Cochlear implant spectral bandwidth for optimizing electric and acoustic stimulation (EAS)

Area of Science:

• Audiology
• Neuroscience
• Biomedical Engineering

Background:

• Cochlear implantation with acoustic hearing preservation (EAS) is growing.
• Optimal EAS technology programming lacks definitive guidance.
• Previous studies on hearing aid (HA) and CI programming for EAS listeners show mixed results.

Purpose of the Study:

• To explore the effects of various EAS crossover frequencies on speech recognition and listening difficulty.
• To compare CI-alone, bimodal (CI+HA), and best-aided EAS (CIHA+HA) listening conditions.
• To investigate the relationship between CI cutoff frequency and spiral ganglion (SG) characteristic frequency.

Main Methods:

• 15 adult CI recipients with acoustic hearing preservation participated.
• Speech recognition in semi-diffuse noise was measured.
• Subjective listening difficulty was assessed.
• Three conditions were tested: CI-alone, bimodal (CI+HA), and best-aided EAS (CIHA+HA).

Main Results:

• No significant effect of low-frequency (LF) CI cutoff on speech recognition or listening difficulty was observed across the tested conditions.
• Both bimodal (CI+HA) and best-aided EAS (CIHA+HA) showed significant benefits over CI-alone listening.
• Best-aided EAS (CIHA+HA) provided additional benefits compared to bimodal hearing (CI+HA).

Conclusions:

• Current EAS crossover frequency settings, referenced to SG-place frequency, did not impact performance in this study.
• Bimodal and best-aided EAS listening significantly improve outcomes compared to CI-alone.
• Future research should examine SG-place-based fittings in larger, experienced EAS populations and newly activated users.