14 DAY TRIAL // The researchers at Rutgers, The State University of New Jersey, have located the place in the brain where songbirds store the memories of their parents' songs. The discovery also has implications for humans, because humans and songbirds are among the few animals that learn to vocalize by imitating their caregivers.
Vicario, Phan and Pytte worked with zebra finches, tiny songbirds native to Australia and favored by researchers because they breed well in captivity. There are other animals that also learn vocalizations by imitating members of their species - whales, dolphins and parrots, for instance - but they take a long time to mature, are endangered or are too difficult to work with in laboratories.
Vicario, an associate professor of psychology, and Phan, a postdoctoral associate in psychology, study sensorimotor processes involved in the acquisition and production of learned behaviors. Pytte, a postdoctoral associate in the department of biology at Wesleyan University in Middletown, Conn., studies the neurobiology of song production. The team performed the experiments in Vicario's lab, where he raises zebra finches, Bengalese finches and canaries.
There are two types of bird songs. One that is done both by the mother and father is a call-song, providing information about food or predators. The other one- that is done exclusively by the father, is a courtship song designed for attracting the females. Young male zebra finches hear their father's song and imitate them. At first, the bird's efforts are clumsy - the songbird equivalent of a baby's first babbling syllables. But eventually, the young bird manages an almost complete copy of his parent's song including some improvised elements.
Birdsong scientists have discovered that a young bird will remember any adult's song heard during a key period of its infancy. The young bird can even remember and imitate songs from other species, provided they fall within a certain range. When offered a choice, however, between recorded songs from their own species and those of other species, the young birds pick their own species. "If the processes of learning in young birds and human babies have formal similarities, which it now seems they do, then studying the songbird brain can tell us how this imitation trick is actually performed by cells in the brain," Vicario says. "The bird's brain provides a laboratory for studying how memories that underlie vocal learning are stored in the brain and how the stored memories are used to guide the development of vocalization." The scientists report that songs are stored in a part of the brain involved in hearing. This suggests the auditory version of the caregiver's song is stored first, and that it may serve to guide the vocal learning process.
"There is independent evidence, notably from work done by Patricia Kuhl of the University of Washington in Seattle, that something similar may underlie the acquisition of human speech by infants and, thus, be part of the mechanism that allows kids to learn any human language if they start early enough," Vicario says. "These findings are exciting," Kuhl says of the research reported in the paper. "They provide neurobiological evidence that helps explain human infants' acquisition of speech."