Millions of people worldwide experience hearing loss, significantly impacting their ability to communicate and connect with the world. While existing solutions like cochlear implants can be effective, they are not suitable for all patients. Now, a team of researchers has explored a novel approach to restore sound perception using a spinal computer-brain interface (SCBI). This innovative technology leverages existing medical implants for spinal cord stimulation (SCS), typically used for chronic pain management, and converts sound information into electrical patterns that stimulate the spinal cord. In a series of experiments, the researchers demonstrated that participants could successfully identify a variety of everyday sounds, such as ringing phones, vehicle engines, and musical instruments, based solely on the resulting spinal cord stimulation patterns. The findings suggest that SCBI has the potential to serve as a new sensory substitution device for individuals with hearing loss, offering an alternative or complementary solution to existing treatments. This research paves the way for further advancements in using the spinal cord as a gateway to restore lost sensory functions. Hearing loss, cochlear implants, spinal cord stimulation, sensory substitution, computer-brain interface
Addressing the Unmet Need for Hearing Restoration
Millions of people worldwide experience moderate to complete hearing loss, significantly impacting their ability to communicate and connect with the world around them. Due to the aging population, the prevalence of hearing loss is expected to rise further, with an estimated 700 million people affected by 2050. While solutions like cochlear implants (CIs) have gained widespread use and can offer remarkable benefits in some cases, they are not suitable or available for all patients. Furthermore, a significant portion of CI recipients still struggle with poor long-term outcomes, such as limited word or sentence recognition.
Exploring Spinal Cord Stimulation for Sensory Substitution
To address this unmet need, a team of researchers has explored a novel approach: using a spinal computer-brain interface (SCBI) to restore sound perception. This innovative technology leverages existing medical implants for spinal cord stimulation (SCS), which is an established therapy for chronic pain management. The researchers hypothesized that by translating acoustic stimuli into spinal cord stimulation patterns, recipients could learn to interpret these inputs as sounds, effectively restoring their sense of hearing.
Methodology: Translating Sounds into Spinal Stimulation
The researchers recruited 13 patients who were undergoing SCS implantation for chronic pain management. During the trial phase, when the SCS leads were externalized, the researchers conducted two experiments to assess the participants’ ability to recognize and differentiate between various sound stimuli based solely on the resulting spinal cord stimulation patterns.
The researchers first established personalized “perceptual channels” for each participant, where specific stimulation patterns elicited distinct sensations on the body. They then converted a variety of everyday sounds, such as ringing phones, vehicle engines, and musical instruments, into time-varying electrical stimulation patterns tailored to each participant’s perceptual channels.
In the first experiment, participants were trained to recognize and identify these sound-derived spinal stimulation patterns. The results showed that, on average, participants achieved an accuracy of 72.8% in correctly identifying the sounds, significantly above the 33.3% chance level. Interestingly, the researchers found a positive correlation between the bitrate (information transfer rate) of the spinal stimulation and the participants’ recognition accuracy.
Exploring the Role of Stimulation Bitrate
To further investigate the impact of stimulation bitrate, the researchers conducted a second experiment. Participants were asked to compare pairs of spinal stimulation patterns and determine whether they were the same or different. When the bitrate was reduced, the participants’ ability to discriminate between the patterns significantly declined, demonstrating the crucial role of information throughput in the SCBI’s performance.
These findings suggest that SCBI can effectively convey sound information through spinal cord stimulation, with the potential to serve as a novel sensory substitution device for individuals with hearing loss. The researchers believe that by enhancing the stimulation fidelity and bitrate, SCBI could become a viable complement or alternative to existing auditory prostheses, such as cochlear implants.
Potential Applications and Future Directions
The SCBI approach offers several advantages over traditional sensory substitution methods. Unlike external wearable devices, the SCBI system can be more compact and less obtrusive, as it utilizes implanted electrodes. Additionally, the SCBI can achieve higher bitrates compared to vibrotactile devices, allowing for more detailed and nuanced sound information to be conveyed.
One particularly promising application of the SCBI is for individuals with hearing loss due to damage to the auditory nerve, such as those with neurofibromatosis type 2 or vestibular schwannomas. These patients are often not suitable candidates for cochlear implants, as they require a functional auditory nerve. The SCBI, which bypasses the auditory nerve and directly stimulates the spinal cord, could offer a viable solution for this underserved population.
Future research will focus on further enhancing the SCBI’s bitrate and stimulation fidelity, assessing long-term training effects, and exploring the integration of SCBI with other auditory aids, such as cochlear implants, to provide a comprehensive approach to hearing rehabilitation. By leveraging the vast capacity of the somatosensory system to encode complex sensory experiences, the SCBI holds the promise of revolutionizing the way we address hearing loss and significantly improving the quality of life for individuals with this debilitating condition.
Author credit: This article is based on research by Gabriella Miklós, László Halász, Maximilian Hasslberger, Emilia Toth, Ljubomir Manola, Saman Hagh Gooie, Gijs van Elswijk, Bálint Várkuti, Loránd Erőss.
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