title: Far-field recording of the junctional potential generated by median nerve volleys at the wrist.
abstract: In 20 arms from 10 healthy subjects, the orthodromic median sensory volleys crossing the wrist gave rise to a stationary, biphasic potential rendering the forearm initially positive (Pw) and subsequently negative (Nw) compared with the hand. A pair of electrodes located on each side of the wrist best detected the junctional potential, Pw-Nw, that developed across the partition. Here the hand and the forearm each, in effect, acted as a lead, connecting any points within the respective compartment to the voltage source. Thus, nearly the same potential difference appeared across the wrist regardless of the inter-electrode distance, allowing the detection of the voltage step in far-field derivation. Our data verify that not only positive but also negative peaks of scalp-recorded evoked responses could represent junctional potentials generated along the course of the conduction medium in the absence of fixed neural discharges.
mesh_terms: D000200:Action Potentials; D000328:Adult; D004594:Electrophysiology; D005542:Forearm / Q000502:physiology; D006225:Hand / Q000502:physiology; D006801:Humans; D008475:Median Nerve / Q000502:physiology*; D008875:Middle Aged; D012677:Sensation; D014953:Wrist / Q000502:physiology*