Okanoya K, Yamaguchi A
Applied Ornithology Laboratory, National Agriculture Research Center, Ibaraki, Japan.
J Neurobiol. 1997 Oct;33(4):343-56.
Songbirds develop their songs by imitating songs of adults. For song learning to proceed normally, the bird's hearing must remain intact throughout the song development process. In many species, song learning takes place during one period early in life, and no more new song elements are learned thereafter. In these so-called close-ended learners, it has long been assumed that once song development is complete, audition is no longer necessary to maintain the motor patterns of full song. However, many of these close-ended learners maintain plasticity in overall song organization; the number and the sequence of song elements included in a song of an individual vary from one utterance to another, although no new song elements are added or lost in adulthood. It is conceivable that these species rely on continued auditory feedback to produce normal song syntax. The Bengalese finch is a close-ended learner that produces considerably variable songs as an adult. In the present study, we found that Bengalese finches require real-time auditory feedback for motor control even after song learning is complete; deafening adult finches resulted in development of abnormal song syntax in as little as 5 days. We also found that there was considerable individual variation in the degree of song deterioration after deafening. The neural mechanisms underlying adult song production in different species of songbirds may be more diverse than has been traditionally considered.
鸣禽通过模仿成年鸟的歌声来发展自己的歌声。为了使歌声学习正常进行，鸟类的听力在整个歌声发展过程中必须保持完好。在许多物种中，歌声学习发生在生命早期的一个阶段，此后不再学习新的歌声元素。在这些所谓的封闭式学习者中，长期以来人们一直认为，一旦歌声发展完成，听觉对于维持完整歌声的运动模式就不再必要。然而，许多这些封闭式学习者在整体歌声组织方面保持着可塑性；尽管成年后没有增加或丢失新的歌声元素，但个体歌声中包含的歌声元素的数量和顺序在每次发声时都有所不同。可以想象，这些物种依靠持续的听觉反馈来产生正常的歌声句法。 Bengalese雀是一种封闭式学习者，成年后会发出相当多变的歌声。在本研究中，我们发现Bengalese雀即使在歌声学习完成后，也需要实时听觉反馈来进行运动控制；使成年雀失聪会在短短5天内导致异常歌声句法的发展。我们还发现，失聪后歌声退化的程度存在相当大的个体差异。不同种类鸣禽成年后歌声产生的神经机制可能比传统认为的更加多样。
