EAR ADVANTAGE IN DICHOTIC-LISTENING AFTER CORRECTION FOR EARLY CONGENITAL HEARING-LOSS

Twelve patients who had undergone surgical correction for either unila teral or bilateral congenital hearing loss were given a postoperative dichotic listening test for consonant-vowel-consonant (CVC) words. Fou r normal hearing control subjects were also tested. Patients were firs t given a test of subjective loudness, and the level of presentation o f stimuli in the atretic ear was adjusted accordingly. In the dichotic condition all controls exhibited a right ear advantage, and all unila teral atresia patients showed an ear advantage favouring the non-atret ic ear. Patients with bilateral atresia essentially exhibited no ear a dvantage. Patients had the same error rate as controls in the dichotic condition, which suggests that ear advantage was not due to increased errors in the atretic ear. For patients there was a significant relat ionship between ear advantage and both preoperative interaural asymmet ry in hearing loss and age at operation. Results suggest that a sensit ive and critical period for development of the ear is complete by 5 ye ars of age. Results also suggest some limited ability to adjust to per manent change in stimulation levels until, but not after, puberty. (C) 1998 Elsevier Science Ltd. All rights reserved.