Enhanced loudness perception in ears with reduced peripheral function: A remote psychoacoustic investigation

Abstract

Central gain models of hyperacusis propose that a loss of afferent input drives over-amplification of sound-evoked activity in the central auditory system, leading to enhanced loudness perception. We conducted a remote study aimed at quantifying variation in loudness perception as a function of peripheral auditory status [i.e., summating potential (SP)/action potential (AP) ratio]. To control for the contributions of age and other individual differences, twelve adults with normal hearing and strongly asymmetric SP/AP ratios between ears were recruited from a prior study. Participants completed a battery of self-directed psychoacoustic tests at home using calibrated headphones and tablet computers running custom software. Loudness perception was assessed at a variety of frequencies in each ear using standard clinical assessments [e.g., loudness discomfort levels (LDLs), dynamic range] and more fine-grained assessments of loudness growth as a function of stimulus intensity. While traditional measures of LDL and dynamic range varied widely both within and between subjects, ears with evidence of possible cochlear synaptopathy (high SP/AP ratios) demonstrated elevated loudness perception for intensities in-between threshold and LDL. Detailed assessments of loudness growth across sensation levels may be more sensitive to variation in underlying peripheral neural status than traditional, single-point clinical measures of loudness discomfort.