Summary

Several studies have already demonstrated that patients with steeply sloping hearing loss of cochlear origin exhibit an improvement in frequency discrimination performance at or around the cut-off frequency. This enhancement cannot be explained in terms of peripheral mechanisms and should rather be interpreted in terms of central reorganization: i.e., injury-induced cortical plasticity. However, the reversibility and time course of such reorganization has not yet been described. Would reintroducing auditory stimuli alter this hearing loss-induced plasticity? The main goal of the present study was therefore to investigate the occurrence of secondary plasticity associated with hearing-aid fitting in human subjects. 9 subjects with steeply sloping hearing loss and who were candidates for auditory rehabilitation were tested. Discrimination-limen-for-frequency (DLF) enhancement was investigated at the frequency with the best DLF of each individual subject (bDLF) before and during auditory rehabilitation (at 1 month, 3 months and 6 months). From one month on, frequency discrimination performance decreased significantly at the bDLF frequency, while remaining stable at other frequencies. This normalization may reflect a new central reorganization reversing the initial injury-induced changes in the cortical map.