title: Core and Shell Song Systems Unique to the Parrot Brain.
abstract: The ability to imitate complex sounds is rare, and among birds has been found only in parrots, songbirds, and hummingbirds. Parrots exhibit the most advanced vocal mimicry among non-human animals. A few studies have noted differences in connectivity, brain position and shape in the vocal learning systems of parrots relative to songbirds and hummingbirds. However, only one parrot species, the budgerigar, has been examined and no differences in the presence of song system structures were found with other avian vocal learners. Motivated by questions of whether there are important differences in the vocal systems of parrots relative to other vocal learners, we used specialized constitutive gene expression, singing-driven gene expression, and neural connectivity tracing experiments to further characterize the song system of budgerigars and/or other parrots. We found that the parrot brain uniquely contains a song system within a song system. The parrot "core" song system is similar to the song systems of songbirds and hummingbirds, whereas the "shell" song system is unique to parrots. The core with only rudimentary shell regions were found in the New Zealand kea, representing one of the only living species at a basal divergence with all other parrots, implying that parrots evolved vocal learning systems at least 29 million years ago. Relative size differences in the core and shell regions occur among species, which we suggest could be related to species differences in vocal and cognitive abilities.
authors.affiliation: Department of Neurobiology, Duke University Medical Center, Durham, NC, United States of America; Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America.
authors.forename: Mukta
authors.initials: M
authors.lastname: Chakraborty
authors.affiliation: Department of Biology, University of Copenhagen, Copenhagen, Denmark; Research Laboratory for Stereology and Neuroscience, Bispebjerg University Hospital, Copenhagen, Denmark.
authors.forename: Solveig
authors.initials: S
authors.lastname: Walløe
authors.affiliation: Danish National Police, National Centre of Forensic Services, Vanloese, Denmark.
authors.forename: Signe
authors.initials: S
authors.lastname: Nedergaard
authors.affiliation: Department of Neurobiology, Duke University Medical Center, Durham, NC, United States of America.
authors.forename: Emma E
authors.initials: EE
authors.lastname: Fridel
authors.affiliation: Department of Biology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Torben
authors.initials: T
authors.lastname: Dabelsteen
authors.affiliation: Research Laboratory for Stereology and Neuroscience, Bispebjerg University Hospital, Copenhagen, Denmark.
authors.forename: Bente
authors.initials: B
authors.lastname: Pakkenberg
authors.affiliation: Copenhagen Zoo, Frederiksberg, Denmark.
authors.forename: Mads F
authors.initials: MF
authors.lastname: Bertelsen
authors.affiliation: Dutch Research Institute of Avian and Exotic Animals, Veldhoven, The Netherlands.
authors.forename: Gerry M
authors.initials: GM
authors.lastname: Dorrestein
authors.affiliation: University of Maryland, College Park, MA, United States of America.
authors.forename: Steven E
authors.initials: SE
authors.lastname: Brauth
authors.affiliation: LaGuardia Community College, New York, NY, United States of America.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Durand
authors.affiliation: Department of Neurobiology, Duke University Medical Center, Durham, NC, United States of America; Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America.
authors.forename: Erich D
authors.initials: ED
authors.lastname: Jarvis
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology*; D006801:Humans; D007858:Learning; D009146:Music; D009520:New Zealand; D010311:Parrots / Q000502:physiology*; D014828:Vocalization, Animal / Q000502:physiology*