Analogies of human speech and bird song: From vocal learning behavior to its neural basis

Abstract

Vocal learning is a complex acquired social behavior that has been found only in very few animals. The process of animal vocal learning requires the participation of sensorimotor function. By accepting external auditory input and cooperating with repeated vocal imitation practice, a stable pattern of vocal information output is eventually formed. In parallel evolutionary branches, humans and songbirds share striking similarities in vocal learning behavior. For example, their vocal learning processes involve auditory feedback, complex syntactic structures, and sensitive periods. At the same time, they have evolved the hierarchical structure of special forebrain regions related to vocal motor control and vocal learning, which are organized and closely associated to the auditory cortex. By comparing the location, function, genome, and transcriptome of vocal learning-related brain regions, it was confirmed that songbird singing and human language-related neural control pathways have certain analogy. These common characteristics make songbirds an ideal animal model for studying the neural mechanisms of vocal learning behavior. The neural process of human language learning may be explained through similar neural mechanisms, and it can provide important insights for the treatment of language disorders.

Call combination production is linked to the social environment in Western Australian magpies ( Gymnorhina tibicen dorsalis )

“…[41][42][43]), but we still know very little about social influences on the ontogeny of non-song combinatoriality, including the potential factors driving its development [44]. Indeed, although open-ended learners continue to acquire and modify vocalizations throughout life [45], auditory-vocal learning is suggested to occur most rapidly during an early vocal development stage in humans and other open-ended vocal learners [46,47]. Thus, it seems prudent to (i) investigate the relationship between social complexity and call combination production and (ii) separately investigate how the social environment may influence call combination production in juveniles compared with adults.…”

Hemispheric dominance in HVC is experience-dependent in juvenile male zebra finches

“…Zebra finches learn their song in the same way that human children learn to speak, by listening to and imitating adults. For both species, exposure to adults early in development is critical for the emergence of species-specific vocalizations 21 – 24 . The zebra finch song system also shares anatomical similarities with the human language system, including premotor nuclei, a corticostriatal loop, and a specialized direct connection between the motor cortex and motor neurons of the vocal musculature 25 .…”

“…The LMAN performs an analogous function to Broca’s area in humans, while the RA performs a function similar to the laryngeal motor cortex (LMC). The HVC is functionally analogous to Broca’s area, as it receives auditory input and projects to the primary motor pathway and the anterior forebrain loop 24 . However, comparisons of gene expression profiles and cell-type markers indicate that the HVC may be anatomically homologous to the LMC 28 , 30 – 32 .…”