Of Mice, Men and Malleable Minds

Researchers say they have located the neurobiological basis of rodent and human individuality

Does the adult brain continue to grow in accordance with the challenges it faces? Why do identical twins who share their genes and environment grow up into such different individuals? A new study published in Science and conducted by scientists from various disciplines—neuroscientists, ethologists, computer scientists and developmental psychologists—shows that individual experiences influence the development of new neurons, leading to measurable changes in the brain.

Forty genetically identical mice were selected for the study. They were all made to live in a similar environment (an enclosure), but each of them was offered a variety of activity and exploration options. To track each mouse’s movement and exploratory behaviour, they were equipped with a micro-chip.

Despite identical genes and a common environment, the study found that the mice showed highly individualised behavioural patterns. These differences increased over the three-month project. Further, these differences were associated with differences in the generation of new neurons in the hippocampus region of the brain, which is associated with learning and memory. The animals that explored the environment to a greater degree grew more new neurons than those that were relatively passive.

The researchers claim that the findings of this study can be applied to humans as well. It is known that new neurons are generated in the hippocampus region of the human brain so as to react to new information flexibly. According to the researchers, they have thus been able to locate the neurobiological basis of individuality in humans. Professor Ulman Lindenberger, director of the Center for Lifespan Psychology at the Max Planck Institute for Human Development (MPIB) in Berlin, who was one of the researchers, says, “Our findings show that development itself contributes to differences in adult behaviour. This is what many have assumed, but now there is direct neurobiological evidence in support of this claim. Our results suggest that experience influences the ageing of the human mind.”

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