Fig. 5.

Quantification of temporal properties of HVC premotor activity during duetting. a Time lags of maximum cross-covariance between male and female neural signals (root-mean-square envelopes) during 179 duet bouts produced by three bird pairs were clustered at approximately 250 ms. The green lines indicate interquartile ranges of lags and cross-covariance coefficients, and their intersection is at the medians of the distributions. b The covariance of neural signals was strongly correlated with the covariance of vocal signals. The dashed green line represents the regression line. n = 56 duet bouts of three bird pairs. c The degree of overlap in neural activity was strongly correlated with the degree of syllable overlap. The dashed green line represents the regression line. n = 47 overlaps produced by two bird pairs. d During emission of duet-initiating syllables, oscillation frequencies of the male and female neural signals were significantly higher (p < 0.005, Mann–Whitney U test) than during emission of alternating syllables during duetting. Labeling of boxplots as in Fig. 3c