The effect of unilateral and bimodal auditory stimulation on auditory perception and reaction time.

PURPOSE: This study aimed to evaluate the differences between unilateral cochlear implant (CI) use and bimodal auditory stimulation regarding speech perception in noise and auditory reaction times.

METHODS

This cross-sectional study included 26 adults (aged 18-53 years) with a unilateral CI and a contralateral hearing aid. Participants underwent free-field audiometry (FFA), Speech Reception Threshold (SRT) testing, the Turkish Matrix Test (TMT) in quiet and noise, and the Auditory Reaction Time Test (ARTT). Measurements were compared between unilateral (CI only) and bimodal (CI plus hearing aid) conditions.

RESULTS

Bimodal stimulation yielded significantly better free-field and speech reception thresholds compared to the unilateral condition (p < 0.001). In the TMT, speech perception thresholds improved with bimodal stimulation in both quiet (44.9 ± 8.7 vs. 53.7 ± 9.3 dB SPL) and noise (1.1 ± 3.1 vs. 4.3 ± 3.1 dB SNR) (p < 0.001). Additionally, simple auditory reaction times were significantly shorter in the bimodal condition (518.5 ± 51.9 ms) than in the unilateral condition (559.6 ± 54.6 ms) (p < 0.001). Similar improvements were observed in choice reaction times (p < 0.001).

CONCLUSION

Bimodal auditory stimulation significantly enhances auditory performance and reaction speed compared to unilateral CI use. These findings suggest that bimodal fitting improves binaural integration and processing efficiency, which is beneficial for speech intelligibility in challenging listening environments.