Neural systems for vocal learning in birds and humans: a synopsis.

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2007-12-01

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Abstract

I present here a synopsis on a hypothesis that I derived on the similarities and differences of vocal learning systems in vocal learning birds for learned song and in humans for spoken language. This hypothesis states that vocal learning birds-songbirds, parrots, and hummingbirds-and humans have comparable specialized forebrain regions that are not found in their close vocal non-learning relatives. In vocal learning birds, these forebrain regions appear to be divided into two sub-pathways, a vocal motor pathway mainly used to produce learned vocalizations and a pallial-basal-ganglia-thalamic loop mainly used to learn and modify the vocalizations. I propose that humans have analogous forebrain pathways within and adjacent to the motor and pre-motor cortices, respectively, used to produce and learn speech. Recent advances have supported the existence of the seven cerebral vocal nuclei in the vocal learning birds and the proposed brain regions in humans. The results in birds suggest that the reason why the forebrain regions are similar across distantly related vocal learners is that the vocal pathways may have evolved out of a pre-existing motor pathway that predates the ancient split from the common ancestor of birds and mammals. Although this hypothesis will require the development of novel technologies to be fully tested, the existing evidence suggest that there are strong genetic constraints on how vocal learning neural systems can evolve.

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10.1007/s10336-007-0243-0

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Jarvis, Erich D (2007). Neural systems for vocal learning in birds and humans: a synopsis. J Ornithol, 148(1). pp. 35–44. 10.1007/s10336-007-0243-0 Retrieved from https://hdl.handle.net/10161/11235.

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Jarvis

Erich David Jarvis

Adjunct Professor in the Deptartment of Neurobiology

Dr. Jarvis' laboratory studies the neurobiology of vocal communication. Emphasis is placed on the molecular pathways involved in the perception and production of learned vocalizations. They use an integrative approach that combines behavioral, anatomical, electrophysiological and molecular biological techniques. The main animal model used is songbirds, one of the few vertebrate groups that evolved the ability to learn vocalizations. The generality of the discoveries is tested in other vocal learning orders, such as parrots and hummingbirds, as well as non-vocal learners, such as pigeons and non-human primates. Some of the questions require performing behavior/molecular biology experiments in freely ranging animals, such as hummingbirds in tropical forest of Brazil. Recent results show that in songbirds, parrots and hummingbirds, perception and production of song are accompanied by anatomically distinct patterns of gene expression. All three groups were found to exhibit vocally-activated gene expression in exactly 7 forebrain nuclei that are very similar to each other. These structures for vocal learning and production are thought to have evolved independently within the past 70 million years, since they are absent from interrelated non-vocal learning orders. One structure, Area X of the basal ganglia's striatum in songbirds, shows large differential gene activation depending on the social context in which the bird sings. These differences may reflect a semantic content of song, perhaps similar to human language.

The overall goal of the research is to advance knowledge of the neural mechanisms for vocal learning and basic mechanisms of brain function. These goals are further achieved by combined collaborative efforts with the laboratories of Drs. Mooney and Nowicki at Duke University, who study respectively behavior and electrophysiological aspects of songbird vocal communication.


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