Have you ever heard that girls' brains mature sooner than boys' brains? Guess what — it's not a myth after all! Maturing brains selectively strip away some of the connections they don't need, while maintaining the parts that are crucial. Those crucial parts turn out to be long-distance connections in particular.
Though some connections are lost during this process, the selective reduction of connections does not decrease brain function. On fact, the streamlining process may be very important to the brain's functioning, a team from Newcastle University in Britain reveals. The team's insights into the brain's streamlining are fascinating. Dr Marcus Kaiser, reader in Neuroinformatics at Newcastle, participated in the study.
He says: "Long-distance connections are difficult to establish and maintain but are crucial for fast and efficient processing."
Why long-distance connections? Dr Kaiser compares them to social networks like Facebook to make this complex subject easier to understand for laypeople. Nearby friend will give you similar information, he says, while those who are further away are much more likely to surprise you with fresh and new insights. Your brain is similar, Dr Kaiser says: "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."
Brain Streamlining Highly Selective
To get their information, researchers from Newcastle, Glasgow and Seoul Universities looked at the brains of 121 healthy people aged between four and 40. That might seems like a huge age range, but brain streamlining happens exactly within that window of time. The participants' brains were scanned using a very sensitive form of MRI scanning known as DTI, diffusion tensor imaging. This method looks at water as it travels along nerve fibers.
The research team found that there is indeed some crucial "brain maintenance work" going on between the ages of four and 40, and also discovered that the trimming of long-distance connections (known as projections) was very selective indeed. Some types of connections were trimmed much more heavily than others.
Interestingly, there appeared to be some multi-sensory cooperation going on. The long-distance connections that got preferential treatment and were preserved were those that connected one processing module to another — something that allows information to be processed really quickly. Sound and vision modules were connected, for instance.
There were fewer brain connections between distant regions, between the hemispheres, and between processing modules than expected. But fewer connections in these places apparently means a mature, stable brain.
Now, back to what you really wanted to know. The pruning and trimming process that gives humans mature brains was found to begin at age 10 in girls. Boys had to wait a "little" longer — for them, the process did not begin until age 20. Girls really do mature earlier than boys, but boys do catch up.