SVR Murthy
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Reviews research on parallels between the acquisition of song in birds and learning of speech in humans. Both humans and songbirds learn complex vocalizations early, with a strong dependence on hearing adults they will imitate, and themselves as they practice, and a waning of this dependence as they mature. Innate predispositions for perceiving and learning correct sounds exist in both groups, although more evidence of innate descriptions of species-specific signals exists in songbirds. Humans also share with songbirds a primarily perceptual early phase of learning. Both have evolved a complex hierarchy of specialized forebrain areas in which motor and auditory centers interact closely, and which control lower vocal motor areas. In both groups, how auditory self-feedback is processed in these brain areas is unclear. Humans and songbirds have similar critical periods for vocal learning, with a greater ability to learn early in life. Although some features are not analogous, such as the capacity of language for meaning, abstraction, and flexible associations, similarities in how sensory experience is internalized and used to shape vocal outputs suggests similar neural mechanisms may be involved.


1) Birdsong offers an opportunity to study the neuronal circuits involved in a complex yet stereotyped behavior. Song is sometimes seen as a model for human speech.

2) Song has both an innate structure, and an essential learned component. Song learning takes place during an early critical period.

3) Song also requires practice and refinement during which hearing is essential. Studies of song are a premiere example of sensory motor integration.

4) The neural pathways for song are divided into two parts: a posterior pathway from forebrain to brainstem to syrinx involved in motor coordination and rhythm generation, and an anterior pathway involved in learning.

5) Our understanding of the function and mechanisms of vocal learning is incomplete. Lesion studies are still informative of the complex mechanisms involved in vocal learning.

References:

Andalman, A. S., Foerster, J. N. and Fee, M. S. Control of vocal and respiratory patterns in birdsong: dissection of forebrain and brainstem mechanisms using temperature. PLoS One 6, e25461.

Brenowitz, E. A., Margoliash, D. and Nordeen, K. W. (1997). An introduction to birdsong and the avian song system. J Neurobiol 33, 495-500.

Doupe, A. J. and Konishi, M. (1991). Song-selective auditory circuits in the vocal control system of the zebra finch. Proc Natl Acad Sci U S A 88, 11339-43. Doupe, A. J. and Kuhl, P. K. (1999).