Can we measure evoked responses to speech?

Abstract

Our research group is exploring whether it may be possible to optimise hearing aids for individuals using brain responses to real world stimuli. Hearing for speech is the primary concern of most hearing aid users hence the initial phase of our project has been to explore the reliability of speech evoked responses.

For short speech tokens such as ‘da’ brainstem and cortical responses can be reliably measured. However it is debatable how representative of real speech such short stimuli are, or whether responses to such stimuli represent detection or intelligibility. Another issue to consider is whether hearing aids will amplify short speech tokens in the same way that that they amplify running speech. Using more complex stimuli may alleviate this problem.

At the brainstem level both onset and modulation following responses can be detected within a few minutes using short speech tokens, words or short sentences, but with significant intersubject variability. Although cortical responses to running speech have been reported, we find these challenging to measure in reasonable clinical time scales. A new correlation based approach developed at Imperial University can be used to measure brainstem responses to running speech and this appears sensitive to the speech intelligibility.

The next phase of the study will be to explore the use of such measures to evaluate hearing aid fittings.

This work is funded by Engineering and Physical Sciences Research Council grant EP/M026728/1 and is joint between the Universities of Southampton, Imperial College and Manchester and the Interacoustics Research Unit.

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