Pacinian corpuscles and polyharmonic vibrations

Psychophysical and physiological experiments using low amplitude, high‐frequency vibrations which selectively activate Pacinian corpuscle mechano‐receptors have been employed to address the question: Can the vibrotactile system distinguish between pure and polyharmonic sinusoidal stimuli applied to the glabrous skin in the presence of concomitant changes in fundamental frequency and amplitude? Human subjects are presented with stimulus pairs in which a pure tone is paired with a tone having a significant second harmonic component. The fundamental frequency and amplitude of each member of the pair are varied independently so they typically differ in peak‐to‐peak amplitude and frequency composition as well as harmonic content. In addition, different phase relations between the fundamental and harmonic of the diharmonic tone are used. The subjects are asked to identify which member of the pair is diharmonic. Responses of Pacinian corpuscles to the same tone pairs are recorded from afferent fibers in the forelimb of the cat, using both on‐center and off‐center stimulation. The eventual goal is to collect similar data in primates in order to be able to describe the neural basis for the discrimination ability observed in the psychophysical tests.