Predicting plasticity: acute context-dependent changes to vocal performance predict long-term age-dependent changes

Abstract

Understanding the factors that predict and guide variation in behavioral change can lend insight into mechanisms of motor plasticity and individual differences in behavior. The performance of adult birdsong changes with age in a manner that is similar to rapid context-dependent changes to song. To reveal mechanisms of vocal plasticity, we analyzed the degree to which variation in the direction and magnitude of age-dependent changes to Bengalese finch song could be predicted by variation in context-dependent changes. Using a repeated-measures design, we found that variation in age-dependent changes to the timing, sequencing, and structure of vocal elements ("syllables") was significantly predicted by variation in context-dependent changes. In particular, the degree to which the duration of intersyllable gaps, syllable sequencing at branch points, and fundamental frequency of syllables within spontaneous [undirected (UD)] songs changed over time was correlated with the degree to which these features changed from UD song to female-directed (FD) song in young-adult finches (FDyoung). As such, the structure of some temporal features of UD songs converged over time onto the structure of FDyoung songs. This convergence suggested that the FDyoung song could serve as a stable target for vocal motor plasticity. Consequently, we analyzed the stability of FD song and found that the temporal structure of FD song changed significantly over time in a manner similar to UD song. Because FD song is considered a state of heightened performance, these data suggest that age-dependent changes could reflect practice-related improvements in vocal motor performance.

Behavioural responses to video and live presentations of females reveal a dissociation between performance and motivational aspects of birdsong

“…To analyse variation in song tempo between VD and LD song, we calculated the duration of the first motif of each song bout and analysed experimental variation in first motif durations using the same four-way factorial model as above (only first three bouts). Only the first motif in each bout was analysed for this comparison because motif durations change as bout length increases (e.g., Chi and Margoliash, 2001; Glaze and Troyer, 2006; James and Sakata, 2014; James and Sakata, 2015) and because bout lengths differed between VD and LD song (Figure 3; Table S2). There was no significant effect of any factor, including Condition, on song tempo (Figure 4C).…”

“…In cases where few UD songs were produced between female presentations, UD songs produced in the 30 minutes before and after the testing period were used for analysis (16.2 ± 2.9 UD song bouts per male)(e.g. James and Sakata, 2015; Sakata et al, 2008; Toccalino et al, 2016).…”

“…Introductory notes were quantified by starting with the note immediately preceding the first syllable of the bout and counting backwards until we reached ≥1 second of silence. Motif duration was defined as the duration from the onset of the first syllable of the motif to the onset to the last syllable of the motif and was used as the metric for song tempo (e.g., James and Sakata, 2015; Kao and Brainard, 2006; Sakata et al, 2008). We restricted the analysis of song tempo to the first motif of the bout, because motif durations have been found to change across the song bout and because bout durations differ between live and video presentations (see Results; Chi and Margoliash, 2001; Cooper and Goller, 2006; Glaze and Troyer, 2006).…”

Statistical learning for vocal sequence acquisition in a songbird

“…It is worth noting here that tutors and pupils were different ages when their songs were recorded and analyzed. This is potentially important because syllable sequencing changes over time in adult Bengalese finches 38,39 . For example, sequence variability at branch points decreases over time, due, in part, to a reduction in the number of branch point transitions.…”

“…The songs of individual Bengalese finches consist of a discrete, learned repertoire of syllables that are arranged both in highly stereotyped sequences ("motifs" or "chunks") and in sequences that vary from rendition to rendition ("branch points"; Fig. 1) 26,[33][34][35][36][37][38][39][40] . Previous studies have provided some insight into vocal sequence learning in Bengalese finches by comparing songs between tutors and pupils 41-43 ; for example, Yamashita et al (2008) analyzed the distribution of three-syllable sequences across two points in an individual's song development and found that the distribution approached that of his tutor's over time.…”