Effects of site-specific level adjustments on speech recognition with cochlear implants

摘要

ObjectivesModulation detection thresholds (MDTs) vary across stimulation sites in a cochlear implant electrode array in a manner that is subject and ear specific. Previous studies have demonstrated that speech recognition with a cochlear implant can be improved by site-selection strategies, where selected stimulation sites with poor modulation sensitivity are removed from a subject’s processor MAP. Limitations of site-selection strategies are that they can compromise spectral resolution and distort frequency-place mapping since the frequencies assigned to the removed sites are usually reallocated to other sites and site bandwidths are broadened. The objective of the current study was to test an alternative approach for rehabilitation that aimed at improving the across-site mean (ASM) MDTs by adjusting stimulation parameters at the poorly-performing sites. Based on previous findings that modulation detection contributes to speech recognition and improves significantly with stimulus level, we hypothesized that modulation sensitivity at the poor sites can be improved by artificially increasing stimulation levels at those sites in the speech processor, which then leads to improved speech recognition.