title: Frequency selectivity of the human cochlea: Suppression tuning of spontaneous otoacoustic emissions.
abstract: Frequency selectivity is a key functional property of the inner ear and since hearing research began, the frequency resolution of the human ear has been a central question. In contrast to animal studies, which permit invasive recording of neural activity, human studies must rely on indirect methods to determine hearing selectivity. Psychophysical studies, which used masking of a tone by other sounds, indicate a modest frequency selectivity in humans. By contrast, estimates using the phase delays of stimulus-frequency otoacoustic emissions (SFOAE) predict a remarkably high selectivity, unique among mammals. An alternative measure of cochlear frequency selectivity are suppression tuning curves of spontaneous otoacoustic emissions (SOAE). Several animal studies show that these measures are in excellent agreement with neural frequency selectivity. Here we contribute a large data set from normal-hearing young humans on suppression tuning curves (STC) of spontaneous otoacoustic emissions (SOAE). The frequency selectivities of human STC measured near threshold levels agree with the earlier, much lower, psychophysical estimates. They differ, however, from the typical patterns seen in animal auditory nerve data in that the selectivity is remarkably independent of frequency. In addition, SOAE are suppressed by higher-level tones in narrow frequency bands clearly above the main suppression frequencies. These narrow suppression bands suggest interactions between the suppressor tone and a cochlear standing wave corresponding to the SOAE frequency being suppressed. The data show that the relationship between pre-neural mechanical processing in the cochlea and neural coding at the hair-cell/auditory nerve synapse needs to be reconsidered.
authors.affiliation: Cochlear and Auditory Brainstem Physiology, Department of Neuroscience, School of Medicine and Health Sciences, Cluster of Excellence "Hearing4all", Research Centre Neurosensory Science, Carl von Ossietzky University Oldenburg, 26129 Oldenburg, Germany.
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Manley
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Otorhinolaryngology/Head and Neck Surgery, P.O. Box 30.001, 9700 RB Groningen, The Netherlands; University of Groningen, Graduate School of Medical Sciences, Research School of Behavioural and Cognitive Neuroscience, The Netherlands. Electronic address: p.van.dijk@umcg.nl.
authors.forename: Pim
authors.initials: P
authors.lastname: van Dijk
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001309:Auditory Threshold / Q000502:physiology*; D003051:Cochlea / Q000502:physiology*; D003056:Cochlear Nerve / Q000473:pathology; D007758:Ear, Inner; D005260:Female; D006309:Hearing / Q000502:physiology*; D006801:Humans; D008297:Male; D009474:Neurons / Q000473:pathology; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology*; D013016:Sound; D055815:Young Adult
keywords: Frequency selectivity; Human hearing; Otoacoustic emissions