Scientists have provided the first evidence in a new study published in Restorative Neurology and Neuroscience. The study suggests that a simple and inexpensive non-invasive speech-to-touch sensory substitution device has the potential to improve hearing in hearing-impaired cochlear implant patients, as well as people with normal hearing to better discern speech in various situations like learning a second language or trying to deal with the "cocktail party effect." The device can provide immediate multisensory enhancement without any training.
The lead investigator from the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Amir Amedi, Ph.D., said that despite recent advancements in hearing aid and cochlear implants, the most widespread surgical implant to restore audition, hearing-impaired users still encounter significant practical and social challenges with or without aids. In particular, these people struggle with understanding speech in challenging, noisy acoustic environments, especially in the presence of a competing speaker.
There is an expectation in the rise of that the number of sensory patients, and auditory deprived patients and as a result, it is crucial to develop efficient techniques for auditory recovery designed to convey the missing information to patients.
Dr. Amedi commented further that in a world that is becoming steadily more multisensory, there is a need to understand the mechanisms underlying multisensory perception and integration. Providing relevant information using the sense of touch can significantly help to hear.
With this current proof-of-concept, the study investigators hypothesized that they would be able to improve speech understanding under challenging conditions by exploiting the ability of the brain to integrate information coming simultaneously from different senses. The team designed a minimalistic auditory-to-tactile vibration delivered on two fingertips. They asked a group of non-native English speakers to repeat a series of sentences which was degraded by embedding them in speck-like noise.
The expectation is that participants could rely only on audition; their understanding of such sentences was poor. However, their sentence understanding significantly improved when they paired the degraded speech signal with complementary vibration delivered on the participants' fingertips. The vibration conveyed a specific set of frequencies known as fundamental frequencies that characterize speech signals.
Co-author of the study, Tomasz Wolak, Ph.D., Eng, Head of the Bioimaging Research Center, Institute of Physiology and Pathology of Hearing, World Hearing Center, Warsaw, Poland, said that their results carry essential implications for further research, as well as possible clinical and practical solutions. He noted further that the ability to hear through one's fingers could significantly help to hear. The approach of the scientists suggests that multisensory stimulations providing the same type of information (in this case spoken language conveyed through touch in addition to hearing) should be processed in the same brain region (in this case spoken language centers), ultimately then predicting that multisensory stimulations (both sounds and touch) should enhance perception.
