What the eyes tell us about listening: The neural and cognitive correlates of pupil dilation as measure of listening effort.

Currently, there is an urgent need for a well-validated tool to objectively
examine listening load in the field of Audiology (Arlinger et al., 2009;
Edwards, 2007; Fraser et al., 2009; Rönnberg et al., 2008). Pupil dilation is a
promising candidate for an accurate, relatively inexpensive, and unobtrusive
physiological listening load index. This study will provide the basis for the
interpretation of pupillometry as measure of listening effort.

The aim of the study is to strengthen the basis for a new application of
pupillometry (i.e., the measurement of pupil dilation) within the field of
Audiology. We will compare the pupil response during listening to speech in
noise to the activation in brain regions involved in listening. Insight into
the neural correlates of the pupil response will aid us in the interpretation
of differences in the pupil response between conditions/individuals.

Experimental study combining functional Magnetic Resonance Imaging (fMRI) and
pupillometry. The pupil response and brain activation will be expressed
relative to the response to listening to noise or in silence (baseline
conditions). Brain activation will be examined using fMRI. We will assess in
which brain regions the activation correlates with the pupil response across
listening conditions. We will additionally examine group effects (i.e., effects
of age and hearing loss) on the test performances, the pupil response and the
brain activation during listening.
Subjects additionally perform a working memory and a verbal inference-making
test. We will examine the correlation coefficients between the test
performances and speech intelligibility (percentage correct word repetition),
pupil dilation and brain activation.

Participating with this study does not involve any health risks with careful
observation of approved safety procedures for audiological testing, fMRI and
pupillometry. Pupillometry is based on recordings of a camera emitting
infra-red light at a power well below the standard safety guidelines. fMRI is a
non-invasive technique based on the natural magnetic properties of oxygenated
blood.