Imc signals stimulus competition with greater precision, and earlier than OTid. A, Distributions of biases of competitor response profiles of OTid neurons (blue; n = 36 neurons with correlated competitor response profiles; median = −0.83; p = 0.62; sign test against 0 and Imc neurons (red; data reproduced from Fig. 4B; n = 66; median = −0.52). No significant difference between Imc and OTid medians (p = 1.0, sign test after Holm–Bonferroni correction for multiple comparisons). B, Proportions of switch-like (S), gradual (G), and uncorrelated (U) competitor response profiles measured in Imc (stacked bar on left; n = 78 neurons at which competitor response profiles where measured) and OTid (middle bar; n= 53 neurons at which competitor response profiles were measured). Previously published OTid proportions (n = 169 neurons at which competitor response profiles were measured; data adapted from Mysore et al., 2011) are also shown for completeness (right bar; unfilled). * (n.s.): χ² statistic = 5.21, p = 0.02 (p = 1.0), χ² test between Imc and OTid proportions measured here followed by Holm–Bonferroni correction for multiple comparisons. C, Comparison of d-prime (Materials and Methods) computed from pooled competitor response profile responses measured in OTid (blue) versus Imc (red). *p = 0.01, permutation test (Materials and Methods). Inset, Schematic of pooled competitor response profile responses across neurons illustrating d-prime computation across the selection boundary (vertical gray line). D, Pooled instantaneous firing rates (IFRs) of OTid neurons with gradual competitor response profiles in response to S1 alone (gray) or paired S1 and S2 (green), binned into five relative strength bins (columns). E, Millisecond-by-millisecond running ANOVA to determine time to suppression (vertical dashed line): the first instant at which responses to paired S1 and S2 diverge significantly from responses to S1 alone (Materials and Methods). OTid responses never diverge significantly for the first relative strength bin (S2-S1 = −7 °/s; left-most panel). F, G, Same as E and F, but for OTid neurons with switch-like competitor response profiles (magenta data); OTid responses never diverge significantly for the first relative strength bin (S2-S1 = −7 °/s; left-most column). H, Population summary: Scatter plot of time to suppression for OTid neurons versus Imc neurons for the different relative strength bins (i.e., scatter plot of green numbers in D versus magenta numbers in F). Dots, (Imc, OTid) time to suppression pairs for the different relative strength bins; magenta data, switch-like competitor response profiles; green data, gradual competitor response profiles; progressively larger dots indicate increasing relative strength (S2-S1). For plotting purposes, time to suppression values corresponding to cases in which the responses to paired S1 and S2 never diverged from those to S1 alone, are coded as 450 ms. Dashed line: line of equality. Inset, Boxplot of differences between OTid and Imc time to suppression values; *p = 0.02, sign test against 0.