Responses of two PBil–PC neurons (one inA, the other in B) to innocuous (near the pain threshold) and noxious stimuli. Thermal (A1,B1) and mechanical (A2,B2) stimuli were applied for 24 secbetween the two arrows. Note that, in each case, the weak response to innocuous stimuli and the heavy and tonic response to noxious stimuli was followed by marked (A) and moderate (B) afterdischarges.