THE ROLE OF NONLINEAR DYNAMICS OF THE SYRINX IN THE VOCALIZATIONS OF A SONGBIRD

Birdsong is characterized by the modulation of sound properties over a wide range of timescales'. Understanding the mechanisms by which the brain organizes this complex temporal behaviour is a central motivatio n in the study of the song control and learning system(2-8). Here we p resent evidence that, in addition to central neural control, a further level of temporal organization is provided by nonlinear oscillatory d ynamics that are intrinsic to the avian vocal organ. A detailed tempor al and spectral examination of song of the zebra finch (Taeniopygia gu ttata) reveals a class of rapid song modulations that are consistent w ith transitions in the dynamical state of the syrinx. Furthermore, in vitro experiments show that the syrinx can produce a sequence of oscil latory states that are both spectrally and temporally complex in respo nse to the slow variation of respiratory or syringeal parameters. As a consequence, simple variations in a small number of neural signals ca n result in a complex acoustic sequence.