Investigation of the effect of cognitive load on multisensory system in single-sided deafness

Objective: This study comprehensively examines the effects of single-sided deafness on postural balance. Static and dynamic balance were assessed using various test protocols, aiming to reveal the potential impacts of the side of hearing loss on postural stability. Additionally, the study aimed to identify potential differences in postural control resulting from the cognitive load imposed on individuals through a dual-task paradigm. Method: The study included individuals with left-sided hearing loss (n=15, age=34.1±14.1), right-sided hearing loss (n=15, age=36.1±14.7), and normal-hearing individuals (n=15, age=28.1±10.2). For balance assessment, all participants underwent the Flamingo Balance Test (FBT), the Timed Up and Go Test (TUG), and Computerized Dynamic Posturography (CDP). The dual-task paradigm used in the study was performed under conditions of noise and verbal fluency tasks. All dynamic balance assessments in the CDP test were conducted separately for both baseline (single-task) and cognitive (dual-task) conditions. In addition to evaluating composite balance parameters using CDP, the total displacement of the participants' center of gravity (COG) was also calculated and analyzed. Results: The study found that individuals with single-sided deafness had poorer postural balance performance compared to normal-hearing individuals. Specifically, individuals with left-sided hearing loss exhibited worse static balance (p<0.05). In terms of dynamic balance, individuals with right-sided hearing loss showed greater COG (center of gravity) sway in the absence of an additional cognitive task (p<0.05), whereas those with left-sided hearing loss demonstrated greater COG sway in the presence of an additional cognitive task (p<0.05). Furthermore, normal-hearing individuals exhibited significantly less postural sway during the additional cognitive task (including the presence of a steady noise source) compared to individuals with single-sided deafness (p<0.05). Conclusion: This study demonstrated that single-sided deafness could affect individuals' cognitive performance and the postural control mechanism, which requires multisensory processing. Additionally, it showed that analyzing COG sway in the evaluation of postural balance in individuals with single-sided deafness might provide more detailed data compared to composite balance scores and performance-based tests.