“The sound of speech has two components in the inner ear. One component consists of high frequency variations in the sound. The other component, known as the ‘envelope’, describes the outermost shape of the sound of speech”, says Anders Fridberger, professor of neuroscience at Linköping University, and one of two principal authors of the article.
Coding of speech-like sound
“But until now we have not known how the inner ear decodes the envelope of the speech signals. This is the new result we are presenting”, says Anders Fridberger.
The inner ear produces tiny electrical currents whenever sound enters – it converts sound to electrical impulses. These are led through the auditory nerve to the brain. By placing small electrodes into the ear canal of experimental subjects, and placing electrodes close to the cochlea of patients who have undergone surgery, the researchers have been able to record the way in which the inner ear codes speech-like sound.
Characteristic electrical signals
“This is both remarkable and surprising”, says Anders Fridberger.
Understanding inner ear function
The discovery is an important addition to our understanding of how the inner ear functions. The inner ear is embedded in a large bony structure, which makes it difficult to access and study it. Thus, diagnosing the exact location of damage to the inner ear is currently difficult.
“We believe that our results will improve diagnostic procedures for various hearing impairments, something that is sorely needed. Much remains to be done, however”, cautions Anders Fridberger.
Translation: George Farrants
