Numerical thinking in humans relies on a neural network involving a brain region called the intraparietal sulcus (IPS). However, how experience affects the development of this neural network remains unclear.

Researchers explored how visual experience affects the development of the numerical reasoning network by comparing neural responses to number in congenitally blind and sighted individuals. Seventeen congenitally blind and 19 sighted adults performed a math task and a sentence comprehension task while undergoing fMRI.

In both groups, the IPS exhibited greater activation during the math task than during the language task. A part of the visual cortex, the right middle occipital gyrus (rMOG), also exhibited greater activation during the math task than during the language task in blind individuals, but not in sighted individuals. The degree of rMOG activation in blind individuals was sensitive to the degree of mathematical difficulty.

The results suggest that the role of the IPS in number processing develops independently of visual experience. However, in the absence of visual experience, parts of the visual cortex are co-opted for number processing, indicating neural plasticity early in development, according to the authors.

http://www.pnas.org/content/early/2016/09/14/1524982113