Unilateral hearing loss (UHL) ¿profound deafness in one ear and normal hearing in the contralateral ear- represents a hot topic in auditory cognitive neuroscience. After years of underinvestigation, due to next to normal behavioural performances, the UHL population has been suggested to present audiological, cognitive functions and cortical activity differences in comparison to normal hearing (NH) persons, especially during demanding conditions. For hearing impaired persons a main challenge is the detection and processing of auditory information with background noise, and this led to focus on the field of listening effort, mostly studied by questionnaires and scales; and by now a few studies were performed on UHL population. In addition, since the effort experienced by hearing impaired people during the speech production, also the related talking effort appears extremely worthy to be investigated through neurophysiology, that is by a totally novel approach. Moreover, since the implications of listening and talking on learning and communication their investigation in children appears crucial. The LI&TA project aims at assessing through neurophysiological measures the listening and talking effort elicited in UHL children during two phases of a typical school task: 1) listening to a story (listening effort phase); 2) during the following solicited verbal production concerning the story (talking effort phase). Furthermore, the task will be performed under signal to noise ratio typical of a real classroom environment. Through the Language ENvironment Analysis (LENA) system (a wearable audio recorder with an automated vocal analysis software) it will be possible to synchronize the listened and spoken material with neurophysiological data. Moreover, through the employment of the eyetracking will be also investigated the possible different reliance on the auditory or visual domain in the UHL children in comparison to NH controls, when facing challenging auditory conditions.
The LI&TA project presents some elements of relevance and innovation summarized in the following keypoints:
1. UHL population
2. Combination of neurophysiological measures and LENA system
3. Investigation of the eye gaze distribution during audio-visual material observation
In relation to the first point, the UHL population has been underinvestigated for a long time since the average good audiroy performances in daily activity, but only very recently became a hot topic in auditory cognitive neuroscience research since cortical activity [Cartocci et al 2019] and cognitive functions patterns [Ead 2013] appear to be different from NH people. These results open different scenarios for the study of UHL children, needing further verification and that LI&TA project at least partially aims at addressing to: 1) the occurrence of neuroplasticity changes which overcame the unilateral deafferentation and resulted in providing good behavioral performances; 2) the experience of higher levels of listening and talking effort that could also explain some specific school difficulties in UHL children, not only circumscribed to the auditory domain, but possibly involving executive functions (e.g. working memory)
In relation to the second point, the proposed research represents the first time that the EEG methodology and the LENA device would be associated, this will allow a second by second estimation of the listening effort and talking effort features in children, during an ecological experimental setup. In addition, the presence of the background noise will simulate the school environment, so providing an estimation of the background auditory conditions-related effort experienced by UHL and NH children during an ordinary school activity execution. This will have implications for the intervention to be implemented in hearing impaired children while attending school lessons, such as the selection of specific place of seating for them, or amplification solutions for classrooms [Larsen & Blair 2008]. Moreover, the talking effort evaluation through neurophysiological features represents a totally unexplored field, in fact this issue has been approached to my knowledge only by self-report and performance-based evaluations.
Furthermore, concerning the third point, thanks to the investigation through the eyetracker, it will be elucidated whether the gaze distribution adopted by UHL children differ from the one of NH controls, during an auditory challenging condition, in order to get visual cues that could support the auditory information reception and interpretation. This investigation would evidence whether similarly to CI users [Schorr et al 2005] also UHL children would rely more on the visual than on the auditory domain in correspondence of challenging stimuli reception condition, therefore suggesting the presence of an altered multisensory integration in such population [Sharma and Glick 2016].
Finally, the LI&TA project finds welcome from internationally-relevant researchers since the currency of the topic and the innovative approach of here proposed, as witnessed by the letter of interests provided by Prof. Ulrika Löfkvist from University of Oslo, that since her previous experience with LENA system application on hearing impaired and NH children, expressed her interest in the preliminary results of LI&TA project in order to undertake further common research interests.