Figure 6.

Binaural hearing in children with a history of MED. Children aged 6–12 years, presenting at the Otolaryngology Department, Radcliffe Infirmary, Oxford, for tympanostomy surgery to relieve MED were paired, in 1989, with control children who had no known history of MED (from ref. 55). These two groups were examined for binaural unmasking—the difference in the detection threshold of a 500-Hz tone presented against a binaural noise stimulus when the tone is either in or out of phase between the two ears. This test is thought to provide a measure of the binaural contribution to the “cocktail party effect.” Children with a history of MED had impaired binaural hearing, even though their absolute thresholds were normal at the time of testing. These findings together suggest that a history of unilateral or asymmetric hearing loss can lead to impaired central auditory function. In 1996, 7 years later (from ref. 58), about two-thirds of the same children were re-examined. Both groups now had normal levels of binaural unmasking, suggesting that prolonged normal binaural experience can lead to the restoration of central auditory function.