56-12 Sat Jan 2 Evidence for a proximal-distal gradient in muscle responses to a wind gust perturbation in the Egyptian fruit bat Rowley, KM*; Morris, A; Bortoni, A; Young, I; Boerma, D; Breuer, K; Swartz, SM; Brown University; Brown University; Brown University; Brown University; American Museum of Natural History; Brown University; Brown University kevin_rowley@brown.edu http://vivo.brown.edu/display/krowley
Bats fly with remarkable maneuverability as they navigate dense colonies and turbulent air. When subjected to unilateral gust perturbations in the lab, bats recovered typical flight kinematics within one wingbeat. We investigated motor control strategies enabling rapid recovery by assessing left-right symmetry in the activation of a proximal vs. a distal wing muscle. Previous studies of recovery in terrestrial vertebrates showed recovery responses involved load-insensitive recruitment of proximal muscles and load-sensitive recruitment of distal muscles. We hypothesized this proximal-distal control gradient is conserved in bats, and we would observe symmetric activation of the pectoralis major, the primary flight motor and a proximal muscle, and asymmetric activation of the extensor carpi radialis longus (ECRL) muscle, a distal digit extensor in the forearm. We trained five Rousettus aegyptiacus to fly through a corridor, collecting bilateral intramuscular electromyography (EMG) using a wireless data logger. During some trials, subjects experienced an air jet (2.5x body weight) to one wing. The timing, amplitude, and between-side correlation of the EMG signal showed pectoralis recruitment was symmetrical in all trials. ECRL activation differed in amplitude between left and right wings during the perturbed but not control trials, demonstrating asymmetric, perturbation-dependent recruitment in this distal muscle. We conclude that proximal muscle recruitment in our model bat species is not altered by a significant perturbation to flight, while distal muscles are recruited in a manner dependent on external forces.