Individual differences in suprathreshold hearing and relationship to cochlear synaptopathy

Threshold audiometry, although the foundation of current clinical hearing evaluations, provides limited information about suprathreshold hearing. Over the last few years, we have documented that even among listeners with normal thresholds and no hearing complaints, large individual differences exist in the ability to perceive subtle temporal features of clearly audible sounds, and to selectively process target speech in the presence of competing sounds. Furthermore, we find that these suprathreshold perceptual differences correlate with suprathreshold physiological measures from the brainstem and auditory nerve suggesting that perceptually-relevant differences may be present early along the auditory pathway. As a candidate mechanism explaining these observations, animal studies of acoustic overexposure and aging have robustly demonstrated that the afferent synapses and nerve terminals innervating the cochlea are especially vulnerable to damage. Interestingly, even a significant loss of cochlear synapses (...