Best-fit intermediate reference frames for 63 neurons. A, The population mean PRESS values of best fits for all 63 neurons combined, for target and final gaze positions plotted in the intermediate reference frames at α intervals of 0.1 on the continuum between head and eye frames. The overall best-fit intermediate frame across all continua is indicated (□). B, C, For individual neurons, the best-fit intermediate reference frames are plotted in B if the best fit occurs for target-position intermediate frame, and in C if it occurs for final-gaze intermediate frame, from across all continuums between the four canonical reference frames: s, h, e, and v. Each neuron's best-fit intermediate frame is indicated by ○, a larger diameter circle indicating more than one neuron at the same frame. Overall best-fit for neuron population, as in A, is indicated (□). Confidence intervals along the continua correspond to intermediate frames that could not be excluded as the best fit (did not have a significantly greater PRESS than the best-fit frame at the p = 0.05 level), and are indicated by the gray zones.