Perception and Mechanical Properties of the Pacinian Corpuscle

Abstract

The sense of touch is processed by the somatosensory system in which mechanoreceptors are the sensory neurons that translate mechanical stimuli into neural impulses by using specialized mechanoreceptive end organs. Pacinian corpuscles (PCs), located primarily in the hairless skin of the hands and feet, are the mechanoreceptor responsible for sensing low--amplitude, high--frequency vibrations (80-1000 Hz). In this thesis, I explored how vibrotactile perception is mediated by the PCs using a combination of computational modeling, benchtop experiments on donor tissue, and psychophysical tests. There are several mechanical models of the PC, and the first part of this thesis demonstrated that a multiphysics model of a single PC contained enough details to recapitulate the trend of observed discriminability of human subjects. We showed that discriminability of sinusoidal vibrations increases as the frequency difference between the pairs increase, and we found that complex waveforms with two frequency components were more difficult to discriminate and did not follow a discernible trend. Next, we investigated the effect that Dupuytren disease (DD) has on vibrotactile perception at frequencies within the PC's range. Dupuytren disease is a progressive hand disorder in which growth and densitification of fibrous tissue in the palms eventually causes the affected fingers to bend irreversibly. DD usually presents clinically after the age of 50, affects about 3 per 10,000 adults, and is associated with alterations to the size and the internal structure of PCs. By measuring vibrotactile sensitivity in healthy and DD subjects, we found that women are more sensitive to high--frequency vibrations than men and that men with DD may exhibit reduced sensitivity compared to men without DD. We also found that, for patients in which DD presents unilaterally, the finger with DD is less sensitive than the corresponding finger on the unaffected hand. These data may serve as a useful reference to future DD researchers and may facilitate development of novel diagnostic or prognostic protocols. Finally, we designed a system to measure the viscoelastic properties of the PC and tested isolated human cadaveric PCs from donors with and without DD to better understand how the mechanoreceptor's viscoelastic properties affect vibrotactile perception.