study has two main uses.

"Molecular understanding of neurogenesis will hopefully aid in the rational development of new classes of drugs for psychiatric disease," they wrote, adding that it "may teach us... how living our lives makes us who we are."