ASA 127th Meeting M.I.T. 1994 June 6-10

3pPP16. Absence of ``amblyocusis'' after atypical binaural experience.

Lincoln Gray

Debra Wilmington

Robert Jahrsdoerfer

Dept. of Otolaryngol., Univ. Texas Med. School, Houston, TX 77030

Binaural hearing in patients after surgical correction of congenital conductive hearing losses suggests that ears do not respond like eyes to atypical early experience [D. Wilmington, L. Gray, and R. Jahrsdoerfer, Hear. Res. 74 (1/2) (1994)]. Data from patients with aural atresia, born with one normal ear and receiving a newly functional ear at various ages, are reviewed. All aspects of binaural processing improved after surgery, but horizontal localization did not improve as much as many discriminations. Unlike the visual system where asymmetric inputs must be corrected before about 8 years of age, the human auditory system is much more forgiving of early atypical experience. Even after years of asymmetric input, a corrected atretic ear has near-normal discriminations---as revealed by normal monaural audiometry, interaural time and intensity differences, and binaural unmasking of signals in noise. The phenomenon of amblyopia, or dull vision, does not occur in hearing. A speculative difference between hearing and vision is discussed: details are heard better than patterns after early auditory deprivation, and patterns are seen better than details after early visual deprivation.