Neurobiology of song learning

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Birdsong is a culturally transmitted behavior that depends on a juvenile songbird's ability to imitate the song of an adult tutor. Neurobiological studies of birdsong can reveal how a complex form of imitative learning, which bears strong parallels to human speech learning, can be understood at the level of underlying circuit, cellular, and synaptic mechanisms. This review focuses on recent studies that illuminate the neurobiological mechanisms for singing and song learning.

Section snippets

Introduction to song learning

Juvenile songbirds learn to sing during a sensitive period comprising two sequential phases  sensory and sensorimotor learning  both dependent on auditory experience [1, 2]. During sensory learning, the juvenile listens to and memorizes one or more tutor songs. In the ensuing phase of sensorimotor learning, which may involve tens or even hundreds of thousands of song repetitions over many weeks, the juvenile uses auditory feedback to match its song to the memorized model. Two hallmarks of

Introduction to neural circuits for song

The songbird's brain contains a system of interconnected brain nuclei specialized for singing and song learning (i.e. the song system; Figure 1) [13, 14]. The song system comprises two major parts, a song motor pathway (SMP), which spans from the telencephalon to the brainstem vocal-respiratory network, and an anterior forebrain pathway (AFP) that traverses the telencephalon, striatum, and thalamus, and which resembles mammalian cortical–basal ganglia pathways [15]. Chronic recordings in

Song motor codes and central mechanisms for generating song variability

Current evidence places HVC at the apex of a song motor patterning network. Even though HVC receives input from several other song nuclei, HVC is the song nucleus most removed from the vocal periphery where neurons display time-locked singing-related activity and where lesions permanently disrupt song. What is the nature of the song motor code transmitted by HVC? A landmark study in singing zebra finches showed that individual HVCRA neurons fire only once per entire motif (a polysyllabic phrase

The search for central representations of auditory feedback

Instructive signals for sensorimotor learning must ultimately arise from feedback-dependent performance evaluation. A parsimonious idea is that singing-related auditory feedback is processed by the AFP, enabling this pathway to evaluate performance and instructively modify song motor commands. In fact, recordings made in the AFP of anesthetized birds detect neurons that respond selectively to playback of the bird's own song, fueling speculation that the AFP receives feedback-related information

The search for central representations of tutor song memories

How and where tutor song memories might be encoded in the juvenile's brain remains a matter of debate. Two lines of evidence have implicated the AFP: first, when NMDA receptors in LMAN of juvenile zebra finches are transiently blocked during tutoring, copying is subsequently impaired [54]; second, recordings in anesthetized zebra finches during sensorimotor learning detect some LMAN neurons that are selective for the tutor's song [55]. Intriguingly, some tutor-selective cells could be detected

References and recommended reading

Papers of particular interest, published within the period of review, have been highlighted as:

  • • of special interest

  • •• of outstanding interest

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