Translating birdsong: songbirds as a model for basic and applied medical research

Development of neural responsivity to vocal sounds in higher level auditory cortex of songbirds

Like humans, songbirds learn vocal sounds from "tutors" during a sensitive period of development. Vocal learning in songbirds therefore provides a powerful model system for investigating neural mechanisms by which memories of learned vocal sounds are stored. This study examined whether NCM (caudo-medial nidopallium), a region of higher level auditory cortex in songbirds, serves as a locus where a neural memory of tutor sounds is acquired during early stages of vocal learning. NCM neurons respond well to complex auditory stimuli, and evoked activity in many NCM neurons habituates such that the response to a stimulus that is heard repeatedly decreases to approximately one-half its original level (stimulus-specific adaptation). The rate of neural habituation serves as an index of familiarity, being low for familiar sounds, but high for novel sounds. We found that response strength across different song stimuli was higher in NCM neurons of adult zebra finches than in juveniles, and that only adult NCM responded selectively to tutor song. The rate of habituation across both tutor song and novel conspecific songs was lower in adult than in juvenile NCM, indicating higher familiarity and a more persistent response to song stimuli in adults. In juvenile birds that have memorized tutor vocal sounds, neural habituation was higher for tutor song than for a familiar conspecific song. This unexpected result suggests that the response to tutor song in NCM at this age may be subject to top-down influences that maintain the tutor song as a salient stimulus, despite its high level of familiarity.

Arguing about innateness

This paper lays out the components of a language acquisition model, the interconnections among the components, and the differing stances of nativism and empiricism about syntax. After demonstrating that parsimony cannot decide between the two stances, the paper analyzes nine examples of evidence that have been used to argue for or against nativism, concluding that most pieces of evidence are either irrelevant or suggest that language is special but need not invoke innate ideas. Two pieces of evidence - the development of home sign languages and the acquisition of Determiners - do show not just that language is special but that the child has innate syntactic content. The existential claim that nativism makes - there is at least one innate syntactic idea - is an easier claim to verify than the universal claim that empiricism makes - there are no innate syntactic ideas.

Cadherins: potential regulators in the faculty of language

The cadherin superfamily is a large (now more than 100 proteins) protein family originally identified as cell adhesion molecules. Each cadherin shows distinct expression patterns in the nervous system, and their expressions are both spatially and temporally regulated and diverse among different species. Mounting evidence has suggested that cadherins play multiple roles in neural development and functions. Recently, using songbirds and mice, the potential role of cadherins in vocal behavior has been demonstrated. Here, we will briefly introduce general function of cadherins, and analyze the potential involvement of cadherins in vocal behaviors and their evolution.

Dissection and downstream analysis of zebra finch embryos at early stages of development

The zebra finch (Taeniopygiaguttata) has become an increasingly important model organism in many areas of research including toxicology, behavior, and memory and learning. As the only songbird with a sequenced genome, the zebra finch has great potential for use in developmental studies; however, the early stages of zebra finch development have not been well studied. Lack of research in zebra finch development can be attributed to the difficulty of dissecting the small egg and embryo. The following dissection method minimizes embryonic tissue damage, which allows for investigation of morphology and gene expression at all stages of embryonic development. This permits both bright field and fluorescence quality imaging of embryos, use in molecular procedures such as in situ hybridization (ISH), cell proliferation assays, and RNA extraction for quantitative assays such as quantitative real-time PCR (qtRT-PCR). This technique allows investigators to study early stages of development that were previously difficult to access.

A variability-generating circuit goes awry in a songbird model of the FOXP2 speech disorder

FOXP2 mutations cause a monogenic speech disorder in humans. In this issue of Neuron, Murugan et al. (2013) show that knockdown of FoxP2 in the songbird basal ganglia causes abnormal vocal variability and excess bursting in a frontal cortical nucleus.

Mouse models of neurodevelopmental disease of the basal ganglia and associated circuits

This chapter focuses on neurodevelopmental diseases that are tightly linked to abnormal function of the striatum and connected structures. We begin with an overview of three representative diseases in which striatal dysfunction plays a key role--Tourette syndrome and obsessive-compulsive disorder, Rett's syndrome, and primary dystonia. These diseases highlight distinct etiologies that disrupt striatal integrity and function during development, and showcase the varied clinical manifestations of striatal dysfunction. We then review striatal organization and function, including evidence for striatal roles in online motor control/action selection, reinforcement learning, habit formation, and action sequencing. A key barrier to progress has been the relative lack of animal models of these diseases, though recently there has been considerable progress. We review these efforts, including their relative merits providing insight into disease pathogenesis, disease symptomatology, and basal ganglia function.

The architecture of speech production and the role of the phoneme in speech processing

Speech production has been studied within a number of traditions including linguistics, psycholinguistics, motor control, neuropsychology, and neuroscience. These traditions have had limited interaction, ostensibly because they target different levels of speech production or different dimensions such as representation, processing, or implementation. However, closer examination of reveals a substantial convergence of ideas across the traditions and recent proposals have suggested that an integrated approach may help move the field forward. The present article reviews one such attempt at integration, the state feedback control model and its descendent, the hierarchical state feedback control model. Also considered is how phoneme-level representations might fit in the context of the model.