title: The zebra finch paradox: song is little changed, but number of neurons doubles.
abstract: New neurons are added to the high vocal center (HVC) of adult males in seasonally breeding songbirds such as the canary (Serinus canaria) that learns new songs in adulthood, and the song sparrow (Melospiza melodia) that does not. In both cases, the new neurons numerically replace others that have died, resulting in a seasonal fluctuation in HVC volume and neuron number. Peaks in neuronal replacement in both species occur in the fall when breeding is over and song is variable. New neurons are added, too, to the HVC of zebra finches (Taeniopygia guttata) that do not learn new songs in adulthood and whose song remains stereotyped throughout the year. Here, we show that, in contrast to the observations in seasonal songbirds, neurons added to the zebra finch HVC are not part of a replacement process. Rather, they lead to a doubling in the number of neurons that project from HVC to the robust nucleus of the arcopallium (RA). As this happens, HVC volume remains constant and the packing density of its neurons increases. The HVC-RA neurons are part of a descending pathway that carries the pattern of learned song; some HVC-RA neurons are also responsive to song playback. The addition of HVC-RA neurons happens in zebra finches housed singly, but becomes more acute if the birds are housed communally. We speculate that new neurons added to the adult HVC may help with the production or perception of learned song, or both.
authors.affiliation: Laboratory of Animal Behavior, The Rockefeller University, New York, New York 10065, USA. clareawalton@hotmail.com
authors.forename: Clare
authors.initials: C
authors.lastname: Walton
authors.forename: Eben
authors.initials: E
authors.lastname: Pariser
authors.forename: Fernando
authors.initials: F
authors.lastname: Nottebohm
mesh_terms: D000367:Age Factors; D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D002452:Cell Count; D053144:Cell Nucleus Shape; D002772:Cholera Toxin / Q000378:metabolism; D051959:ELAV Proteins / Q000378:metabolism; D046369:Finches / Q000033:anatomy & histology* / Q000502:physiology*; D005786:Gene Expression Regulation; D053400:High Vocal Center / Q000166:cytology*; D016014:Linear Models; D008297:Male; D008959:Models, Neurological; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009434:Neural Pathways / Q000502:physiology; D055495:Neurogenesis / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D012931:Social Environment; D013997:Time Factors; D014828:Vocalization, Animal / Q000502:physiology*
chemical_list: D051959:ELAV Proteins; D009419:Nerve Tissue Proteins; D002772:Cholera Toxin; D001973:Bromodeoxyuridine