Fig. 2. Characterization of a high-threshold (HT) neuron and responses to von Frey filaments. (A ) Response of the neuron to brush and pinch. (B ) Responses to von Frey filaments. (C ) Digitized oscilloscope trace of action potentials during pinch. (D ) Drawing depicting the somatic field. The gray area is the region responding to pinch of cutaneous and deep tissue. The black dot represents the site of application of von Frey filaments. (E ) von Frey filament thresholds for nine HT neurons. (F ) Summary of the average peak increase in action potential rate produced by application of von Frey filaments to nine HT neurons. The bracket is the SD. (G ) The percent difference in the area under the curve (AUC) for two repeated stimulus–response functions in eight HT neurons. Rate = rate of action potentials in impulses per second; bin width = 2 s.