Experimental assessment of polyphonic tones with cochlear implants

Area of Science:

• Auditory Neuroscience
• Bioelectrical Engineering
• Speech and Hearing Science

Background:

• Music perception, particularly polyphony, is challenging for cochlear implant (CI) users due to impaired pitch and harmony encoding.
• Current CI processing strategies struggle with simultaneous tones, hindering musical appreciation.

Purpose of the Study:

• To investigate the ability of CI users to discriminate tones with one and two modulation frequencies using direct electrical stimulation.
• To assess the impact of electrode location (apical, middle, basal) on tone discrimination.

Main Methods:

• CI users identified the number of modulation frequencies in stimuli delivered via direct electrical stimulation.
• One modulation frequency stimuli were presented on single basal, middle, or apical electrodes.
• Two modulation frequency stimuli were presented on electrode combinations (apical-basal, apical-middle) or a single apical electrode.

Main Results:

• CI users successfully identified one and two modulation frequencies significantly above chance across all tested electrode configurations.
• Performance was highest for single apical/middle electrodes and apical-basal combinations.
• Discrimination remained above chance even when two frequencies were presented on a single apical electrode.

Conclusions:

• Direct electrical stimulation enables CI users to perceive concurrent modulation frequencies.
• Future CI sound processing strategies could leverage concurrent modulations on single or multiple electrodes to improve polyphonic perception.
• Enhanced perception of complex tones may lead to better music and language understanding for CI users.