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Brain 'pruning' causes girls to mature faster than boys

Press Trust of India  |  London 

Girls mature faster than boys during their teenage years because their brains start re-organising connections early - a process that improves the organ's function.

As we grow older, our brains undergo a major reorganisation reducing the connections in the brain.

Scientists led by Dr Marcus Kaiser and Sol Lim at Newcastle University studied people up to the age of 40, and found that while overall connections in the brain get streamlined, long-distance connections that are crucial for integrating information are preserved.

The researchers suspect this newly discovered selective process might explain why brain function does not deteriorate - and indeed improves - during this pruning of the network.

They also found that these changes occurred earlier in females than in males.

"Long-distance connections are difficult to establish and maintain but are crucial for fast and efficient processing," Kaiser said.

"If you think about a social network, nearby friends might give you very similar information - you might hear the same from different people. People from different cities or countries are more likely to give you novel information.

"In the same way, some information flow within a brain module might be redundant whereas information from other modules, say integrating the optical information about a face with the acoustic information of a voice is vital in making sense of the outside world," Kaiser said.

The researchers at Newcastle, Glasgow and Seoul universities evaluated the scans of 121 healthy participants between the ages of 4 and 40 years as this is where the major connectivity changes can be seen during this period of maturation and improvement in the brain.

Using a non-invasive technique called diffusion tensor imaging - a special measurement protocol for Magnetic Resonance Imaging (MRI) scanners - they demonstrated that fibres are overall getting pruned that period.

They found not all projections (long-range connections) between brain regions are affected to the same extent; changes were influenced depending on the types of connections.

Projections that are preserved were short-cuts that quickly link different processing modules, eg for vision and sound, and allow fast information transfer and synchronous processing.

The team showed for the first time that loss of white matter fibres between brain regions is a highly selective process - a phenomenon called preferential detachment.

They show that connections between distant brain regions, between brain hemispheres, and between processing modules lose fewer nerve fibers during brain maturation than expected.

The researchers said this may explain how we retain a stable brain network during brain maturation.

"The loss of connectivity during brain development can actually help to improve brain function by reorganising the network more efficiently," Lim said.

The study appears in journal Cerebral Cortex.

First Published: Fri, December 20 2013. 15:41 IST