Researchers at the Sweden-based Karolinska Institutet have discovered four types of neurons in the inner ear (the peripheral auditory system), three of which have not been known to the science world before. The proper analysis of these neurons could play an important role in the development of new therapies for a variety of hearing disorders affecting millions across the globe, including age-related hearing loss and tinnitus.
When auditory waves reach the inner ear, they transform into electrical signals that are then transported to the brain through the nerve cells in ear’s cochlea. These cells were previously thought to be of two kinds: type 1 neurons and type 2 neurons, with type 1 being the ones that transmit most of the auditory data. Now, the study demonstrates that type 1 cells comprise three very different kinds of cells. This goes to show that there are three different routes and not one into the central auditory system.
The researchers undertook their study on mice with the help of a relatively new single-cell RNA sequencing mechanism. The research demonstrates that these three types of neurons potentially have a role to play in how sonic intensity, which is known as volume in simpler terms, is decoded. This function is necessary in times of conversations taking place in loud environments, decoding which relies on the ear’s ability of filtering out background noise. The function is also crucial to understand when getting to understand the various kinds of hearing disorders such as oversensitivity to sound and tinnitus.