Researchers at EPFL, a public research university in Switzerland, have introduced a flexible auditory brainstem implant (ABI) that offers enhanced precision in hearing.
According to EPFL, this new technology, tested on macaques, promises a significant improvement over existing ABIs by closely conforming to the brainstem’s curved surface.
For individuals with severely damaged cochlear nerves, traditional cochlear implants are ineffective. Auditory brainstem implants serve as an alternative, yet current models are hindered by rigid designs that fail to maintain optimal tissue contact.
This limitation often leads to undesirable side effects, necessitating the deactivation of many electrodes. Consequently, most users only experience indistinct sounds with poor speech comprehension.
The research team at EPFL’s Laboratory for Soft Bioelectronic Interfaces has created a soft thin-film ABI using micrometer-scale platinum electrodes embedded in silicone. This configuration forms a flexible array that enhances tissue contact and reduces adverse effects by minimising unintended nerve activation.
EPFL Laboratory for Soft Bioelectronic Interfaces head Stéphanie Lacour said: “Designing a soft implant that truly conforms to the brainstem environment is a critical milestone in restoring hearing for patients who can’t use cochlear implants. Our success in macaques shows real promise for translating this technology to the clinic and delivering richer, more precise hearing.”
Unlike standard surgical evaluations, the researchers conducted behavioural tests on macaques with intact hearing to assess how effectively these animals could discern electrical stimulation patterns akin to natural sound perception.
Emilie Revol, co-first author of the study, trained the macaques to identify whether consecutive tones were identical or different using a lever mechanism.
Revol said: “Half the challenge is coming up with a viable implant, the other half is teaching an animal to show us, behaviourally, what it actually hears.”
The soft ABI was gradually introduced alongside normal tones until only the soft ABI was used for stimulation. Results indicated that the macaques perceived electrical pulses almost like real sounds.
EPFL’s novel design leverages soft bioelectronic interfaces for improved electrode-tissue contact.
The researchers claim that the ultra-thin silicone structure of the new ABI allows better adherence to the complex shape of the cochlear nucleus. This potentially lowers stimulation thresholds and activates more electrodes for high-resolution hearing.
The study observed no off-target effects such as discomfort or muscle twitching in macaques subjected to electrical currents within tested ranges.
Despite promising results, further research and regulatory approvals are necessary before commercialisation of the soft ABI can commence.
Long-term reliability and medical-grade materials are vital for human application. The EPFL team’s prototype demonstrated stability over several months in animal tests without noticeable electrode migration, suggesting progress toward addressing similar issues faced by current ABIs.
