Fig. 7. Receptor responses to indentation velocity related to the speed at which the mole touches its nose to the ground (46.2 mm s^–1). (A) Lowest indentation velocity required to elicit a 1:1 for RA units (Left). A number of cells were most activated near the behaviorally relevant speed. The same graph is divided by sub-class on right. (B) Lowest velocity required to elicit any response. (Left) Most cells responded at less than 1:1 to the lower velocities. (Right) The same graph divided by sub-class. The PC-like units tended to be responsive at the lowest velocity and as such were more sensitive than the RA-X group. (C) Stimulus response relations for two cells that appeared to code indentation velocity (Left). As indentation velocity increased, the average interval frequency increased. Both cells appeared to be tuned near the behaviorally relevant velocity of 46.2 mm s^–1. (Right) Responses during the ramp indentation. PC-like, Pacinian-like; RA-X, rapidly adapting-unknown; RA-IC, rapidly adapting-incomplete classification.