Processing Effort in Cochlear Implant Users- A Pupillometry Study

Background: Everyday communication requires understanding speech in adverse listening situations. Competing background noise degrades the target speech which makes following a conversation effortful in particular for people with a hearing loss.

Objectives: This study aimed to gain better insights into processing effort required for speech communication in Cochlear Implant (CI) users by combing a dual-task paradigm with pupillometry.

Methods: A dual-task paradigm was tested with 25 CI users and 25 age-matched normal-hearing participants (NH). Sentences were presented via loudspeaker within a 4-talker masker. Participants’ task was to repeat back the final word of each sentence. After a list of sentences, they had to recall back as many of the final words as possible. Simultaneously, pupil dilation was recorded to monitor the allocation of cognitive resources during the dual-task and to quantify processing effort.

Results: Increased pupil dilation during stimulus presentation indicated effort allocated for listening and processing the sentence (referred to as listening effort), while larger pupil dilation during the recall indicated memory processing. In conditions with low task demands, CI users showed increased listening effort while smaller pupil dilations were observed in CI users compared to NH in situations with increased task demands.

Conclusions: By combining a dual-task with pupillometry, we gained insights into how CI users allocate their cognitive resources during recognizing and memorizing speech. It is speculated that CI users have to allocate more recourses for listening and processing the degraded speech compared to NH and, thus, less recourses are left for recalling speech.