Right ear advantage in cochlear implant simulation: short- and long-term effects

This study investigates the short-term effects of degraded auditory input on the right ear advantage (REA) and the REA following long-term exposure to vocoder-processed sounds, which simulate cochlear implant (CI) hearing. Vocoder processing allows normal hearing individuals to experience CI-like hearing conditions, enabling an exploration of how modifications to auditory input influence the REA.

A repeated-measures design was employed. Twenty-two normal-hearing participants completed dichotic word recognition tests under three auditory conditions: bilateral normal hearing, short-term vocoder-processed hearing, and long-term vocoder-processing hearing. REA was assessed after one month of training with vocoder-processed words to simulate long-term exposure.

The study included 22 normal-hearing participants aged 19-28 years. All participants had normal hearing and no history of auditory or neurological disorders.

REA significantly decreased under the short-term vocoder condition compared to the normal hearing condition (p < 0.001). However, after long-term training, REA significantly improved (p < 0.001), and this improvement approached normal hearing levels (p = 0.28).

Our findings suggest that short-term exposure to vocoder-processed auditory input disrupts the REA, but extended training can restore it. These results provide insights into cortical plasticity and its role in auditory adaptation, with potential implications for developing rehabilitation strategies for CI users.