Nest of Origin Predicts Adult Neuron Addition Rates in the Vocal Control System of the Zebra Finch

Abstract

Neurogenesis and neuronal replacement in adulthood represent dramatic forms of plasticity that might serve as a substrate for behavioral flexibility. In songbirds, neurons are continually replaced in HVC (used as a proper name), a pre-motor region necessary for the production of learned vocalizations. There are large individual differences in HVC neuron addition. Some of this variation is probably due to individual differences in adult experience; however, it is also possible that heritability or experience early in development constrains the levels of adult neuron addition. As a step toward addressing the latter two possibilities, we explored the extent to which nest of origin predicts rates of HVC neuron addition in adult male zebra finches. One month after injections of [³H]-thymidine to mark dividing cells, neuron addition in HVC was found to co-vary among birds that had been nest mates, even when they were housed in different cages as adults. We also tested whether nest mate co-variation might be due to shared adult auditory experience by measuring neuron addition in nest mate pairs after one member was deafened. There were significant differences in neuron addition between hearing and deaf birds but nest mate relationships persisted. These results suggest that variation in genotype and/or early pre- or postnatal experience can account for a large fraction of adult variation in rates of neuron addition. These results also suggest that a major constraint on neurogenesis and the capacity to adjust rates of neuron addition in response to adult auditory experience is established early in development.

Adult Neurogenesis in the Songbird: Region-Specific Contributions of New Neurons to Behavioral Plasticity and Stability

“…This supports the idea that new neurons in HVC may contribute to the integrity or maintenance of the motor behavior, rather than contributing to plasticity, drift, and change in the motor structure. In this study, which is consistent with others [Hurley et al, 2008], there was no overall group difference in new HVC-RA neurons between deafened and hearing birds, suggesting that factors related to auditory deprivation or the act of deafening, such as stress, did not alter the number of new neurons in HVC. The result also could not be explained by individual differences in singing rate [Pytte et al, 2012].…”

The relationship of neurogenesis and growth of brain regions to song learning

“…Indeed, in more recent work we found a small but significant increase in HVC neuron incorporation in deafened birds compared to their hearing cage mates (Fig. 7; Hurley et al, 2008). At present, the safest conclusion one can draw from this work is that hearing may be important in some contexts (as was found in juveniles with ts nerve cuts), however, complete absence of normal auditory function, by itself, plays a minor, if any, role in the regulation of HVC growth or neuronal replacement.…”

Sex-Specific Modulation of Cell Proliferation by Socially Relevant Stimuli in the Adult Green Treefrog Brain <i>(Hyla cinerea)</i>

“…Thus, these results indicate that hearing a conspecific chorus induces cell proliferation and/or survival in the POA regardless of the behavioral output, and that calling in response to the chorus might enhance this effect on cell proliferation. In songbirds, singing has been shown to increase neuron proliferation and survival in the high vocal center (HVC) [Li et al, 2000;Alvarez-Borda and Nottebohm, 2002], but removing auditory feedback by deafening caused zebra finches to have decreased new HVC cells in one study [Wang et al, 1999] but increased cell addition in another study [Hurley et al, 2008]. Because deafened birds engage in singing behavior, albeit altered, it is difficult to separate the factors affecting cell proliferation and/or survival in that system.…”