| 研究実績の概要 |
Vocal learning is the key behavioral basis for the acquisition of spoken human language. However, few animal groups, and none of humans’ close relatives, are vocal learners. Therefore, without sufficient scientific examination, it is a commonly held belief that “age (intrinsic maturation)” is one of the crucial factors for the closure of the critical/sensitive period of vocal learning. Against this, our study using songbirds provides a new insight that self-motivated vocal practice acts as a non-genetic factor to regulate vocal learning plasticity during the critical period. We prevented zebra finches, a closed-ended learning species, from singing during the critical period of song learning by postural manipulation, which enabled to separate life-long vocal experience from the effects of age. The singing-prevented birds retained a juvenile-like ability to acquire a tutored song even at adulthood after being released to freely sing. Genome-wide gene expression network analysis revealed that vocal plasticity is tightly linked to the expression dynamics of singing activity-dependent genes, but not of age-dependent genes. The significant transcriptional changes of activity-dependent genes occurred in the vocal motor nucleus RA projection neurons, which play a role in regulation of song phonology.
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