Visually impaired people appear to be fearless, navigating busy sidewalks and crosswalks, safely finding their way using nothing more than a cane as a guide.

The reason they can do this, researchers suggest, is that in at least some circumstances, blindness can heighten other senses, helping individuals adapt.

Reporting in the January issue of the journal NeuroImage (currently online), Natasha Leporé, a postgraduate researcher at UCLA's Laboratory of Neuro Imaging, and colleagues found that visual regions of the brain were smaller in volume in blind individuals than in sighted ones.

However, for non-visual areas, the trend was reversed - they grew larger in the blind. This, the researchers say, suggests that the brains of blind individuals are compensating for the reduced volume in areas normally devoted to vision.

"This study shows the exceptional plasticity of the brain and its ability to reorganize itself after a major input - in this case, vision - is lost," said Leporé. "In other words, it appears the brain will attempt to compensate for the fact that a person can no longer see, and this is particularly true for those who are blind since early infancy, a developmental period in which the brain is much more plastic and modifiable than it is in adulthood."

Researchers used an extremely sensitive type of brain imaging called tensor-based morphometry, which can detect very subtle changes in brain volume, to examine the brains of three different groups: those who lost their sight before the age of 5; those who lost their sight after 14; and a control group of sighted individuals. Comparing the two groups of blind individuals, the researchers found that loss and gain of brain matter depended heavily on when the blindness occurred.

Only the early-blind group differed significantly from the control group in an area of the brain's corpus callosum that aids in the transmission of visual information between the two hemispheres of the brain.

Source: University of California