Is neurogenesis in two songbird species related to their song sequence variability?

Neurogenesis takes part in the adult songbird brain and new neurons are integrated into the forebrain including defined areas involved in the control of song learning and production. It has been suggested that the new neurons in the song system might enable vocal variability. Here, we examined the basal levels of neurogenesis in two songbird species, zebra finch ( Taeniopygia guttata ) and Bengalese finch ( Lonchura striata var. domestica ), which do not learn new song elements as adults but differ in the level of song sequence variability. We found that Bengalese finches had less linear and stereotyped song sequence and a higher number of newborn cells in the neurogenic subventricular zone (SVZ) as well as the number of newly born neurons incorporated into the vocal nucleus HVC (used as a proper name) in comparison to zebra finches. Importantly, this vocal sequence variability in Bengalese finches correlated with the number of new neurons in the vocal nucleus HVC and more plastic song was associated with higher neuronal incorporation. In summary, our data support the hypothesis that newly generated neurons facilitate behavioural variability.