Recipient organisationBionics InstituteSource-published name: The Bionics Institute
Funding£221K
PeriodMay 2025 — Apr 2028
In plain English
AI plain-English summary
Cochlear implant users struggle to hear speech in a noisy room because the devices cannot capture the fine timing of sound. Most implants fire electrical pulses one after another to avoid current spreading across the inner ear, but this misses the rapid changes in sound waves that the brain needs to pick out a single voice from background chatter. Analogue stimulation—which sends a continuous electrical signal—preserves those timing details and gives users a more natural sound, yet the current spreads too widely to work across multiple channels at once. This project tests whether light can solve that problem. The researchers will genetically modify auditory neurons in mice to respond to light, then deafen the animals and implant either optical or electrical multi-channel devices. They will compare analogue and pulsed stimulation strategies, measuring how precisely each method encodes sound timing and how independently separate channels can operate. If optical analogue stimulation confines the signal more tightly than electricity does, it could restore the fine temporal and spectral resolution that current implants lack. That would mean better speech comprehension in noise, improved music perception, and more accurate sound localisation for users—a direct upgrade to a device that already helps hundreds of thousands of people.
View original technical description
Most cochlear implants utilise a pulsed coding strategy, stimulating electrodes sequentially to avoid overlapping currents. However, this strategy fails to capture fine changes in the timing of sound information critical for speech comprehension in noise, sound localisation and perception of pitch and timbre. Analogue stimulation provides a more precise and natural representation of the fine temporal structure of incoming acoustic waveform compared to pulsatile stimulation. Indeed, users of simultaneous analogue stimulation have reported a more pleasant sound experience and enhanced music perception. However, wide current spread from electrodes significantly restricts the feasibility and effectiveness of simultaneous electrical analogue stimulation. We hypothesise that applying analogue stimulation across multiple channels with greater spatial precision could improve both temporal and spectral resolution compared to pulsed stimulation methods. We recently demonstrated improved spatial precision via optical stimulation, enabled by optogenetics where neurons are genetically modified to respond to light. In this proposal, transgenic mice will be used with auditory neurons modified to be light-sensitive. The mice will be chemically deafened and implanted with either electrical or optical multi-channel implants. We will apply analogue and pulsatile strategies for both optical and electrical stimulation. We will examine neural response characteristics to measure how well the stimulus is encoded, such as spread of activation and vector strength analysis of neuronal phase locking to different modulation frequencies and amplitudes. We will also examine the independence of the stimulating channels by measuring the interactions between two channels stimulated simultaneously at different channel spacings. In addition, we will evaluate the ability to discriminate speech tokens in varying levels of background noise.
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