The mechanisms underlying normal spike activity of the primary afferent synapse in the cochlea and its dysfunction: an investigation of the possible mechanisms of peripheral tinnitus and auditory neuropathy

Catherine McMahon

Research output: ThesisDoctoral Thesis

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Abstract

[Truncated abstract] One of the problems in researching tinnitus is that it has often been assumed that the physiological mechanisms underlying the tinnitus percept cannot be objectively measured. Nonetheless, it is generally accepted that the percept results from altered spontaneous neural activity at some site along the auditory pathway, although it is still debated whether it is produced by: synchronisation of activity of adjacent neurones; a change in the temporal pattern of activity of individual neurones; or an increase in the spontaneous firing rate per se. Similarly, it is possible that the recently coined “auditory neuropathy” is produced by under-firing of the primary afferent synapse, although several other mechanisms can also produce the symptoms described by this disorder (normal cochlear mechanical function but absent, or abnormal, synchronous neural firing arising from the cochlea and auditory brainstem, known as the auditory brainstem response, or ABR). Despite an absent ABR, some subjects can detect pure tones at near-normal levels, although their ability to integrate complex sounds, such as speech, is severely degraded in comparison with the pure-tone audiogram. The aim of the following study was to investigate the normal mechanisms underlying neural firing at the primary afferent synapse, and its regulation, to determine the possible mechanisms underlying over-firing (tinnitus) or under-firing (auditory neuropathy) of primary afferent neurones.
Original languageEnglish
QualificationDoctor of Philosophy
Publication statusUnpublished - 2004

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