The effect of binocular and monocular viewing on sound localization
Adria E. N. Hoover, Laurence R. Harris, Jennifer K. E. Steeves
Poster
Time: 2009-07-02 09:00 AM – 10:30 AM
Last modified: 2009-06-04
Abstract
PROBLEM
Does temporary loss of binocularity and asymmetrical cortical input in normally sighted individuals have immediate effects on audition? Research suggests that early-blind individuals can localize sound better than sighted controls (Lessard et al., 1998 Nature 395: 278). This may reflect recruiting of visual cortex for spatial auditory processing (Voss et al. 2008 Neuroimage 40: 746). Losing one eye deprives the contralateral hemisphere of crossed visual input and the ipsilateral cortex of uncrossed input and also eliminates binocular input. As a first step to investigating the possible consequences of this loss of binocularity and remaining asymmetrical cortical input on spatial auditory perception we measured the effect of covering one or both eyes in normally sighted individuals on sound localization.
METHODS
Subjects were asked to judge the location of double bursts (each one 30ms) of white noise played through tweeters spaced horizontally in a semicircular array in front of the subject. The speakers were hidden from view by a sound-transparent cloth. Subjects listened with (1) both eyes open in the light, viewing a fixation point straight ahead, (2) with either eye patched while viewing the fixation point and (3) with both eyes closed or in the dark. Subjects reported the perceived location of the sound relative to a visual scale. Each speaker location was tested several times. Conditions were run successively in counterbalanced order.
RESULTS
The perceived location of sounds with eyes closed was biased toward the straight ahead direction by an amount proportional to the speaker’s eccentricity. This bias increased when the eyes were open. When viewing monocularly, the bias toward straight ahead was even larger but only in the occluded field.
DISCUSSION
Changes in visual input have immediate effects on the accuracy with which sounds can be localized. Paradoxically vision does not help but rather increases error. Monocular viewing is associated with the greatest bias toward the straight ahead but only within the occluded field. This finding is discussed in terms of cortical contributions to sound localization and the possible effects of losing one eye.
ACKNOWLEDGEMENT
LRH and JKES are sponsored by NSERC; AENH has a NSERC PGS-M.
Does temporary loss of binocularity and asymmetrical cortical input in normally sighted individuals have immediate effects on audition? Research suggests that early-blind individuals can localize sound better than sighted controls (Lessard et al., 1998 Nature 395: 278). This may reflect recruiting of visual cortex for spatial auditory processing (Voss et al. 2008 Neuroimage 40: 746). Losing one eye deprives the contralateral hemisphere of crossed visual input and the ipsilateral cortex of uncrossed input and also eliminates binocular input. As a first step to investigating the possible consequences of this loss of binocularity and remaining asymmetrical cortical input on spatial auditory perception we measured the effect of covering one or both eyes in normally sighted individuals on sound localization.
METHODS
Subjects were asked to judge the location of double bursts (each one 30ms) of white noise played through tweeters spaced horizontally in a semicircular array in front of the subject. The speakers were hidden from view by a sound-transparent cloth. Subjects listened with (1) both eyes open in the light, viewing a fixation point straight ahead, (2) with either eye patched while viewing the fixation point and (3) with both eyes closed or in the dark. Subjects reported the perceived location of the sound relative to a visual scale. Each speaker location was tested several times. Conditions were run successively in counterbalanced order.
RESULTS
The perceived location of sounds with eyes closed was biased toward the straight ahead direction by an amount proportional to the speaker’s eccentricity. This bias increased when the eyes were open. When viewing monocularly, the bias toward straight ahead was even larger but only in the occluded field.
DISCUSSION
Changes in visual input have immediate effects on the accuracy with which sounds can be localized. Paradoxically vision does not help but rather increases error. Monocular viewing is associated with the greatest bias toward the straight ahead but only within the occluded field. This finding is discussed in terms of cortical contributions to sound localization and the possible effects of losing one eye.
ACKNOWLEDGEMENT
LRH and JKES are sponsored by NSERC; AENH has a NSERC PGS-M.