Biology subjects

dos Santos, E. B.

Publications and source records attributed to dos Santos, E. B..

3 recordsLinked to original sources

bioRxiv2023

Does the syrinx, a peripheral structure, constrain effects of sex steroids on behavioral sex reversal in adult canaries?

We previously confirmed that effects of testosterone (T) on singing activity and on the volume of brain song control nuclei are sexually differentiated in adult canaries: females are limited in their ability to respond to T as males do. Here we expand on these results by focusing on sex differences in the production and performance of trills, i.e., rapid repetitions of song elements. We analyzed more than 42,000 trills recorded over a period of 6 weeks from 3 groups of castrated males and 3 groups of photoregressed females that received Silastic implants filled with T, T plus estradiol or left empty as control. Effects of T on the number of trills, trill duration and percent of time spent trilling were all stronger in males than females. Irrespective of endocrine treatment, trill performance assessed by vocal deviations from the trill rate versus trill bandwidth trade-off was also higher in males than in females. Finally, inter-individual differences in syrinx mass were positively correlated with trill production in males but not in females. Given that T increases syrinx mass and syrinx fiber diameter in males but not in females, these data indicate that sex differences in trilling behavior are related to sex differences in syrinx mass and syrinx muscle fiber diameter that cannot be fully reversed by sex steroids in adulthood. Sexual differentiation of behavior thus reflects organization not only of the brain but also of peripheral structures.

animal behavior and cognition↗

bioRxiv2023

Auditory feedback-independent maintenance of song performance through daily singing in adult songbirds

Many songbirds learn to produce songs through vocal practice early in life and continue to sing numerous renditions of their learned songs daily throughout their lifetime. While it is well-known that adult songbirds sing as part of a mating ritual, the functions of singing behavior outside of reproductive contexts are not fully understood. Here, we demonstrate that adult singing outside of reproductive contexts serves to prevent passive changes in song performance. We suppressed the daily singing behavior of adult zebra finches produced in the solo context for two weeks using a reversible behavioral manipulation and examined the effect on song performance. Our results indicated that suppressing daily singing significantly decreased the pitch of song elements and both the amplitude and duration of song motifs. These findings suggest that adult song is not acoustically stable without singing, and that adult birds maintain their song performance by daily singing. Moreover, we found that the changes in song structure caused by singing suppression were substantially recovered within two weeks of free singing, even in deafened birds. Thus, the recovery of song performance does not necessarily require auditory feedback but is predominantly caused by singing behavior per se (i.e., the physical act of singing). Finally, unlike the auditory feedback-dependent song plasticity reported previously, the passive song changes caused by singing suppression were not significantly dependent on age. Taken together, our findings demonstrate that adult songbirds maintain song performance by preventing passive song changes through the physical act of daily singing throughout their life. Such daily singing likely functions as vocal training to maintain the neural and/or muscular system in optimal conditions for song performance in reproductive contexts, similar to how human singers and athletes practice daily to maintain their performance.

animal behavior and cognition↗

bioRxiv2021

Perineuronal nets in HVC and plasticity in male canary song

Songbirds learn their vocalizations during developmental sensitive periods of song memorization and sensorimotor learning. Some seasonal songbirds, called open-ended learners, recapitulate transitions from sensorimotor learning and song crystallization on a seasonal basis during adulthood. In adult male canaries, sensorimotor learning occurs each year in autumn and leads to modifications of the syllable repertoire during successive breeding seasons. We previously showed that perineuronal nets (PNN) expression in song control nuclei decreases during this sensorimotor learning period. Here we explored the causal link between PNN expression in adult canaries and song modification by enzymatically degrading PNN in HVC, a key song control system nucleus. Three independent experiments identified limited effects of the PNN degradation in HVC on the song structure of male canaries. They clearly establish that presence of PNN in HVC is not required to maintain general features of crystallized song. Some suggestion was collected that PNN are implicated in the stability of song repertoires but this evidence is too preliminary to draw firm conclusions and additional investigations should consider producing PNN degradations at specified time points of the seasonal cycle. It also remains possible that once song has been crystallized at the beginning of the first breeding season, PNN no longer play a key role in determining song structure which could be tested by treatments with ChABC at key step in ontogeny. It would in this context be important to develop multiple stereotaxic procedures allowing the simultaneous bilateral degradation of PNN in several song control nuclei for extended periods.

neuroscience↗