Far-field somatosensory evoked potentials in response to selective stimulation of small diameter myelinated fibers in the cat.

Five far-field components were identified preceding the cortical wave in response to the stimulation of the A beta fibers of the sural nerve. When A delta activity was also included in the afferent volley, a second cortical wave and additional far-field potentials were recorded. Upon blocking the A beta fiber activity and thus isolating the peripheral input to A delta fibers alone, the initial cortical wave and the far-field potentials preceding it disappeared completely, leaving the A delta evoked potentials intact.