Midbrain control of vocalizations in redwinged blackbirds (Agelaius phoeniceus)

Chronically indwelling electrodes were used to stimulate the midbrain of unrestrained male redwinged blackbirds. Vocalizations were elicited only by stimulating non-auditory regions of the torus semicircularis. Many of the vocalizations given by this species in its natural habitat were elicited by stimulating the torus. Some evoked calls had structures intermediate between different call types. Sounds not found in the natural repertoire were also evoked. The structure and temporal patterning of vocalizations evoked by torus stimulation could be altered by manipulating stimulation parameters. Furthermore, dramatic changes in evoked vocal patterns occurred with only minor parameted changes. However, the vocal patterns produced by such manipulations varied for different individuals. These observations suggest that non-auditory regions of the torus semicircularis exert a profound coordinating influence upon the respiratory and syringo-tracheal components of the avian vocal apparatus.