RESUMO
Background: One factor which influences the speech intelligibility of cochlear implant (CI) users is the number and the extent of the functionality of spiral ganglion neurons (SGNs), referred to as "cochlear health." To explain the interindividual variability in speech perception of CI users, a clinically applicable estimate of cochlear health could be insightful. The change in the slope of the electrically evoked compound action potentials (eCAP), amplitude growth function (AGF) as a response to increased interphase gap (IPG) (IPGEslope) has been introduced as a potential measure of cochlear health. Although this measure has been widely used in research, its relationship to other parameters requires further investigation. Methods: This study investigated the relationship between IPGEslope, demographics and speech intelligibility by (1) considering the relative importance of each frequency band to speech perception, and (2) investigating the effect of the stimulus polarity of the stimulating pulse. The eCAPs were measured in three different conditions: (1) Forward masking with anodic-leading (FMA) pulse, (2) Forward masking with cathodic-leading (FMC) pulse, and (3) with alternating polarity (AP). This allowed the investigation of the effect of polarity on the diagnosis of cochlear health. For an accurate investigation of the correlation between IPGEslope and speech intelligibility, a weighting function was applied to the measured IPGEslopes on each electrode in the array to consider the relative importance of each frequency band for speech perception. A weighted Pearson correlation analysis was also applied to compensate for the effect of missing data by giving higher weights to the ears with more successful IPGEslope measurements. Results: A significant correlation was observed between IPGEslope and speech perception in both quiet and noise for between-subject data especially when the relative importance of frequency bands was considered. A strong and significant correlation was also observed between IPGEslope and age when stimulation was performed with cathodic-leading pulses but not for the anodic-leading pulse condition. Conclusion: Based on the outcome of this study it can be concluded that IPGEslope has potential as a relevant clinical measure indicative of cochlear health and its relationship to speech intelligibility. The polarity of the stimulating pulse could influence the diagnostic potential of IPGEslope.
RESUMO
BACKGROUND AND OBJECTIVES: The band-importance function (BIF) refers to a value characterizing the relative importance of different frequencies to speech intelligibility. The purpose of this study was to derive the BIF for the Korean standard sentence lists for adults (KS-SL-A). SUBJECTS AND METHODS: In this study, sentences from the KS-SL-A were used as the speech material. Twenty-six normal-hearing Korean listeners participated and intelligibility scores in 8 filters with 3 signal-to-noise ratio conditions were obtained. Based on the intelligibility score percentages, the BIF for the KS-SL-A was derived by using an established protocol. RESULTS: Band-importance weights varied across frequency bands. The most important frequency region was around 316 Hz (20.0%), and the importance of the frequency bands below the center frequency (CF) of 1,778 Hz was 59.6%. Therefore, low frequencies below the CF of 1,778 Hz were more important than high frequencies above the CF of 1,778 Hz. CONCLUSIONS: The BIF for KS-SL-A could be applied towards developing a hearing aid fitting formulae for Korean listeners.
RESUMO
BACKGROUND AND OBJECTIVES: The band-importance function (BIF) refers to a value characterizing the relative importance of different frequencies to speech intelligibility. The purpose of this study was to derive the BIF for the Korean standard sentence lists for adults (KS-SL-A). SUBJECTS AND METHODS: In this study, sentences from the KS-SL-A were used as the speech material. Twenty-six normal-hearing Korean listeners participated and intelligibility scores in 8 filters with 3 signal-to-noise ratio conditions were obtained. Based on the intelligibility score percentages, the BIF for the KS-SL-A was derived by using an established protocol. RESULTS: Band-importance weights varied across frequency bands. The most important frequency region was around 316 Hz (20.0%), and the importance of the frequency bands below the center frequency (CF) of 1,778 Hz was 59.6%. Therefore, low frequencies below the CF of 1,778 Hz were more important than high frequencies above the CF of 1,778 Hz. CONCLUSIONS: The BIF for KS-SL-A could be applied towards developing a hearing aid fitting formulae for Korean listeners.
