- What is the link between individual experience and brain structure?
- Why do identical twins not resemble each other perfectly even when they grew up together?
To shed light on these questions, the scientists observed forty genetically identical mice that were kept in an enclosure offering a large variety of activity and exploration options.
"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 behaviour."
New neurons for individualized brains
Each of the mice was equipped with a special micro-chip emitting electromagnetic signals.
This allowed the scientists to construct the mice's movement profiles and to quantify their exploratory behaviour.
The result: Despite a common environment and identical genes the mice showed highly individualized behavioural patterns.
They reacted to their environment differently. In the course of the three-month experiment these differences increased in size.
"Though the animals shared the same life space, they increasingly differed in their activity levels. These differences were associated with differences in the generation of new neurons in the hippocampus, a region of the brain that supports learning and memory," says Kempermann.
"Animals that explored the environment to a greater degree also grew more new neurons than animals that were more passive."
"Hence, we assume that we have tracked down a neurobiological foundation for individuality that also applies to humans" says Kempermann.
"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 aging of the human mind."
- J. Freund, A. M. Brandmaier, L. Lewejohann, I. Kirste, M. Kritzler, A. Kruger, N. Sachser, U. Lindenberger, G. Kempermann. Emergence of Individuality in Genetically Identical Mice. Science, 2013; 340 (6133): 756 DOI:10.1126/science.1235294