Blind people use brain's vision centre to solve math

People born without sight appear to solve math problems using visual areas of the brain, researchers including one of Indian origin have found.

Human babies and even animals have a basic number sense that many believe evolves from seeing the world and trying to quantify all the sights but vision has nothing to do with it.

Neuroscientists at Johns Hopkins University (JHU) in the US have found that the brain network behind numerical reasoning is identical in blind and sighted people.

The researchers also found the visual cortex in blind people is highly involved in doing math, suggesting the brain is vastly more adaptable than previously believed.

"The number network develops totally independently of visual experience," said lead author Shipra Kanjlia, a graduate student in JHU's Department of Psychological and Brain Sciences.

"These blind people have never seen anything in their lives, but they have the same number network as people who can see," said Kanjlia.

The researchers had congenitally blind people and sighted people wearing blindfolds solve math equations and answer language questions while having a brain scan.

With the math problems, participants heard pairs of increasingly complicated recorded equations and responded if the value for "x" was the same or different.

The participants also heard pairs of sentences and responded if the meaning of the sentences was the same or different.

With both blind and sighted participants, the key brain network involved in numerical reasoning, the intraparietal sulcus, responded robustly as participants considered the math problems.

Meanwhile, in blind participants only, regions of the visual cortex also responded as they did math. The visual cortex did not merely respond - the more complicated the math, the greater the activity in the vision centre.

It had been thought that brain regions including the visual cortex had entrenched functions that could change slightly but not fundamentally, researchers said.

The new findings underscore recent research that showed just the opposite: The visual cortex is extremely plastic and, when it is not processing sight, can respond to everything from spoken language to math problems.

The findings, taken together with earlier results, suggest the brain as a whole could be extremely adaptable, almost like a computer that - depending on data coming in - could reconfigure to handle almost limitless types of tasks.

It could someday be possible to reroute functions from a damaged area to a new spot in the brain, said co-author Marina Bedny, an assistant professor of psychological and brain sciences.

"If we can make the visual cortex do math, in principle we can make any part of the brain do anything," Bedny said.

The finding was published in the journal Proceedings of the National Academy of Sciences.