Audiotactile integration is reduced in congenital blindness in a spatial ventriloquism task

In the ventriloquism effect, the presentation of spatially discrepant visual information biases the localization of simultaneously presented sounds. Recently, an analogous spatial influence of touch on audition has been observed. By manipulating hand posture, it has been demonstrated that this audiotactile ventriloquist effect predominantly operates in an external frame of reference. In the present study, we examined the contribution of developmental vision to audiotactile interactions as indicated by the ventriloquism effect. Congenitally blind, late blind and sighted adults were asked to report the perceived location of sounds presented from a left, a central or a right location. Auditory stimuli were either delivered alone or concurrently with touches at the left or the right hand. The hands were located to the right and to the left of the lateral speakers and participants either adopted an uncrossed or a crossed hand posture. While sighted controls and late blind participants similarly mislocalized auditory stimuli toward the concurrent tactile stimuli in bimodal trials, the congenitally blind showed a reduced ventriloquism effect. All groups showed a reduced audiotactile ventriloquism effect in the crossed hand condition. However, the magnitude of the reduction was significantly larger in the group of congenitally blind than in the group of sighted controls. These results suggest reduced audio-tactile interactions in spatial processing following a lack of visual input from birth.