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Thursday, March 12, 2015

foundations of vocal learning

Mice don’t need the cortex to sing their songs

Laboratory mouse. Image: anyaivanova/Shutterstock
Laboratory mouse. Image: anyaivanova/Shutterstock
Mice lacking the cerebral cortex develop normal song. Image: Kurt Hammerschmidt
Mice lacking the cerebral cortex develop normal song. Image: Kurt Hammerschmidt

The human language is unique in that we can refer to objects, events and ideas. The combination of syllables and words enables humans to generate an infinite number of expressions. An important prerequisite for language is the ability to imitate sounds, i.e. to store acquired acoustic information and to use this for one's own vocal production. Cortical structures in the brain play a crucial role in this. While songbirds and certain marine mammals are capable of such vocal learning, there is very little evidence for vocal learning in terrestrial mammals - not even in our closest living relatives, the chimpanzees. Nonhuman primate vocal production is largely restricted to an innate repertoire of sounds. In order to explain the foundations of vocal learning, mice attracted increasing attention in recent years. They are more closely related to humans than birds or dolphins, vocalize frequently, and there are numerous so-called "mouse models", where certain genes can deliberately be manipulated. Besides, there was some evidence that to a certain extent mice could be capable of vocal learning. In their recently published study, Julia Fischer and Kurt Hammerschmidt of the German Primate Center (DPZ) in Goettingen together with colleagues from the Max Planck Institute for Biophysical Chemistry have shown that mice are less suited to study the foundations of vocal learning than previously assumed. Animals that do not have a cerebral cortex due to a genetic defect do not differ from healthy mice in their vocalization ("song"). Their vocalizations are thus controlled in evolutionarily older brain areas and are not dependent on cortical processing (Published in Scientific Reports). 

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