Coordinated Control of Respiratory Pattern During Locomotion in Birds

SYNOPSIS. Cineradiographic studies of magpies and pigeons inflight, coupled with measurements of air sac pressures and tracnealairflows, indicate a significant compressive effect of downstrokeand expansive effect of upstroke. These mechanical impacts ofthe wingbeat cycle upon the respiratory system likely contributeto a phasic coordination of the two cycles that, in these species,ensures that upstroke corresponds to the transition into inspirationand downstroke corresponds to the transition into expiration,regardless of the ratio of wingbeats to breaths. Similar phasicpatterns have been reported for other birds. Respiratory muscleactivity patterns indicate that the upstroke may indeed assistinspiratory airflow and that the downstroke may assist expiratoryairflow. Stimulation of ventilation with 5% CO₂ during flightdid not alter the phasic coordination patterns between respiratoryand wingbeat cycles in either pigeons or magpies. These data support the concepts that 1) interactions of locomotorand respiratory central controllers likely play an importantrole in regulating respiratory pattern during locomotion inbirds and 2) peripheral neural feedback of information aboutthe mechanical impact of the wingbeat cycle upon the functioningof the respiratory pump is likely to make a strong contributionto a respiratory pattern that is coordinated with the locomotorpattern in an energetically appropriate phasic relationship.The failure to alter that pattern with chemical stimulationof breathing suggests that the neural interaction between locomotorand respiratory networks is quite robust