Fig 20. Schematic drawing summarizing the findings of this and other studies.

Drawn are sections in the coronal plane through a budgerigar brain, showing the core (red shapes) and surrounding shell (yellow shapes) song nuclei. Arrows show descending core-to-core pathways (orange), descending shell-to-shell pathways (purple), descending connections to MMSt (dark blue), ascending bilateral song pathways (blue), and shell and core interactions within the same song nucleus (green). The connections are based on findings in this and prior studies of Durand et al. [34], Brauth et al. [31], Striedter [32], and Paton et al. [33].