A research team led by Professor Franco Lepore, director of the Centre for Research in Neuropsychology and Cognition at the Université de Montréal, has shown that both early-and late-onset blind people have better sound discrimination abilities than people with normal vision.
Reported in the latest edition of the journal Current Biology, the study demonstrates for the first time that blind people from both groups perform equally well in tests requiring them to map auditory space beyond their peri-personal environment. These results led the researchers to conclude that neural structures can be reorganized even after the first few years of life.
Until now, similar studies have mainly focused on hearing in near space that can be calibrated by touch or, for example, with a cane. For this particular study, Professor Lepore and his team subjected three groups of ten people each (early- and late-onset blind subjects and a control group of blindfolded, sighted subjects) to spatial hearing tests in which each subject had to locate sounds from three meters away and distinguish them from other ambient noise. The early- and late-onset blind participants were far more successful than the control group at both tasks.
"Humans are remarkably adaptable. We can't quite explain these results," said Professor Lepore. "Of course, hearing is far more important to blind people so it's possible that they spend proportionately more time developing this sense. It's also possible that their superior performance reflects cross-modal cortical reorganization."
Professor Lepore's research team has long been interested in cross-modal cortical reorganization and the use of different sensory systems to compensate for losses. Back in 1998, Nature published the team's study on near-space auditory mapping by blind people. Earlier this year, this same journal published another study by this group on superior tone discrimination abilities in the blind.
The study published today is the first to show that early- and late-onset blind people performed at similar levels and better than sighted people. New studies are underway that will evaluate the response of deaf people to visual stimuli and the ability of blind people to navigate in a maze.