COORDINATED CONTROL OF RESPIRATORY PATTERN DURING LOCOMOTION IN BIRDS

Cineradiographic studies of magpies and pigeons in flight, coupled wit h measurements of air sac pressures and tracheal airflows, indicate a significant compressive effect of downstroke and expansive effect of u pstroke, These mechanical impacts of the wingbeat cycle upon the respi ratory system likely contribute to a phasic coordination of the two cy cles that, in these species, ensures that upstroke corresponds to the transition into inspiration and downstroke corresponds to the transiti on into expiration, regardless of the ratio of wingbeats to breaths, S imilar phasic patterns have been reported for other birds, Respiratory muscle activity patterns indicate that the upstroke may indeed assist inspiratory airflow and that the downstroke may assist expiratory air flow Stimulation of ventilation with 5% CO2 during flight did not alte r the phasic coordination patterns between respiratory and wingbeat cy cles in either pigeons or magpies. These data support the concepts tha t 1) interactions of locomotor and respiratory central controllers lik ely play an important role in regulating respiratory pattern during lo comotion in birds and 2) peripheral neural feedback of information abo ut the mechanical impact of the wingbeat cycle upon the functioning of the respiratory pump is likely to make a strong contribution to a res piratory pattern that is coordinated with the locomotor pattern in an energetically appropriate phasic relationship. The failure to alter th at pattern with chemical stimulation of breathing suggests that the ne ural interaction between locomotor and respiratory networks is quite r obust.