Morphology of Golgi‐impregnated neurons in hyperstriatum ventralis, pars caudalis in adult male and female canaries

Abstract

Golgi-impregnated neurons in the song control nucleus hyperstriatum ventralis, pars caudalis (HVc) in male and female canaries (Serinus canarius) have been divided into classes, primarily on the basis of interneuronal variability in spine density and dendritic branching pattern. At least four neuronal classes are found in HVc: aspinous neurons and three classes of spiny neurons. The "furry" dendrite (FD) cell class consists of neurons with long dendrites that are densely packed with spines. Their cell bodies are between 10 and 15 microns in diameter. Neurons of the thick dendrite (TD) cell class also have long dendrites but only about half as many spines along their dendritic branches. Their cell bodies are between 12 and 18 microns in diameter. Neurons of the short dendrite (SD) cell class are characterized by a low spin density, very thin dendrites, and a small dendritic field. Their cell bodies are between 9 and 13 microns in diameter. The TD class can be divided into two subclasses on the basis of the shape of the dendritic field. Principal component factor analysis and cluster analysis provide objective support for this classification scheme. Neurons of subclass TD2 are sexually dimorphic. Neurons from males have dendritic trees that are about 70% larger and have 40% more dendritic endings than do neurons from females. There may also be small sex differences in dendritic morphology in the SD class and in the remainder of the TD class. There are clearly no sex differences in the dendritic morphology of neurons from the FD class. The direct pathway which is believed responsible for dimorphic song production in canaries is from HVc to nucleus robustus archistriatalis (RA) and then to the motor neurons which control the avian vocal organ. It is surprising that the most striking dimorphism in the present data occurs in neurons which, on morphological grounds, are unlikely to project to RA.

Sodium‐ and calcium‐dependent conductances of neurones in the zebra finch hyperstriatum ventrale pars caudale in vitro.

“…relatively large soma size, large dendritic fields and many spines on the dendrites. The HVc neurones stained in this study also correspond to the type of thick dendrite cell classified in Golgi-impregnated HVc neurones of the canary (Nixdorf, Davis & DeVoogd, 1989).…”

Divergent and parallel development in volume sizes of telencephalic song nuclei in and female zebra finches

“…function for females, because only small sex differences in neuronal structure could be detected in Golgi-stained material (Nixdorf et al, 1989). The sex difference in volume of HVC in the canary brain was also much smaller compared to the differences observed in the zebra finch brain .…”

Song and the song control pathway in the brain can develop independently of exposure to song in the sedge warbler

“…Under high magni cation (´1250), neurons for determination of dendritic spine density were selected. We considered only spiny neurons (Nixdorf et al 1989;Airey et al 2000b) and measured up to three dendrites per neuron, by projecting them with a camera lucida. In addition, spine density was calculated at 20 m m intervals from the soma to the tip of the dendrites.…”