New research refutes the age-old myth that the loss of one sense may sharpen other senses. A new study from the University of Montreal found that blind people have no keener sense of smell than the sighted. Vision loss simply makes blind people pay more attention to how they perceive smells, the researchers said.
"If you enter a room in which coffee is brewing, you will quickly look for the coffee machine. The blind person entering the same room will only have the smell of coffee as information," said graduate reseacher Mathilde Beaulieu-Lefebvre. "That smell will therefore become very important for their spatial representation."
The study involved 25 subjects, 11 of whom had been blind since birth. Participants answered a questionnaire and then participated in two experiments. In the first, they tired to distinguish between 16 different perfumes. In the second, they lay in a machine called a tomodensitometer and tried to identify three smells: a rose, vanilla and butanol (a sweet alcohol).
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"There is an urban legend that blind people have better smell than the sighted. We are proving this to be false," said Maurice Ptito, a professor at the University of Montreal and Beaulieu-Lefebvre's thesis director. "However, the blind do set themselves apart when it comes to cognitive efforts."
Using functional imagery, the researchers determined that the blind use a region of the brain called the secondary olfactory cortex more than the sighted when they smell. They also use the occipital cortex, which is normally used for vision .
"That's interesting because it means the blind are recuperating that part of their brain," said Ptito. "We're not speaking of recycling per se, yet that part of the brain is reorganized and used otherwise."
The loss of vision may affect each of the other senses differently. A 1998 Vanderbilt University study found that children with visual disabilities were somewhat better than sighted children at determining what direction a sound was coming from.
The research on the sense of smell could lead to concrete applications that may help blind people navigate in their surroundings.
"For instance, smells are very peculiar in shopping centers," said Beaulieu-Lefebvre. "A hair salon, a pharmacy and a clothing store each have their own distinctive scent. We could easily foresee developing re-adaptation programs for getting around in such places."
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