It is easier to rewire the brain in the early stages of life, however, in the later stages; it is difficult, but not impossible, says a new study.
The paper from MIT neuroscientists, in collaboration with Alvaro Pascual-Leone at Beth Israel Deaconess Medical Centre, has shed light on how the brain wires itself during the first few years of life, and could help scientists understand how to optimise the brain's ability to be rewired later in life.
Researchers have suggested that a small part of the brain's visual cortex that processes motion became reorganized only in the brains of subjects who had been born blind, not those who became blind later in life.
In the 1950s and '60s, scientists began to think that certain brain functions develop normally only if an individual is exposed to relevant information, such as language or visual information, within a specific time period early in life.
After that, they theorized, the brain loses the ability to change in response to new input.
Animal studies supported this theory. However, there have been indications in recent years that there is more wiggle room than previously thought, said Marina Bedny, lead author of the paper.
Bedny and colleagues wanted to determine if a part of the brain known as the middle temporal complex (MT/MST) could be rewired at any time or only early in life.
In the few rare cases where patients have lost MT function in both hemispheres of the brain, they were unable to sense motion in a visual scene.
Previous studies have shown that in blind people, MT is taken over by sound processing, but those studies didn't distinguish between people who became blind early and late in life.
In the new MIT study, the researchers studied three groups of subjects - sighted, congenitally blind, and those who became blind later in life (age nine or older). Using functional magnetic resonance imaging (fMRI), they tested whether MT in these subjects responded to moving sounds - for example, approaching footsteps.
MT reacted to moving sounds in congenitally blind people, but not in sighted people or people who became blind at a later age.
This suggests that in late-blind individuals, the visual input they received in early years allowed the MT complex to develop its typical visual function, and it couldn't be remade to process sound after the person lost sight. Congenitally blind people never received any visual input, so the region was taken over by auditory input after birth.
"We need to think of early life as a window of opportunity to shape how the brain works. That's not to say that later experience can't alter things, but it's easier to get organized early on," said Bedny.
Bedny believes that by better understanding how the brain is wired early in life, scientists may be able to learn how to rewire it later in life.
The new findings were published in the journal Current Biology.