Animal models, songbirds particularly, are increasingly used to study the human capacity for speech and language. In the light of understanding both language evolution and individual language... Show moreAnimal models, songbirds particularly, are increasingly used to study the human capacity for speech and language. In the light of understanding both language evolution and individual language acquisition these models are highly valuable, provided that they are studied within a valid comparative framework. In the past few decades, non-invasive methods such as functional Magnetic Resonance Imaging (fMRI) and Near-InfraRed Spectroscopy (NIRS) have become available for human as well as animal brain research. In the studies discussed in this thesis, fMRI is employed to unravel the neural correlates of vocal learning in the human and songbird brain. Specifically, fMRI in both songbirds and humans is used to study the neural mechanisms underlying birdsong learning and human artificial grammar learning. In a series of fMRI studies investigating these neural mechanisms in adult and juvenile zebra finches and human adults, this thesis compares the neural substrates of song learning in birds with those of language learning in humans. Studies in both species show correlations between behavioral learning of song or speech and neural activity. These results contribute to the songbird model for human vocal learning. Show less
Birdsong and human speech are both complex behaviours which show striking similarities mainly thought to be present in the area of development and learning. The most important parameters in human... Show moreBirdsong and human speech are both complex behaviours which show striking similarities mainly thought to be present in the area of development and learning. The most important parameters in human speech are vocal tract resonances, called formants. Different formant patterns characterize different vowels and are produced by moving articulators such as tongue and lips. However, not much is known about the production and perception of vocal tract resonances by birds. In this thesis I show that both songbirds and parrots use different articulators, comparable to humans, to modify the sound produced. While in songbirds beak gape and the expansion of the oropharyngeal-esophageal cavity are the most important articulators, parrots exhibit prominent tongue movements which also might explain their sophisticated ability to mimic human speech. Regarding formant perception I show that zebra finches can discriminate human words differing only in their vowels and categorize these words independent of speaker identity. To do so the birds employ, just like humans, a combination of intrinsic and extrinsic speaker normalization. Furthermore, when tested for a cue weighting bias both zebra finches and Dutch adults weight higher frequencies stronger. These results indicate that the mechanisms underlying vocal production and perception in birds and humans exhibit more similarities than realized before and studying birdsong will increase our knowledge about the emergence of these mechanisms and might even shed light on the evolution of human speech. Show less
