Real-world listening effort in adult cochlear implant users

Cochlear implants (CI) are a treatment to provide a sense of hearing to individuals with severe-to-profound sensorineural hearing loss. Even when optimal levels of intelligibility are achieved after cochlear implantation, many CI users complain about the effort required to understand speech in everyday life contexts. This sustained mental exertion, commonly known as “listening effort”, could negatively affect their lives, especially regarding communication, participation, and long-term cognitive health. This thesis aimed to evaluate the listening effort experienced by CI recipients in real-world sound scenarios. The research focused on social listening situations that are particularly common in everyday life such as having conversations in a busy café or communicating through video call. Additionally, some situations that prevailed during the COVID-19 pandemic were also examined (e.g., listening to someone who is wearing a facemask). Multimodal measures of listening effort were employed throughout the research project to obtain a comprehensive assessment. Nonetheless, the primary focus was on measures that quantify objectively the cognitive demands of listening through a CI. To that end, we used a combination of physiological measures, functional near infrared spectroscopy (fNIRS) brain imaging and simultaneous pupillometry, both of which are compatible with CIs and capable of providing insights into the neural underpinnings of effortful listening. We also proposed a novel approach to quantify “listening efficiency”, an integrated behavioural measure that reflects both intelligibility and listening effort. We successfully applied these assessments to 168 CI users and 75 age-matched normally hearing (NH) controls who were recruited throughout the project. We found that CI users experienced high levels of listening effort, even when their intelligibility was optimal under highly favourable listening conditions. Objective measures revealed that CI listeners exhibited significantly inferior listening efficiency than NH controls when listening to speech under moderate levels of cafeteria background noise and when attending online video calls. Physiologically, they showed elevated levels of arousal as revealed by larger and prolonged pupil dilations to baseline compared with NH controls, suggesting high cognitive load and increased need for recovery. The importance of visual cues was evident; the presence of video and captions benefited CI recipients by improving considerably their listening efficiency during online communication. These results were consistent with their subjective ratings of effort, both in the experiments and in daily life. These findings provide objective evidence of the cognitive burden endured by CI listeners in everyday life. In addition, the objective assessments proposed were proved feasible to quantify the performance and cognitive demands of listening through a CI. In particular, listening efficiency showed sensitivity to differences in task demands and between groups, even when intelligibility remained near perfect. We argue that listening efficiency holds potential to become a CI outcome measure

Real-world listening effort in adult cochlear implant users

Cochlear implants (CI) are a treatment to provide a sense of hearing to individuals with severe-to-profound sensorineural hearing loss. Even when optimal levels of intelligibility are achieved after cochlear implantation, many CI users complain about the effort required to understand speech in everyday life contexts. This sustained mental exertion, commonly known as “listening effort”, could negatively affect their lives, especially regarding communication, participation, and long-term cognitive health. This thesis aimed to evaluate the listening effort experienced by CI recipients in real-world sound scenarios. The research focused on social listening situations that are particularly common in everyday life such as having conversations in a busy café or communicating through video call. Additionally, some situations that prevailed during the COVID-19 pandemic were also examined (e.g., listening to someone who is wearing a facemask). Multimodal measures of listening effort were employed throughout the research project to obtain a comprehensive assessment. Nonetheless, the primary focus was on measures that quantify objectively the cognitive demands of listening through a CI. To that end, we used a combination of physiological measures, functional near infrared spectroscopy (fNIRS) brain imaging and simultaneous pupillometry, both of which are compatible with CIs and capable of providing insights into the neural underpinnings of effortful listening. We also proposed a novel approach to quantify “listening efficiency”, an integrated behavioural measure that reflects both intelligibility and listening effort. We successfully applied these assessments to 168 CI users and 75 age-matched normally hearing (NH) controls who were recruited throughout the project. We found that CI users experienced high levels of listening effort, even when their intelligibility was optimal under highly favourable listening conditions. Objective measures revealed that CI listeners exhibited significantly inferior listening efficiency than NH controls when listening to speech under moderate levels of cafeteria background noise and when attending online video calls. Physiologically, they showed elevated levels of arousal as revealed by larger and prolonged pupil dilations to baseline compared with NH controls, suggesting high cognitive load and increased need for recovery. The importance of visual cues was evident; the presence of video and captions benefited CI recipients by improving considerably their listening efficiency during online communication. These results were consistent with their subjective ratings of effort, both in the experiments and in daily life. These findings provide objective evidence of the cognitive burden endured by CI listeners in everyday life. In addition, the objective assessments proposed were proved feasible to quantify the performance and cognitive demands of listening through a CI. In particular, listening efficiency showed sensitivity to differences in task demands and between groups, even when intelligibility remained near perfect. We argue that listening efficiency holds potential to become a CI outcome measure