Journal of Neuroscience, Vol 1, 1279-1288, Copyright © 1981 by Society for Neuroscience
Bilateral organization of the vocal control pathway in the budgerigar, Melopsittacus undulatus
JA Paton, KR Manogue and F Nottebohm
Anatomical and electrophysiological methods were used to map the vocal
control nuclei of the budgerigar, Melopsittacus undulatus. Beginning with
the motor nucleus of the syrinx, nuclei were located using antidromic
stimulation and then injected with horseradish peroxidase (HRP).
Retrogradely transported HRP labeled afferents to the injected nucleus.
This procedure was repeated at successively higher levels along the vocal
pathway. Connections found using this strategy then were confirmed using
anterograde transport of HRP and/or tritiated proline and orthodromic
electrical stimulation. We found that the primary vocal control pathway
consisted of (1) the motor nucleus innervating the trachea and syrinx,
nXIIts; (2) an archistriatal nucleus, RA; and (3) a neostriatal nucleus,
"HVc." These nuclei correspond to similar, possibly homologous, nuclei in
the vocal control pathway of the canary (Nottebohm, F., T. M. Stokes, and
C. M. Leonard (1976) J. Comp. Neurol. 165: 457-486) but, because of
differences in gross brain morphology, are displaced considerably in
absolute position. Furthermore, the projection from RA to the motor nucleus
is bilateral in the budgerigar, whereas the same connection is strictly
ipsilateral in the canary. The projection of the motor nucleus to muscles
of the vocal organ is also bilateral in the budgerigar (Manogue, K. R., and
F. Nottebohm (1981) J. Compl. Neurol., in press) but ipsilateral in the
canary. the possible significance of these species differences for
lateralization of motor control is discussed.