Anders Fridberger’s research deals with sensory neuroscience – how the inner ear converts sound into electrical impulses in the auditory nerve. This conversion, which has fundamental importance for the sense of hearing, depends on small protrusions found at the tops of the sensory cells in the inner ear.
To study the function of these stereocilia, my research group has developed a new type of confocal microscope that makes it possible to directly observe sound-evoked motion - we can ”see how we hear” – and the size and direction of the movements is obtained through optical flow calculations.
By using this technique, we demonstrated that rapid length changes of stereocilia occur on a cycle-by-cycle basis during sound stimulation. These length changes are important for the ear’s ability to convert sound into electrical signals, and the mechanisms that regulate stereocilia length are now the subject of study in the lab.
When we listen to sounds near the threshold of hearing, the sound-evoked movements within the hearing organ are less than 1 billionth of a meter. It is not yet clear how the sensory cells can use such a tiny stimulus, and to be able to study this process, we also use laser interferometry, which can measure cellular vibrations at the Angstrom level.
Loud sounds will alter the function of inner ear sensory cells, and the techniques mentioned above are also used for studying the physiological mechanisms underlying noise-induced hearing loss.
Medical treatments can protect sensory cells in animals, but we do not yet know whether this works in humans. In collaboration with the ENT clinics in Uppsala, Stockholm and Linköping, we started clinical trials of substances with potential inner-ear protective effects. If these treatments turn out to be effective, a protective treatment may become available for people exposed to loud sounds.
