For each t-test applied, we report the associated p-value (the probability of observing the given result, or one more extreme, by chance if the null hypothesis is true), the value of the test statistic (t), and the degrees of freedom of the test (df). BG on song behavior in the zebra finch. We report that this manipulation abolishes social context-dependent changes in variability not only in harmonic stacks, but also in other types of syllables. However, song timing seems not to be modulated by this BG dopamine signal. Indeed, injections of a D1 antagonist in the BG altered neither song duration, nor the change of song duration with social context. Finally, D1 receptor activation in the BG was not necessary for the modulation of other features of song such as the number of introductory notes or motif L-Stepholidine repetitions. Together, our results suggest that activation of D1 receptors in the BG is necessary for the modulation of fine acoustic features of song with social context while it is not involved in the regulation of song timing and structure at a larger time scale. t-tests comparing the effect of social context in L-Stepholidine the presence or absence of the D1 antagonist. These t-tests were Bonferroni corrected for the number of comparisons made. For each t-test applied, we report the associated p-value (the probability of observing the given result, or one more extreme, by chance if the null hypothesis is true), the value of the test statistic (t), and the degrees of freedom of the test (df). A value of p<0.05 was considered as a significant difference. Results Activation of D1 receptors decreases spectral variability In a previous study, we showed LEG2 antibody that the activation of D1 receptors in Area X was responsible for the social context dependent modulation of the variability of the fundamental frequency of specific sub-syllabic elements called harmonic stacks (Leblois et al., 2010). To test whether the change in acoustic variability with social context through D1 receptor activation could be generalized to sub-syllabic elements that do not display the clear spectral structure of harmonic stacks, we made pairwise comparisons of renditions of a subset of each type of sub-syllabic element using the spectrogram cross-correlation method (see Methods, Nelson and Marler, 1994). The average cross-correlation coefficient among pairs of spectrograms of the renditions of this element was called the spectral similarity index. It allowed us to compare the acoustic variability in a set of renditions of each sub-syllabic element across different conditions. Fig. 2A displays the results of such analysis applied to the first element of syllable 6 in the song of bird #4 (whose motif and syllable partition is depicted in Fig. 1). In the baseline condition, the average spectral similarity between renditions of this note L-Stepholidine was higher when the bird sang in the presence of a female (solid black line, average cross-correlation of 0.65 0.09) than when he sang alone (dashed line, average cross-correlation of 0.55 0.13, p<0.001, t=?11, df=1752, note here that the number of degrees of freedom reflects the number of notes produced in each condition). To assess within this individual animal whether this example note exhibited different variability in the different social contexts and drug conditions, we compared spectral similarity values using a two-way ANOVA. This test revealed a significant interaction between the presence of a female and infusion of the D1 antagonist SCH23390 (F=4.24, df=1, p<0.05). Post-hoc analysis revealed that the syllable spectral similarity was increased in the presence of a female when saline was infused (0.55 0.1 alone versus 0.67 0.09 in the presence of a female, p<0.001, t=4.9, df=1614, Fig. 2A), but not during infusion of the D1 antagonist SCH 23390 into Region X (0.50 0.06 alone and 0.55 0.1 in the current presence of a lady, p=0.1, t=1.6, df=1619). Considering that variations in syllable size may influence the cross-correlation ideals and therefore skew the spectral similarity index assessed over many pairs, we replicated the evaluation of spectral similarity because of this sub-syllabic component by processing pair-wise cross-correlations after modifying syllable size through period warping (Anderson et al., 1996). Even though the spectral similarity was improved after period warping in every pharmacological circumstances, the variations in spectral similarity with sociable framework was still L-Stepholidine present at baseline (0.67 alone versus 0.74 in the current presence of a lady, p<0.001, t=?9.7, df=1752), abolished by SCH 23390 infusion in Region X (0.64 alone versus 0.66 in the current presence of a lady, p=0.2, t=?1.7, df=1642), and recovered following saline infusion (0.68 alone versus 0.76 in the current presence of a lady, p<0.001, t=5.0, df=1714). Open up in another window Shape 2 Infusion from the D1 receptor antagonist SCH23390 into Region X abolishes variations in spectral similarity because of social framework: an exampleA) Distributions from the spectral L-Stepholidine similarity index among pairs of renditions.