Differences in the complexity of song tutoring cause differences in the amount learned and in dendritic spine density in a songbird telencephalic song control nucleus

In our search for relations between vocal learning and neuron structure in the song control nuclei of songbird forebrains, we tested whether different ial experience that leads to differences in adult song repertoire would aff ect dendritic spine density in HVc (also called high vocal center) and RA ( robustus archistriatalis). We tape-tutored juvenile Eastern marsh wrens (Ci stothorus palustris) with either 5 or 45 song types. As adults, the small r epertoire group had learned mostly 5 or 6 song types, and the large reperto ire group had learned 36 to 47. Wrens that learned the large song repertoir es had a greater dendritic spine density for the most spiny neurons present in HVc (mean difference, 36%), but not in RA. Recent physiological evidenc e describes HVc as a premotor area coding syllables, motifs, and higher-ord er song patterns, and our data now clearly reveal that differences in the s ize of the song repertoire that is experienced lead to differences both in song learning and in the density of dendritic spines in HVc. In the forebra in song nuclei of these songbirds, as in some other vertebrate systems, dif ferences in learning and performance are associated with differences in syn aptic anatomy specifically in the region that organizes the learned pattern . (C) 2000 Academic Press.