Figure 4.

Illustration of the analysis used to compare changes of SS activity with saccade amplitude during adaptation and preadaptation. A, SS activity of a resampled adaptation data subset (112 samples from 274 total). C, Preadaptation data. Colorized SS activity ordered from top according to binned trial number (A) or binned amplitude (C); the right panels in A and C show associated changes in saccade amplitude. B, R² of the relationship between SS activity of the adaptation subset in A and bin number; the gray curve shows another adaptation subset with no significant interval. D, R² of the relationship between SS activity in C (left panel) and binned amplitudes in C (right panel). E, Average spike rate versus average saccade amplitude for the resampled subset of adaptation data in A (blue dots; p < 0.05; r = −0.54; slope, −8.23) and the preadaptation data in C (red dots; p < 0.05; r = 0.60; slope, 3.51 sp · s⁻¹ · deg⁻¹). The dashed lines in the right panels of A and C show that the adapt and pre data have the same amplitude ranges. The smallest adapt averages (black dots) never go <10° because it is attributable to saccades lying mostly between 11 and 12°. The black dots are the same amplitude averages that appear in E. F, Slopes of the average spike rate versus amplitude relationships for each of the 50 resampled adaptation subsets and the associated preadaptation data connected by gray lines (black line from data in E). In seven resampled adaptation subsets, there was no significant interval, so the adaptation slope is plotted as 0 (right point of dashed line). Note that the slopes for the preadaptation regressions differed because the analysis interval varied (for details, see Materials and Methods). For 40 of the 50 subsets, the slopes of preadaptation and adaptation regressions were significantly different. The slopes obtained from adapted saccade data were significantly smaller than those from preadaptation saccade data (χ² test; p < 0.05; mean adapt − pre slopes, −8.27).