Most vocal learning species exhibit an early critical period during which their vocal control neural circuity can facilitate the acquisition of new vocalizations. Some taxa, most notably humans and parrots, retain this neurobehavioral plasticity throughout adulthood. Downregulation of the transcription factor FoxP2 in both songbird and parrot vocal control nuclei has been identified as a key expression pattern facilitating vocal learning. We hypothesize that open-ended vocal learning is vulnerable to cognitive decline and that this deterioration will be reflected in age-related changes in neural FoxP2 expression. We tested this hypothesis in the budgerigar (Melopsittacus undulatus), a small gregarious parrot in which adults converge on shared call types in response to shifts in group membership. We formed novel flocks of 4 previously unfamiliar males belonging to the same age class, either young adult (6 mo-1 yr) or older adult ( 3 yr), and then collected audio recordings over a 20-day learning period to assess vocal learning ability. Following behavioral recording, whole brains were extracted and immunohistochemistry was performed to measure FoxP2 protein expression in a parrot vocal learning center, the magnocellular nucleus of the medial striatum (MMSt), and its adjacent striatum. We find similarly downregulated FoxP2 expression and equivalent vocal plasticity and vocal convergence in young and older adults suggesting the maintenance of two components of open-ended learning into old age in the budgerigar. No relationship between individual variation in vocal learning measures and FoxP2 expression was detected.

Underlying data:

This dataset contains dataframes (.csv) of both vocal and neural data and the corresponding code used in analyzing this data in the form of an R script (.R):

1. Vocal_Brain_Correlation_03_09_2023_Final.r (R script consisting of code used for data analysis and statistics for age-related differences in FoxP2 expression.)
2. AgeLearn_Treatments_Master.csv (Dataframe containing experiment metadata such as bird identities and corresponding age class treatment. NAs in 'Hatch date' column indicate unknown hatch dates of birds obtained from a breeder who provided us with approximate ages.)
3. agg_dat.csv (Dataframe containing vocal learning measures for each bird and each recording block. Column names acoustic.area, acoustic.overlap, and acoustic.overlap.to.group correspond to vocal diversity, vocal plasticity, and vocal convergence, respectively. NAs in acoustic measurement columns indicate birds that produced too few calls for quantification purposes.)
4. Vocal_Brain_Corr_03_09_2023_Final.csv (Dataframe of FoxP2 MMSt/VSP expression ratios and vocal learning measures taken during the 5th recording block. NAs in acoustic measurement columns indicate birds that produced too few calls for quantification purposes.)
5. Vocal_Brain_Corr_03_09_2023_Final_WithAdditionalMMSTVSP.csv (Dataframe of FoxP2 % expression in MMSt, FoxP2 % expression in VSP, FoxP2 MMSt/VSP expression ratio, and vocal learning measures taken during the 5th recording block. NAs in acoustic measurement columns indicate birds that produced too few calls for quantification purposes.)
6. data_analysis.html (R code for data analysis & statistics for Bayesian models testing relationship between FoxP2 expression and vocal learning).