PV mRNA expression ratios measured from the in situ hybridizations in avian species.

<p>(A) PV expression ratio of arcopallium song nuclei and adjacent intermediate arcopallium (iA) for vocal learners, and ciA and adjacent intermediate arcopallium (iA) for non-learners. Also quantified is a control gene, ER81. The line across the graph is at ratio = 1, which means both areas equally express the gene. (B) PV expression ratio of SSp and nXllts, and another control gene GDNF family receptor alpha 1. Stars (*) inside bars indicate significant difference between two areas (A. arcopallium song nuclei or ciA and surrounding iA. B. SSp and nXllts) within each species using paired <i>t</i>-test on raw values. Number symbol (#) above bars indicates a significant difference between vocal learners and non-learners using unpaired <i>t</i>-test on ratios. ZF, zebra finch; BG, budgerigar; H, hummingbird; Hl, humming bird lateral part of nXllts; Hm, hummingbird medial part of nXllts; D, dove; Q, quail. *p<0.05, **p<0.001.