Power-efficient ramped stimulation in a fully implantable cochlear implant

Area of Science:

• Biomedical Engineering
• Neuroscience
• Auditory Prosthetics

Background:

• Cochlear implants (CIs) restore hearing via electrical nerve stimulation.
• Conventional rectangular pulses may not be optimally energy-efficient.
• Fully implantable CI systems require reduced power consumption.

Purpose of the Study:

• To compare the efficacy of ramped vs. rectangular pulse shapes for neural activation and energy efficiency in a fully implantable CI (FICI).

Main Methods:

• In vivo guinea pig model with a custom FICI system.
• Recorded electrically evoked auditory brainstem responses (eABRs) to four pulse shapes (Rectangular, RampUp, RampDown, RampLong).
• Analyzed waveform spectra and medium attenuation for transmission efficiency.

Main Results:

• Ramped waveforms produced larger eABR amplitudes, steeper input-output functions, and shorter latencies than rectangular pulses.
• Ramped pulses (RampUp, RampLong) showed 19-22% improved power efficiency at subthreshold levels after accounting for medium losses.
• Single-subject feasibility study demonstrated significant findings.

Conclusions:

• Ramped stimulation offers a promising strategy to enhance neural activation and improve power efficiency in CIs.
• These findings are particularly relevant for developing next-generation, fully implantable devices with longer battery life.