Fig. 2

Schematic of core and shell systems for vocal learning in a parrot brain [83]. Red regions: core song system (similar to songbirds); yellow regions in pallium/cortex: shell song system (unique to parrots). Solid black arrow: shell system posterior vocal motor pathway; solid white arrows: shell system anterior vocal motor pathway; dashed arrows: connections between core and shell systems. For simplicity several connections are not shown, including connections among core system regions. Also not shown is the direct projection from AAC (central nucleus of the anterior arcopallium) core region to the brainstem’s hypoglossal nucleus (labelled XII in the figure’s hindbrain region): this projection is analogous to the direct projection in songbirds from the forebrain primary motor region RA (robust nucleus of the arcopallium) to XII. (See [83] for definitions of other acronyms.)