ABSTRACT
Certain nerves can be found by palpation and knowledge of specific anatomical landmarks, but generally an external stimulating electrode is used to locate the nerve by delivering weak electrical pulses through the skin. The site of lowest threshold for evoking pins-and-needles in the cutaneous distribution of the nerve, and/or twitches in the innervated muscles, is then marked as the site for inserting the microelectrode. Single-unit recordings have also been made from sensory nerve fibers innervating the teeth, via microelectrodes inserted into the inferior alveolar nerve through the open mouth. The majority of recordings from large-diameter nerve fibers have positive-going spikes, which reflect impalement of the myelin sheath by the electrode tip in the internode region. Negative-going spikes, indicating proximity of the electrode tip to a node of Ranvier, occur in only a few per cent of unitary recordings.
