SOMATOSENSORY, PROPRIOCEPTIVE, AND SYMPATHETIC ACTIVITY IN HUMAN PERIPHERAL-NERVES

Compared volleys induced by artifical stimuli can be recorded from peripheral nerves of human subjects with extraneural electrodes. In contrast, the study of the normal traffic of impulses requires other methods. A powerful technique for recording this type of activity with percutaneously inserted intraneural electrodes was introduced in 1966. The development of the technique was promoted by interest in studying somatosensory and proprioceptive mechanisms in organisms with an intact sensorium and intact volition, particularly human subjects. This method opened up the possibility of investigating a number of neural mechanisms and is has been used mainly for studies of proprioceptive mechanism, tactile and nociceptive cutaneous activity, and efferent sympathetic discharges. In addition, cutaneous thermosensitive activity and oral mechanosensitive activity have been analyzed. Single-unit activity has been recorded from large myelinated nerve fibers and from unmyelinated nerve fibers, whereas rather few recordings from small myelinate fibers have been reported. In addition, multiunit activity from myelinated and unmyelinated fibers has been studied. Pathological mechanisms as well as normal conditions have been analyzed. Our aim here is to review findings extracted by recording impulses in human nerves with emphasis on the implications these findings may have on current theories within a number of fields. As far as it is feasible, the findings from human subjects are related to knowledge based on studies in other species. This review is based on reports published or known to be in the process of publication when the article was being written.