ROLE OF A TELENCEPHALIC NUCLEUS IN THE DELAYED SONG LEARNING OF SOCIALLY ISOLATED ZEBRA FINCHES

Male zebra finches normally learn their song from adult models during a restricted period of juvenile development. If song models are not av ailable then, juveniles develop an isolate song which can be modified in adulthood. In this report we investigate the features of juvenile e xperience that underly the timing of song learning. Juvenile males rai sed in soundproof chambers or in visual isolation from conspecifics de veloped stable isolate song. However, whereas visual isolate song note s were similar to those of colony-reared males, soundproof chamber iso lates included many phonologically abnormal notes in their songs. Desp ite having stable isolate songs, both groups copied new notes from tut ors presented to them in adulthood (2.7 notes per bird for soundproof chamber isolates, 4.4 notes per bird for visual isolates). Old notes w ere often modified or eliminated. We infer that social interactions wi th live tutors are normally important for closing the sensitive period for song learning. Lesions of a forebrain nucleus (IMAN) had previous ly been shown to disrupt juvenile song learning, but not maintenance o f adult song for up to 5 weeks after surgery. In this study, colony-re ared adult males given bilateral lesions of IMAN retained all their so ng notes for up to 4-7.5 months after lesioning. However, similar lesi ons blocked all song note acquisition in adulthood by both visual and soundproof chamber isolates. Other work has shown that intact hearing is necessary for the maintenance of adult zebra finch song. We infer t hat auditory pathways used for song maintenance and acquisition differ : IMAN is necessary for auditorily guided song acquisition whether by juveniles or adults-but not for adult auditorily guided song maintenan ce. (C) 1993 John Wiley & Sons, Inc.