Research Fellows Directory
Dr Stuart Johnson
University of Sheffield
Sound is detected by extremely sensitive sensory receptors named hair cells that are located in the auditory organ, the cochlea. The name hair cell derives from the hair-like elements (stereocilia) that project from the tops of hair cells. When sound enters the ear it causes hair cell stereocilia to vibrate initiating the conversion of sound into an electrical signal within the cell. This electrical signal induces the release of chemicals (neurotransmitters) from hair cells, the purpose of which is to activate adjacent auditory nerve fibres so the information gathered can be relayed to the brain and enable us to hear.
The human ear can process and localize sounds ranging from the high-pitch squeak of a mouse to the low rumble of thunder in the distance. In order to process such a remarkable sound frequency range, the cochlea is organised such that hair cells at one end encode low-frequencies and those at the other high-frequencies. Hair cells have evolved intrinsic specializations that could enhance signalling at their specific frequency. My research aims to determine how these hair cell differences shape the initial nerve impulse to the brain and how they make them adept at signalling at their characteristic sound frequency.
An understanding of normal hair cell function is vital to support research aimed at revealing the causes of, and developing cures for hearing loss. There are numerous therapies for the prevention of hearing loss and evidence that cell regeneration may be possible through gene and stem cell therapy. For these to be feasible it is crucial to have an understanding of how the hair cells develop and the properties that make them specialized for accurate sound detection. Advances generated by this work offer a social and economical benefit since they will contribute, in the long term, to decreasing the number of people with hearing loss, which costs the UK billions of pounds annually.
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