The Effect of Different Auditory Stimuli and Optokinetic Stimuli on Vestibulo-Ocular Reflex Function.

This study investigated how auditory stimuli and optokinetic stimulation modulate functional Head Impulse Test (fHIT) correct response rate (CR%) across semicircular canals (SCCs) and the associated cognitive load in healthy adults. Fifty participants (20-57 years) completed repeated-measures fHIT under four conditions: silence, music, white noise, and optokinetic stimulation. The CR% from all SCCs were recorded and workload was assessed with the NASA Task Load Index (NASA-TLX). Optokinetic stimulation produced the most significant CR% decrement (e.g., right lateral 90 vs. 100 in silence; p<0.001) and the highest workload (median NASA-TLX = 50). Auditory conditions produced minimal CR% changes. Across conditions, lateral SCCs were less affected than vertical SCCs by sensory and cognitive interference. Visual-vestibular conflict markedly reduced CR%, whereas auditory effects appeared indirect and attention mediated. These findings provide normative benchmarks for multisensory fHIT assessment.