Abstract
Introduction: The quality of early visual experience is known to influence the development of sound localization ability. Sound localization is normal or enhanced in humans with early complete vision loss in one or both eyes, but diminished in those with selective loss of central vision bilaterally. In this study, we investigate sound localization ability in humans with amblyopia, a unilateral visual impairment caused by anomalous visual experience (i.e. strabismus and/or anisometropia) in early life. Methods: In Experiment 1, amblyopic (n = 14) and visually normal (n = 16) participants judged whether the second click of a pair was located to the left or right of the first. One click of each pair always occurred at the central reference position. Click position was controlled by amplitude panning between stereo speakers. Clicks were presented in darkness at 11 evenly-spaced virtual positions along the central 30 degrees of azimuth. Experiment 2 replicated Experiment 1 with amblyopic (n = 10, 5 new) and visually normal (n = 12, 8 new) participants using a horizontal array of 11 speakers. All participants passed an audiometer-based hearing screen. Just noticeable differences (JND) for auditory spatial resolution were derived from individual psychometric functions, and group differences were tested using the Mann-Whitney U test. Results: In experiment 1, the median JND for normal participants was 3.2 degrees, compared to 4.0 degrees in the amblyopia group (p = 0.028). In experiment 2, the same pattern was found, with the median JND in the normal group being 2.1 degrees compared to 3.7 degrees in the amblyopia group (p = 0.035). Conclusion: Horizontal auditory spatial resolution is diminished among people with unilateral amblyopia. The spatial uncertainty of amblyopic vision may disrupt the developmental calibration of the auditory spatial map.
Meeting abstract presented at VSS 2017