Experience key to individuality

Experience leads to the growth of new brain cells, giving rise to a person's individuality, a new study has found.
Researchers from the DFG-Center for Regenerative Therapies Dresden - Cluster of Excellence at the TU Dresden (CRTD), the Dresden site of the German Center for Neurodegenerative Diseases (DZNE), and the Max Planck Institute for Human Development in Berlin took part in the study.
The adult brain continues to grow with the challenges that it faces; its changes are linked to the development of personality and behaviour.
Scientists set out to determine the link between individual experience and brain structure.
They observed forty genetically identical mice that were kept in an enclosure offering a large variety of activity and exploration options.

"The animals were not only genetically identical, they were also living in the same environment," explains principal investigator Gerd Kempermann, Professor for Genomics of Regeneration, CRTD, and Site Speaker of the DZNE in Dresden.

"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," Kempermann said.
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.
Despite a common environment and identical genes the mice showed highly individualised 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," said Kempermann.
"Animals that explored the environment to a greater degree also grew more new neurons than animals that were more passive," Kempermann said.
The authors found that personal experiences and ensuing behaviour contribute to the individualisation of the brain.
"Adult neurogenesis also occurs in the hippocampus of humans. Hence we assume that we have tracked down a neurobiological foundation for individuality that also applies to humans," Kempermann said.