Recently, researchers from Linköping University in Sweden have discovered the parts of the inner ear that process sounds such as speech and music seem to work differently than other parts of the inner ear, according to Science Daily.
The inner ear contains the cochlea. The cochlea’s job is to convert sound waves into neural signals, which are then sent to the brain (via the auditory nerve). Inside the cochlea is the organ of Corti – also known as the ‘spiral organ’), which contains the hair cells responsible for hearing.
The ‘high-frequency regions’ of the cochlea have been frequently studied. However, there is a problem inherent with trying to study the low frequency regions of the cochlea because this part of the inner ear is embedded in thick bone. (This means previous studies have only been done on dissected cochlea.)
Prior to this study in Sweden, no mechanical measurements of the low-frequency parts of ‘intact’ cochlea had been available.
In their study, the researchers used a sort of ‘optical ultrasound’ called ‘optical coherence tomography’ to capture images of the vibration in the (intact) cochlea when low-frequency sounds were played.
Anders Fridberger, professor of neuroscience at Linköping University said,
“We have been able to measure the inner ear response to sound without having to open the surrounding bone structures and we found that the hearing organ responds in a completely different way to sounds in the voice-frequency range. It goes against what was previously thought of how the inner ear works. This helps us understand the mechanisms that enable us to perceive speech and music. We hope that more knowledge about the capabilities of the ear will lead to better treatments for the hearing impaired.”
The cochlea is coiled in a spiral shape. If the cochlea were uncoiled, it would be about 33 mm long in women and 34mm in men.
The results have been published in PNAS, the Proceedings of the National Academy of Sciences.