ABSTRACT
The remarkable security displayed by the linkage between Pacinian corpuscle (PC) sensory fibers and their target gracile neurones ensures a very high safety or security, and is in stark contrast to the dependence, at the Ia-motoneurone synapse, upon elaborate convergence and summation before motoneurone output can be generated. One of the explanations for the marked differences observed among the kinaesthetic and tactile fiber classes in their capacity to generate perceptual responses may be based on differences in their transmission characteristics across synaptic junctions in the somatosensory pathways. Although the above afferent classes contribute to tactile or kinaesthetic experience, there is quite striking evidence, when individual fibers are activated in conscious human subjects, of marked differences among the fiber classes in their capacity to generate a perceptual response. Individual PC fibers were activated in the experiments by means of vibration applied with a 200 µm diameter probe to individual corpuscles that could be visualized along the nerve or the interosseous membrane.
