Alexander Hardy
Postgraduate research project
Title: Neurophysiological and behavioural measures of hearing loss–related plasticity in the human central auditory system
Area: Auditory neuroscience
Methods: EEG, psychophysics.
Tinnitus, the perception of a phantom sound when no external sound is present, is a common phenomenon that many people have temporarily experienced. This often occurs after exposure to loud environments (for example music concerts). However in an estimated 10-15% of the population (Snow, 2004), this phenomenon is permanent.
Tinnitus is more prevalent in older adults (60 years and above) than in young, but age is not the sole factor for the onset of tinnitus and it can occur at any age.
There are interventions available for tinnitus however there is presently no cure (Eggermont & Roberts, 2004).
Tinnitus has no objective test in humans and relies on patients reporting the symptoms to an audiologist.
Much of tinnitus research relies on animal models but one of the most important confounds is that animals may not even be conscious of their tinnitus as would a human. Therefore human based research is vital.
Two current theories propose that tinnitus results from neural plasticity in response to reduced input from the inner ear as a result of hearing loss. The first theory posits that this plasticity arises in the auditory brainstem, the earliest stage of neural processing, as a result of homeostatic mechanisms that increase neural gain to balance the reduced neural input (R Schaette & McAlpine, 2011). The second theory posits that plastic changes occur at the auditory cortex with a rearrangement of the tonotopic map, this is known as cortical reorganisation (Eggermont & Roberts, 2004).
These theories will be tested in human subjects using a variety of EEG and psychophysical measures in control and tinnitus subject groups.