Restoring an allocentric reference frame in blind individuals through echolocation

Abstract

Recent psychophysical studies have described task-specific auditory spatial deficits in congenitally blind individuals. We investigated auditory spatial perception in congenitally blind children and adults during different auditory spatial tasks that required the localization of brief auditory stimuli with respect to either external acoustic landmarks (allocentric reference frame) or their own body (egocentric reference frame). Early blind participants successfully represented sound locations with respect to their body. However, they showed relative poor precision when compared to sighted participants during the localization of sound with respect to external auditory landmarks, suggesting that vision is crucial for an allocentric representation of the auditory space. In a separate study, we tested three congenitally blind individuals who used echolocation as a navigational strategy, to assess the benefit of echolocation on auditory spatial perception. Blind echolocators did not show the same impairment in auditory spatial localization reported for blind non-echolocators, but rather proved enhanced precision and accuracy as compared to blind non-echolocators and sighted participants. Our results suggest that echolocation can compensate for the spatial deficit reported in early blind individuals, likely by reactivating an allocentric reference frame needed to shape spatial representations similar to those generated by vision.