Quantifying supra-threshold sensory deficits in listeners with normal hearing thresholds

Abstract

There is growing suspicion that some listeners with normal-hearing thresholds may be suffering from a specific form of sensory deficit—a loss of afferent auditory nerve fibers. We believe such deficits manifest behaviorally in conditions where perception depends upon precise spectro-temporal coding of supra-threshold sound. In our lab, we find striking inter-subject differences in perceptual ability even among listeners with normal hearing thresholds who have no complaints of hearing difficulty and have never sought clinical intervention. Among such ordinary listeners, those who perform relatively poorly on selective attention tasks (requiring the listener to focus on one sound stream presented amidst competing sound streams) also exhibit relatively weak temporal coding in subcortical responses and have poor thresholds for detecting fine temporal cues in supra-threshold sound. Here, we review the evidence for supra-threshold hearing deficits and describe measures that reveal this sensory loss. Given our findings in ordinary adult listeners, it stands to reason that at least a portion of the listeners who are diagnosed with central auditory processing dysfunction may suffer from similar sensory deficits, explaining why they have trouble communicating in many everyday social settings.