Auditory-Vocal Mirror Neurons for Learned Vocal Communication

Imitation is an essential engine for propagating human culture, enabling people to transmit art, music, speech, and language from one generation to the next. The young child’s ability to vocally imitate the speech of parents and peers is arguably one of the most essential forms of learning for human societies, because it provides the foundation for spoken language (Locke, 1993). The sensorimotor interactions that underlie human speech learning and communication remain poorly understood. An emerging idea is that sensorimotor neurons selectively active during both the execution and observation of specific gestures (i.e., mirror neurons) could play an important role in the learning, perception, and production of speech and language (Iacoboni et al., 2005; Kohler et al., 2002; Rizzolatti, 2005; Rizzolatti & Arbib, 1999, 1998; Rizzolatti & Craighero, 2004). Explicitly testing this idea is impractical, and consequently whether mirror neurons are important to human speech and language remains a matter of substantial debate. In this context, an important goal is to develop a suitable animal model in which to search for auditory-vocal mirror neurons and explore how they function to enable learned vocal communication. Songbirds afford two great advantages in attaining this goal. First, they are one of the few nonhuman animals to communicate using learned vocalizations. Indeed, despite the fundamental importance of speech learning to human societies, and the widespread use of vocal communication by other animals, vocal learning in nonhuman species is quite rare. Importantly, studies in nonhuman primates have failed to uncover evidence of vocal learning. Oscine songbirds (order: Passeriformes) culturally transmit their courtship songs from one generation to the next, providing an experimentally tractable system in which to study mechanisms of vocal imitation and learned vocal communication (Doupe & Kuhl, 1999; Marler, 1970; Marler & Tamura, 1964). Moreover, both songbirds and humans learn to produce a complex and temporally precise sequence of vocal gestures using auditory signals originating from tonotopically organized hair cells of the inner ear. Therefore, even though Auditory-Vocal Mirror Neurons for Learned Vocal Communication