Loes Beckers1,2, Svetlana Gerakaki3, Marc van Wanrooij3, Birgit Philips1, Wendy Huinck2, Emmanuel Mylanus2
1 Cochlear Ltd, Mechelen, BE; 2 Department of Otorhinolaryngology, Donders Institute for Brain, Cognition and Behaviour, Radboud university, Nijmegen, NL; 3 Department of Biophysics, Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, NL
Background: Profoundly deaf adults are currently treated with a cochlear implant (CI) yielding substantial hearing benefits. Nevertheless, speech understanding of CI users remains perturbed, especially in noisy environments and for those CI users suffering from considerable auditory-nerve degradation. Under these demanding situations, non-acoustic sources of information, such as prediction and memory, may become important. Here, we studied how effortful listening becomes, when neurocognitive mechanisms need to be activated while listening to a distorted speech signal through a CI vocoder.
Methods: Previous studies by Obleser et. al., (J. NeuroSci. 2012 vol:32) and Petersen et. al., (F. Psych. 2015, vol:6), implemented a suitable protocol to investigate inhibition, a mechanism involved in ignoring task-irrelevant information, and working memory load in listeners with normal hearing and various degrees of hearing loss. Neuronal alpha-band activity, associated with inhibition and storage, was assessed using EEG during an auditory digit working memory task, in which memory load and acoustic degradation were manipulated. We replicated this paradigm in normal hearing listeners and extended the paradigm by measuring pupil dilation.
Results: This is an ongoing study.
Conclusion: Based on the replicated study, we expect that alpha activity in the parietal lobe increases with increasing memory load and acoustic degradation. Furthermore, we expect that listening effort, and pupil dilation as its proxy, has a non-monotonic relationship to memory load and acoustic degradation. And that individual differences in coping strategies are reflected in pupil dilation and oscillation measures. The results of our study will help to aid audiological assessment and revalidation of CI users, as we will apply a similar paradigm to adult CI users to explore variability in speech perception performance due to top-down neurocognitive factors.