Simon Landry
Marie-Soleil Houde
Marianne Belanger
Douglas M. Shiller
Ecole d'orthophonie et d'audiologie
Universite de Montreal
Montreal, Quebec, Canada
Francois Champoux, Ph.D. - francois.champoux@umontreal.ca
Laboratoire de recherche en neurosciences auditives
Ecole d'orthophonie et d'audiologie
Universite de Montreal
Montreal, Quebec, Canada
Website : http://www.neuroaudiolab.com
Popular version of paper 5aPP10
Presented Friday morning, May 18, 2012
163rd ASA Meeting, Hong Kong
It is a commonly held belief that blind individuals have enhanced auditory and tactile sensory abilities; yet, there is a surprising lack of scientific evidence to support these claims. In terms of audition, studies have shown blind subjects to be better than sighted subjects at localizing sound and a single study suggested that blindness might improve the capacity to discriminate between sound frequencies. The supposed enhanced tactile abilities have been studied at a greater degree and can surprisingly be seen as early as days or even minutes following blindness. This rapid change for auditory ability has not yet been clearly demonstrated.
Two questions remain surrounding blindness and enhanced abilities. Can blindness improve more complex auditory abilities and if so, can these changes be triggered after only a few minutes of visual deprivation, as seen with tactile abilities? Here, we present data demonstrating that a very short period of visual deprivation can enhance harmonicity, a primary auditory cue that plays a key role in both music and speech perception.
When we speak or when we play a musical instrument, the sound produced by our mouth or instrument has specific harmonic relations. That is to say that if we play a certain note on a piano, that note has many related "layers". However, we do not hear all these "layers" since our brain simply associates them all together and we only hear the lowest one. It is through this complex computation based on specific components of the sound that our brain can interpret and distinguish auditory signals coming from different people or different instruments. The capacity to identify the harmonic relation between sounds (or harmonicity) has been determined to be one of the most powerful factors when we interpret our auditory surroundings.
Harmonicity can easily be evaluated using a simple discrimination task in which similar harmonic "layers" are set up and one of them is gradually modified until the individual notices two "layers" instead of one. In our study, healthy seeing individuals completed such a discrimination task while blindfolded. The discrimination task was administered twice, separated by a 90-minute interval during which the participants conversed with the experimenter in a quiet room. Half of the participants kept the blindfold on during the interval period, depriving them of all visual input, while the other half had their blindfold removed.
Unsurprisingly, no significant difference was found between the two groups in their ability to discriminate harmonicity prior to visual deprivation. However, results in the testing session following visual deprivation revealed that visually deprived individuals were significantly better in their discrimination ability compared to the non-visually-deprived group.
Regardless of the neural basis for such an enhancement, our results suggest that the potential for change in auditory perception is much greater than previously assumed.