Sensory experiences in man evoked by intraneural electrical stimulation of intact cutaneous afferent fibers.

The response of slowly conducting myelinated and unmyelinated afferent units to natural types of cutaneous stimuli was recorded extracellularly with tungsten microelectrodes from intact human skin nerves. Seven fibers had characteristics of C-polymodal units (conduction velocity: 0.75-1.2 m/s) and two fit descriptions of myelinated high- threshold mechanoreceptors (conduction velocity of one: 19 m/s). Attempts were made to evoke a sensation in a subject by stimulating the impaled fascicles directly with electrical pulses of controlled amplitude, duration and frequency so as to try to correlate responsive properties of the sensory units and sensory experience. The subjective sensations evoked by natural stimuli to the skin surface were used as criteria for comparison.