Fig. 10. Representative normalized and rotated circular histograms of directional activity for all three sub-classes of receptor (A–C). The receptive field (RF) and stimulus directions, including the direction of maximum activity (MAX) are depicted to the right (a1–d1). (A) Receptor 17-1 was representative of the Pacinian-like (PC-like) population. This receptor was moderately directionally tuned by the Rayleigh statistic but showed low scores for the tuning ratio (TR) and tuning index (TI) (see Table 1). (B) Receptor 7-16 was the only slowly adapting response and was strongly directionally tuned. (C) Receptor 13-1 was representative of the rapidly adapting-unknown (RA-X) population. This receptor was strongly directional and responses were inverted when the stimulator was rotated 180° (c2). (D) The most highly directionally tuned receptor found in the study. This receptor scored high on all measures of directionality and responses were inverted when the stimulator was rotated 180° (d2). Scale bars, 1 mm.