Singing activity‐driven Arc expression associated with vocal acoustic plasticity in juvenile songbird

Abstract

Learned vocalization, including birdsong and human speech, is acquired through self‐motivated vocal practice during the sensitive period of vocal learning. The zebra finch (Taeniopygia guttata) develops a song characterized by vocal variability and crystallizes a defined song pattern as adulthood. However, it remains unknown how vocal variability is regulated with diurnal singing during the sensorimotor learning period. Here, we investigated the expression of activity‐dependent neuroplasticity‐related gene Arc during the early plastic song phase to examine its potential association with vocal plasticity. We first confirmed that multiple acoustic features of syllables in the plastic song were dramatically and simultaneously modulated during the first 3 hr of singing in a day and the altered features were maintained until sleep. In a concurrent manner, Arc was intensely induced during morning singing and a subsequent attenuation during afternoon singing in the robust nucleus of the arcopallium (RA) and the interfacial nucleus of the nidopallium (NIf). The singing‐driven Arc expression was not altered by circadian rhythm, but rather reduced during the day as juveniles produced more songs. Song stabilization accelerated by testosterone administration in juveniles was accompanied with attenuation of Arc induction in RA and NIf. In contrast, although early‐deafened birds produced highly unstable song even at adulthood, singing‐driven Arc expression was not different between intact and early‐deafened adults. These results suggest a potential functional link between Arc expression in RA and NIf and vocal plasticity during the sensorimotor phase of song learning. Nonetheless, Arc expression did not reflect the quality of bird's own song or auditory feedback.

Inter‐ and intra‐specific differences in muscarinic acetylcholine receptor expression in the neural pathways for vocal learning in songbirds

“…We administrated T to juvenile zebra finches before the onset of first singing at 30 phd. We observed a decrease in acoustic variability across song bouts in T‐implanted juvenile zebra finches 2 weeks after of T‐implantation (Hayase & Wada, ). At this developmental time point (47.64 ± 2.9 phd), we compared their chrm2 expression level in HVC with that of age‐matched normal juveniles.…”

“…Exogenous testosterone (T) was implanted as described before (Hayase & Wada, ). Each bird was anesthetized by an intraperitoneal injection of pentobarbital (6.48 mg/ml; 60 μl/10 g body weight).…”

Vocal practice regulates singing activity–dependent genes underlying age-independent vocal learning in songbirds

“…Singing behavior generates robust neuronal activity in the song system, including RA and other song nuclei, throughout a bird’s life from juvenile to adult stages [ 31 , 48 , 59 – 61 ]. However, some immediate-early genes are more highly induced by singing in the song nuclei (e.g., egr1 [ zenk ] and Arc in RA and penk in HVC) in juvenile than adult stages, although the causal reason of the developmental different induction is not known [ 13 , 17 – 19 ]. In this study, we found that RA shows a reduction of singing activity–dependent gene induction during the accumulation of singing experience.…”

“…Developed slides were Nissl-stained with a cresyl violet acetate solution (Sigma) for the capture of high-resolution images. For quantification of mRNA signal, exposed X-ray films of brain images were digitally scanned under a microscope (Leica, Z16 APO) connected to a CCD camera (Leica, DFC490) with Application Suite V3 imaging software (Leica), as previously described [ 12 , 13 , 19 , 20 ]. To minimize handling bias for signal detection among experimental groups, we performed in situ hybridization using multiple brain sections at once for each probe and exposed S 35 -riboprobe hybridized brain sections on the same sheet of X-ray films.…”

“…The song nuclei are interconnected to form neural pathways for vocal learning and production [ 1 , 16 ]. Some of the singing activity–dependent genes are differentially regulated in the song nuclei between juvenile and adult stages [ 13 , 17 – 19 ]. However, a large variety of genes are developmentally regulated as age-related genes during the critical period of vocal learning in the song nuclei [ 20 – 22 ].…”