Figure 6.

A, Polar plots showing the angular shift in the preferred firing direction between the standard 1 and rotation sessions for control (left) and IPN-lesioned (right) rats. Each dot on the periphery represents the magnitude of the shift in the preferred firing direction for one HD cell. For the control group, the gray circles represent the shift values for animals included in the present study, and the black circles represent shift values from previous studies. For the IPN-lesioned group, the white circles represent the shift values for electrolytic lesioned animals, and the black circles represent the shift values from neurotoxic lesioned rats. The black arrow denotes the observed mean vector angle, and the broken line denotes the expected 90° vector if the angular shift values are perfectly predicted by the cue card. Mean vector length values (r) are indicated within the plot and are depicted by the length of the solid arrow. The length of r represents the variability in the shift angles for the group, with values of 1.0 indicating an absence of variability. Asterisks mark r values that tested significantly nonrandom as indicated by the Rayleigh test (**p < 0.01; ***p < 0.001). For both groups, most cells exhibited a change in the preferred firing direction after the cue card rotation. Note that, although the variability in the shifts is much greater in IPN-lesioned rats, the shifts were distributed nonrandomly for both groups. B, Polar plots showing the angular shift in the preferred firing direction between the standard 1 and standard 2 sessions for control (left) and IPN-lesioned (right) rats. The 0° point indicates the expected vector if the shift values are perfectly predicted by the cue card rotation. Again, the shifts for IPN-lesioned rats are more variable but are distributed nonrandomly.