Objective measures in normal and cochlear implant listeners

Hamish Innes_Brown

Speaker: Hamish Innes-Brown 
Date: Friday 12 August 2016
Time: 10:00am – 11:00am
Location: Australian Hearing Hub, Level 1,  Lecture Theatre

Hamish will talk about two areas of research currently under way at the Bionics Institute in Melbourne: cochlear implant threshold estimation using cortical potentials, and  also touch on very recent work in normal-hearing listener looking at brain responses to changes in inter-aural phase.

Stimulation threshold levels for cochlear implants are currently set by manually adjusting current levels for individual electrodes until the patient reports that they perceive sound. This process is time consuming even in healthy adults, and impossible in young children or others who cannot provide verbal responses or follow instructions. For this reason, objective measures that detect stimulus-induced electrical activity generated in the auditory nerve and brainstem are sometimes used (ECAPs, EABRs) to set cochlear implant threshold levels. However, these measures do not correlate well with actual behavioural thresholds. Cortical activity, which may reflect more perceptually-related activity, is therefore a better candidate for objectively fitting cochlear implants. In this study we found strong correlations between cortical responses and behavioural thresholds (r = 0.93), suggesting that the cortical response may be more useful as an objective programming tool for cochlear implants than the auditory nerve response.

Hamish Innes-Brown is an NHMRC Early-Career Research Fellow at the Bionics Institute. He has a life-long interest in sensory aspects of sound, vision, and communication. At the Bionics Institute he is using brainwave recordings and perceptual tests to understand and improve the way that sounds are interpreted by people with hearing loss. Perceiving sounds properly is crucial for communication and function in complex social, education, and work environments.