Figure 1.

Location of song system components in the male zebra finch. (A) μCT-based volume rendering of the zebra finch skeleton. Boxed section shown enlarged in C. (B) Virtual sagittal section through a 3D high-field MRI dataset of the male zebra finch head. Visible are three nuclei of the song system: HVC (used as a proper name) and the robust nucleus of the arcopallium (RA) that both belong to the descending motor pathway, and the lateral portion of the magnocellular nucleus of the anterior nidopallium (LMAN), which belongs to the anterior forebrain pathway. Dotted lines indicate the virtual sections shown in E and F. (C) Virtual sagittal section through a 3D MRI dataset showing that the syrinx is located at the bifurcation of the trachea into the bilateral primary bronchi, close to the heart (red shaded outline) and lungs (green shaded outline). Note the dark seeds in the crop. The asterisks indicate intercostal muscles. (D) μCT-based volume rendering showing the hyoid bone (yellow) and larynx (blue), which are upper vocal tract modulators important in the filtering of sound properties [38,40]. (E,F) Virtual transversal sections through a 3D MRI dataset of the head as indicated in (B) showing the tongue, larynx, trachea (blue) and hyoid (yellow dotted line). Scale bars: 10 mm.