Understanding the patterns of neuronal activity due to vocalizations in different species

Abstract

Songbirds within the Estrildidae family exhibit wide variation in vocal complexity, from the highly stereotyped songs of the zebra finch to the flexible and complex sequences of the bengalese finch, and the harmonic stack-based vocalizations of the owl finch. Despite such acoustic divergence, song production across these species is mediated by conserved neural circuit that includes the premotor nucleus HVC and the robust nucleus of the arcopallium (RA). This study examines how interspecies variation in song complexity is reflected in neural activation patterns and song control nucleus properties. Using immediate early genes (IEGs) as markers of neuronal activity, we tested the hypothesis that species with more complex songs (like bengalese finch) exhibit greater activity dependent genomic responses, larger nucleus volumes and higher cell counts compared to the species with simpler vocalizations like zebra finch. The nucleus volume comparisons show trends consistent with the earlier zebra finch studies. To investigate how species-specific acoustic structure influence’s premotor nucleus function, we performed bilateral HVC lesions in owl finches and compared pre and post lesion vocalizations. The primary deficit was temporal structure, the post-lesion songs showed markedly increased inter-syllable gaps, whereas mean syllable durations remained largely unchanged. This indicates that in owl finches, HVC plays a critical role in temporal sequencing but is less essential for maintaining the spectral structure characteristic of harmonic stacks. Together, these findings highlight both conserved and divergent roles HVC across Estrildid songbirds, revealing how neural circuits are adapted to species-specific vocal architectures and levels of song complexity.