Enhanced Central Neural Gain Compensates Acoustic Trauma-induced Cochlear Impairment, but Unlikely Correlates with Tinnitus and Hyperacusis. (21st May 2019)

• Record Type: Journal Article
• Authors: Möhrle, Dorit; Hofmeier, Benedikt; Amend, Mario; Wolpert, Stephan; Ni, Kun; Bing, Dan; Klose, Uwe; Pichler, Bernd; Knipper, Marlies; Rüttiger, Lukas
• Is Part Of: Neuroscience. Volume 407(2019)
• Page Start: 146
• Page End: 169
• Publication Date: 2019-05-21
• Subjects: ABRs Auditory Brainstem Responses -- AC auditory cortex -- AF auditory fiber -- AM amplitude modulation -- ASRs acoustic startle responses -- BOLD blood-oxygen-level dependent -- CN cochlear nucleus -- CSF cerebrospinal fluid -- dB SL decibel sensation level -- dB SPL decibel sound pressure level -- DPOAE Distortion Product Otoacoustic Emission -- EFR envelope following response -- FDR False Discovery Rate -- FWHM full-width half-maximum -- I–O input–output -- IC inferior colliculus -- high SR high spontaneous rate -- HKI Hyperakusis Inventory Questionnaire -- low SR low spontaneous firing -- MOC medial olivocochlear system -- OHC outer hair cell -- rs-fMRI resting state functional Magnetic Resonance Imaging -- RF radio frequency -- RM repeated measures -- rms root mean square -- ROI region of interest -- SD standard deviation -- SEM standard error of the mean -- SOC superior olivary complex; hyperacusis -- tinnitus -- hidden hearing loss -- inner hair cell synaptopathy -- central compensation -- neural gain; Neurochemistry -- Periodicals; Neurophysiology -- Periodicals; Neurology -- Periodicals; Neurochimie -- Périodiques; Neurophysiologie -- Périodiques; Neurochemistry; Neurophysiology; Electronic journals; Periodicals; Electronic journals; 612.8
• DOI: 10.1016/j.neuroscience.2018.12.038
• Languages: English
• ISSNs: 0306-4522

Abstract

Highlights: Equally noise-exposed rats can be behaviorally divided into groups with tinnitus or hyperacusis. Groups with tinnitus or hyperacusis behavior do not differ in hearing thresholds from symptom-free groups. Symptom-free groups show elevated central gain and shortened response latency to auditory stimuli. In contrast, the tinnitus group shows reduced central gain and delayed response latency to auditory stimuli. Humans and animals with tinnitus reveal reduced central responsiveness and reduced rs-fMRI activity in the auditory cortex. Abstract: For successful future therapeutic strategies for tinnitus and hyperacusis, a subcategorization of both conditions on the basis of differentiated neural correlates would be of invaluable advantage. In the present study, we used our refined operant conditioning animal model to divide equally noise-exposed rats into groups with either tinnitus or hyperacusis, with neither condition, or with both conditions co-occurring simultaneously. Using click stimulus and noise burst-evoked Auditory Brainstem Responses (ABR) and Distortion Product Otoacoustic Emissions, no hearing threshold difference was observed between any of the groups. However, animals with neither tinnitus nor hyperacusis responded to noise trauma with shortened ABR wave I and IV latencies and elevated central neuronal gain (increased ABR wave IV/I amplitude ratio), which was previously assumed in most of the literature to be a neural correlate for tinnitus. In contrast, animals with tinnitus had reduced neural response gain and delayed ABR wave I and IV latencies, while animals with hyperacusis showed none of these changes. Preliminary studies, aimed at establishing comparable non-invasive objective tools for identifying tinnitus in humans and animals, confirmed reduced central gain and delayed response latency in human and animals. Moreover, the first ever resting state functional Magnetic Resonance Imaging (rs-fMRI) analyses comparing humans and rats with and without tinnitus showed reduced rs-fMRI activities in the auditory cortex in both patients and animals with tinnitus. These findings encourage further efforts to establish non-invasive diagnostic tools that can be used in humans and animals alike and give hope for differentiated classification of tinnitus and hyperacusis.