Meeting Abstract

P2.198  Thursday, Jan. 5  Neuromechanical Feedback during Dynamic Recovery after a Lateral Perturbation in Rapid Running Cockroaches MONGEAU, J.-M.; ALEXANDER, T.*; FULL, R.J.; Univ. of California, Berkeley; Morgan State Univ.; Univ. of California, Berkeley

When running animals are perturbed, recovery depends on the interplay between mechanical and neural feedback. Low-dimensional dynamic models complemented by kinematic and electromyographic (EMG) experiments of running cockroaches have demonstrated that mechanical self-stabilization can be sufficient to recover from perturbations. While mechanical feedback alone may be sufficient to maintain stability following small perturbations, measurements of instantaneous leg kinematic phase and frequency suggest that neural feedback is required when animals are pushed outside their passive stability basin. To study the interplay of neural and mechanical feedback during dynamic recovery, we perturbed rapid running cockroaches Blaberus discoidalis with a lateral impulse of a magnitude nearly twice the running speed (0.67 ± 0.03 m s-1). We hypothesized that the early phase of recovery would be dominated by mechanical feedback followed by neural feedback. To identify the presence of neural feedback, we analyzed the EMG patterns of putative control muscles in the hind leg (178,179). Animals ran at an average, preferred escape speed of 36.2 ± 7.0 cm s-1 while experiencing peak lateral impulses of 1.35 ± 0.15Gs on a moving cart. We observed evidence of neural feedback in EMG signals during the second post-perturbation stride (~100 ms after perturbation). Frequency of post-perturbation signals after 2 strides decreased relative to pre-perturbation recordings (median period increase = 4.9 ms; P = 0.001). Post-perturbation changes in EMGs support the predictions made by studies of instantaneous leg kinematic phase and frequency that suggest alterations to the animals’ neural oscillators.