Premium
Morphology of axonal projections from the high vocal center to vocal motor cortex in songbirds
Author(s) -
Yip Zhiqi C.,
MillerSims Vanessa C.,
Bottjer Sarah W.
Publication year - 2012
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.23084
Subject(s) - neuroscience , biology , motor cortex , sensory system , cortex (anatomy) , nucleus , axon , anatomy , hindbrain , central pattern generator , central nervous system , physics , stimulation , rhythm , acoustics
Only birds that learn complex vocalizations have telencephalic brain regions that control vocal learning and production, including HVC (high vocal center), a cortical nucleus that encodes vocal motor output in adult songbirds. HVC projects to RA (robust nucleus of the arcopallium), a nucleus in motor cortex that in turn projects topographically onto hindbrain neurons innervating vocal muscles. Individual neurons projecting from HVC to RA (HVC RA ) fire sparsely to drive RA activity during song production. To advance understanding of how individual HVC neurons encode production of learned vocalizations, we reconstructed single HVC axons innervating RA in adult male zebra finches. Individual HVC RA axons were not topographically organized within RA: 1) axon arbors of HVC cell bodies located near each other sent branches to different subregions of RA, and 2) branches of single HVC axons terminated in different locations within RA. HVC RA axons also had a simple, sparse morphology, suggesting that a single HVC neuron activates a limited population of postsynaptic RA neurons. These morphological data are consistent with previous work showing that single HVC RA neurons burst sparsely for a brief period of time during the production of a song, indicating that ensembles of HVC RA neurons fire simultaneously to drive small temporal segments of song behavior. We also examined the morphology of axons projecting from HVC to RA cup, a region surrounding RA that receives input from auditory cortex. Axons projecting to RA cup also sent some branches into RA, suggesting direct integration between the sensory and motor circuits for song control. J. Comp. Neurol. 520:2742–2756, 2012. © 2012 Wiley Periodicals, Inc.