title: Adult Neurogenesis Leads to the Functional Reconstruction of a Telencephalic Neural Circuit.
abstract: Seasonally breeding songbirds exhibit pronounced annual changes in song behavior, and in the morphology and physiology of the telencephalic neural circuit underlying production of learned song. Each breeding season, new adult-born neurons are added to the pallial nucleus HVC in response to seasonal changes in steroid hormone levels, and send long axonal projections to their target nucleus, the robust nucleus of the arcopallium (RA). We investigated the role that adult neurogenesis plays in the seasonal reconstruction of this circuit. We labeled newborn HVC neurons with BrdU, and RA-projecting HVC neurons (HVCRA) with retrograde tracer injected in RA of adult male white-crowned sparrows (Zonotrichia leucophrys gambelii) in breeding or nonbreeding conditions. We found that there were many more HVCRA neurons in breeding than nonbreeding birds. Furthermore, we observed that more newborn HVC neurons were back-filled by the tracer in breeding animals. Behaviorally, song structure degraded as the HVC-RA circuit degenerated, and recovered as the circuit regenerated, in close correlation with the number of new HVCRA neurons. These results support the hypothesis that the HVC-RA circuit degenerates in nonbreeding birds, and that newborn neurons reconstruct the circuit in breeding birds, leading to functional recovery of song behavior.
  
  
  
  We investigated the role that adult neurogenesis plays in the seasonal reconstruction of a telencephalic neural circuit that controls song behavior in white-crowned sparrows. We showed that nonbreeding birds had a 36%-49% reduction in the number of projection neurons compared with breeding birds, and the regeneration of the circuit in the breeding season is due to the integration of adult-born projection neurons. Additionally, song structure degraded as the circuit degenerated and recovered as the circuit regenerated, in close correlation with new projection neuron number. This study demonstrates that steroid hormones can help reestablish functional neuronal circuits following degeneration in the adult brain and shows non-injury-induced degeneration and reconstruction of a neural circuit critical for producing a learned behavior.
authors: Department of Biological Sciences, Minnesota State University, Mankato, Minnesota 56001, rachel.cohen@mnsu.edu.
authors: Rachel E
authors: 0000-0001-8368-6885
authors: RE
authors: Cohen
authors: Graduate Program in Neuroscience and Behavior, University of Massachusetts, Amherst, Massachusetts 01003, CAPES Foundation, Ministry of Education of Brazil, Brasilia DF 70040-020, Brazil, and.
authors: Matheus
authors: 0000-0003-3536-3736
authors: M
authors: Macedo-Lima
authors: Departments of Psychology and.
authors: Kimberly E
authors: 0000-0002-8858-3532
authors: KE
authors: Miller
authors: Departments of Psychology and Biology, University of Washington, Seattle, Washington 98195.
authors: Eliot A
authors: 0000-0002-1920-923X
authors: EA
authors: Brenowitz
mesh_terms: D000818:Animals; D001947:Breeding; D001973:Bromodeoxyuridine / Q000378:metabolism; D002452:Cell Count; D008297:Male; D009415:Nerve Net / Q000502:physiology*; D055495:Neurogenesis / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D017440:Photoperiod; D046370:Sparrows; D013223:Statistics as Topic; D013239:Stereotyped Behavior / Q000502:physiology; D013687:Telencephalon / Q000166:cytology*; D013739:Testosterone / Q000097:blood; D014828:Vocalization, Animal / Q000502:physiology*
chemical_list: D013739:Testosterone; D010751:Phosphopyruvate Hydratase; D001973:Bromodeoxyuridine
keywords: HVC; adult neurogenesis; plasticity; regeneration; songbird; testosterone