They said understanding how brain structures are formed during normal brain development is the critical first step towards being able to sort out the nature of problems in various brain disorders. The study has been reported in Nature Neuroscience’s advance online publication Sunday.
“We have discovered how two completely different, ancient systems of brain circuits are formed, one that processes reproductive behaviour, and the other defensive/aggressive behaviour. We have discovered different sources of neurons belonging to each system,” said Prof Shubha Tole, TIFR scientist and principal investigator in the group.
“Our finding also provides an explanation for why these two groups of behaviours, both very ancient in evolution, are handled by separate pathways in the brain,” she said.
Brain circuit formation or malformation controls human behaviour, sensation, perception and emotion. According to experts, new discoveries in how particular circuits are formed and how they evolved can provide a framework to understand what happens when things go wrong with their function.
Tole said schizophrenia is thought to occur due to something going wrong during the development of the brain. “Another example is cerebral palsy, which is a result of problems with development of the cerebral cortex, such as the neurons don’t migrate properly,” Tole said.
“Our study uncovers an unexpected source and a new migration route for neurons (building blocks of the nervous system) that determines defensive/aggressive behaviours,” Tole said. “This finding will provide the framework for understanding why, for example, a particular disorder might affect defensive behaviour but not reproductive behaviour.”
The study, which was initiated in 2004 following a key finding in Prof Tole’s laboratory at TIFR , is the central PhD thesis work of her student Dhananjay Huilgol, who performed the bulk of the work in the paper, with help from students Bhaskar Saha and Achira Roy.
“We pursued not only the developmental angles but also the evolutionary angle of this study. It turns out that the migration route we discovered was laid out early in evolution, since it exists even in the frog, so the common ancestor of frogs, reptiles and mammals must have had this migration route too,” Tole said.
She said valuable contributions were made by Prof Susan Udin of the State University of New York (Buffalo, US) and Prof Tomomi Shimogori from RIKEN, Japan, and added it is significant that international collaborators are excited to contribute to projects such as this.