Training-induced enhancements in speech-in-noise perception and their association with medial olivocochlear efferent system plasticity

Objectives This study aimed to investigate the relationship between training-induced changes in speech-in-noise (SPIN) perception and the functioning of the medial olivocochlear bundle (MOCB), a key efferent auditory pathway. Specifically, it examined whether SPIN training results in measurable changes in contralateral suppression of otoacoustic emissions (CSOAEs) - an index of MOCB activity and whether such changes predict improvements in SPIN performance. Design Twenty-six normal-hearing adults (aged 18–55 years) with SPIN scores below 80% at − 5 dB SNR participated in the study. Participants were randomly assigned to a SPIN training group ( n = 13) or a placebo group ( n = 13). All underwent pre- and post-training assessments of SPIN (SNR-50 scores) and MOCB function (CSOAEs). The SPIN training group completed 12 sessions over two weeks involving perceptually demanding tasks with speech stimuli in various types of background noise. The placebo group engaged in passive video-watching tasks. CSOAE magnitude was derived from transient evoked otoacoustic emissions with and without contralateral acoustic stimulation. Results The trained group showed significant improvements in both CSOAE magnitude and SNR-50 ( p <.05), whereas the placebo group did not. A strong negative correlation was observed between changes in CSOAE magnitude and SNR-50 ( r = -.712, p = .006), indicating that greater MOCB activity was associated with better SPIN performance. Regression analyses confirmed that training-related changes in CSOAE significantly predicted improvements in SNR-50 (R² = 0.507), suggesting MOCB plasticity. Furthermore, participants with lower baseline CSOAE magnitudes exhibited larger training-induced gains. Conclusions SPIN training resulted in significant improvements in both perceptual and physiological measures of auditory processing. The findings support the role of the MOCB in the regulation of speech perception in noise and demonstrate its capacity for plasticity following targeted auditory training. Overall, the study highlights the potential of SPIN training to enhance efferent auditory system function and supports its consideration as an intervention strategy for individuals with poor speech-in-noise perception.