Bilaterally symmetrical respiratory activity during lateralized birdsong

We investigated whether activity of expiratory muscles reflects lateralized activity of the vocal organ during production of birdsong, Respiration and syringeal motor activity were assessed in brown thrashers by monitoring bi lateral airflow and subsyringeal air sac pressure, together with the electr omyographic activity of expiratory abdominal muscles and vocal output. Acti vity of expiratory muscles was always present on both sides, regardless of whether song was produced bilaterally or on only one side of the syrinx. Th e average amplitude of expiratory EMG of one side does not change significa ntly, even if that side is silent during phonation. The temporal pattern of the electro myogram (EMG) was similar on both sides. Bilateral bursts of E MG activity on both sides accompanied changes in the rate of syringeal airf low, even when these flow fluctuations were generated only by one side of t he syrinx,during phonation. The temporal pattern of the electro myogram (EM G) was similar on both sides. Bilateral bursts of EMG activity on both side s accompanied changes in the rate of syringeal airflow, even when these flo w fluctuations were generated only by one side of the syrinx. Motor command s to the respiratory muscles therefore appear to be bilaterally distributed , in contrast to the lateralized motor control of the syrinx. (C) 1999 John Wiley & Sons, Inc.