PMC

Comparison of HVC somatic area (A) and neuronal density (B) across hemispheres in birds infused with vehicle or the highest dose of BDNF. Bars are group means ± SEM; numbers inside bars indicate number of birds in each group.

Comparison of RA somatic area (A) and neuronal density (B) across hemispheres in birds infused with saline, TrkB-Fc alone, TrkC-Fc alone, or TrkB&C-Fc. Bars are group means ± SEM; numbers inside bars indicate number of birds in each group. *p = 0.059 (Tukey's HSD), comparison between ipsilateral and contralateral side.

Dark-field photomicrograph (A) and quantitative analysis (B) of TrkB mRNA expression in RA in the different treatment groups. Arrows delineate the borders of RA. Data in B are expressed as a ratio of the grain density within the song nucleus versus the surrounding pallial region. Bars are group means ± SEM, and each point represents one bird.

Comparison of RA somatic area (A), neuronal density (B), and volume (C) in birds infused with one of four concentrations of BDNF near RA on one side of the brain. Bars are group means ± SEM; numbers inside bars indicate number of birds in each group (each number refers also to adjoining bar from opposite hemisphere). Value of p from Tukey's HSD, comparison between ipsilateral and contralateral side. Symbols above bars represent differences between ipsilateral and contralateral sides (Tukey's HSD); *p < 0.001; ^†p = 0.058.

Dark-field photomicrographs of in situ hybridization showing BDNF mRNA expression in HVC (A) and RA (B) of birds in the four treatment groups. Arrows delineate the borders of the song nuclei. Boxes indicate area from which pallial measurements were taken. Scale bars, 300 μm. Quantitative analysis of BDNF mRNA expression in HVC (C) and RA (D). Data are expressed as a ratio of the grain density within the song nucleus versus the surrounding pallial region. Bars are group means ± SEM, and each point represents one bird. Letters above bars represent statistically different groups (Tukey's HSD p < 0.05).