In a paper published today in the Proceedings of the National Academy of Sciences, David Vicario and Mimi Phan of Rutgers, and Carolyn Pytte of Wesleyan University, report that songbirds store the memory of caregivers' songs 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. The paper is titled "Early Auditory Experience Generates Long-Lasting Memories That May Subserve Vocal Learning in Songbirds."
"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."
Vicario, Phan and Pytte worked with zebra finches, tiny songbirds native to Australia and favored by researchers because they breed well in captivity and all year- round. 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 reported in the paper in Vicario's lab, where he raises zebra finches, Bengalese finches and canaries.
The father contributes equally to childcare in zebra finch families and does all the singing, Vicario says. "In everyday English, 'song' and 'call' mean the same thing, but in scientific language, they're different," Vicario says. "Calls communicate information about food and predators, and males and females both use them," he says. "A song is a vocal behavior used in male-male interactions and in courtship of females, and in most songbird species, only the male sings." A young zebra finch will hear his father's song, remember and imitate it. 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 that includes some improvised elements.
Birdsong scientists use the word "tutor" to describe the bird whose song the young bird copies and remembers because they've found that a young songbird will form a memory of any adult's song heard during a key period in infancy. In fact, the young bird will remember and imitate the songs of songbirds 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."