The Perception of Ramped Pulse Shapes in Cochlear Implant Users

Area of Science:

• Neuroscience
• Biomedical Engineering
• Audiology

Background:

• Current cochlear implant (CI) electric stimulation lacks power efficiency.
• Inefficient transformation of electric pulse information into auditory nerve responses is a key issue.
• Ramped pulse shapes are a novel paradigm proposed to improve stimulation efficiency.

Purpose of the Study:

• To test if ramped pulses are more efficient than rectangular pulses for CI stimulation.
• To determine if rising ramps are more efficient than declining ramps.
• To compare charge efficiency and discriminability of different pulse shapes.

Main Methods:

• Seven cochlear implant (CI) users participated in the study.
• Evaluated rectangular, rising ramped, and declining ramped pulse shapes.
• Measured charge efficiency, discriminability, and threshold variability.

Main Results:

• Ramped pulses required reduced charge but increased peak current amplitudes at threshold and most comfortable levels.
• Only one participant could discriminate between equally-loud ramped and rectangular pulses.
• No significant difference was found between rising and declining ramped pulses.

Conclusions:

• Ramped pulses show some charge efficiency benefits compared to rectangular pulses in CIs.
• The direction of the ramped slope does not significantly impact efficiency or perception.
• Most CI users cannot perceive differences between ramped and rectangular pulse shapes.