Song modulation and auditory feedback under different behavioral contexts in adult male Bengalese finches.

Birdsongs are classified into two types based on behavioral context: undirected song (US) and directed song (DS). Comparisons of US and DS following manipulations of auditory feedback have provided insights into the mechanisms underlying adult song plasticity and maintenance. When deafened as adults, the US of the Bengalese finch changes more rapidly than that of other species (e.g., zebra finch and budgerigar). However, it remains unclear whether the DS of Bengalese finches undergoes similarly rapid degradation. In this study, we deprived adult male Bengalese finches of auditory input and conducted long-term comparisons of US and DS following deafening. We examined the ratios of the number of higher syllables to that of low syllables (H/L) to characterize both US and DS at each time point before and after deafening. After deafening, the decrease in H/L emerged significantly faster and greater in US than in DS. The syllable sequence stereotypy score was lower in US than in DS at 7-14 days after deafening. These findings demonstrate that in adult Bengalese finches, auditory deprivation induces greater alteration more rapidly in US than in DS. We discuss the possibility that differences between US and DS arise from distinct neural activity patterns in the anterior forebrain pathway, which is involved in song learning and modification.