Figure 1
Summary of song brain regions of interest. (A) Schematic representation of brain regions focused upon and their interconnections. Microlesions target HVC and produce vocal deficits with recovery dependent on sensorimotor learning (deafened birds do not recover14). Red arrows represent the anterior forebrain pathway (AFP), a cortico-basal ganglia-thalamic circuit critical for vocal learning and inducing vocal variability through adulthood. Green arrows represent vocal motor pathways. Dashed regions indicate approximate x,y locations of regions not visible in panel B. (B) Is a representative darkfield image used to identify sections with regions of interest and to define their borders for superimposing on images obtained later via confocal microscopy. This image was used to produce the camera lucida-type tracing in Panel A. Note the distinct nuclear organization of song regions contrasts with laminated mammalian cortex and allows targeting for lesioning, dissection, and other manipulation. Rostral is approximately right, dorsal up, and bars = 1 mm. Abbreviations: HVC (proper name), lMAN (lateral magnocellular nucleus of the anterior nidopallium), RA (robust nucleus of the arcopallium), Area X (Area X of striatum, note that songbird striatum also contains pallidal projection neurons and interneurons that anatomically distinguish it from mammalian striatum that separates these features20).
