Biomechanics and bird brains

Just as human babies must learn how to talk, young songbirds have to learn to sing. By listening to other birds, each bird gradually develops its own voice—an individualized version of its species’ song. But despite that behavioral complexity, the physical mechanism of birdsong may actually be very simple. Gabriel Mindlin and colleagues, of the University of Buenos Aires, have found that they can realistically reproduce the songs of several species by using a dynamical systems model with just two time-dependent parameters: the pressure in the bird’s air sac and the tension of the tissue folds that vibrate to produce sound. Now, in collaboration with neuroscientist Daniel Margoliash of the University of Chicago, they’ve put their model to the ultimate test: What do the birds think? Margoliash and colleagues had previously found that when a bird listens to a recording of its own song, neurons in a certain “premotor” part of the brain fire in the same patterns as they did when the bird sang the song. When presented with a reproduction of the song from Mindlin and company’s model, the neurons duplicated about 58% of the original firing pattern. (They didn’t respond at all to a song of a different bird of the same species.) Furthermore, the neuron bursts coincided with discontinuities and local maxima in the model’s pressure and tension—time points whose significance was not always obvious from the song itself. (A. Amador et al., Nature 495, 59, 2013 .)—Johanna Miller