In this study, patients with Usher syndrome were shown to have an olfactory deficit compared to the normal population. Usher syndrome patients needed a higher concentration of oderant to perceive a smell. Using fMRI it was also shown that Usher syndrome patients' prefrontal cortex (processing part of the brain) was more active, likely as a means to compensate for the relative under-stimulation.
What this means for Usher syndrome: Usher syndrome affects hearing and vision due to damaged cilia structure in the retina and inner ear. The olfactory system also has sensory input cells with cilia. In the past, there was not enough research to definitively say that Usher syndrome causes difficulty with sense of smell. This article suggests that in the near future, Usher patients will be able to receive a diagnosis for the lack of smell using functional neuroimaging.