Feedback regulation of temporal muscle activation patterns for postural control before and after peripheral neuropathy
Introduction: Neural mechanislllS determining temporal pattcl1ls of muscle activity during poshlral responses are not understood. Fulluwing pyridoxine inuuced somatosensory loss in cats, unset latencies of automatic poshu-al responses are delayed, and balance is impaired. We introduce a new method for correlating temporal patterns of muscle activation with task-level variahles in the context of postural responses to perturbation. Methods: We measured postmal responses to support smface tronslations before and after loss of group I afferents indnced by pyridoxine intoxication. We reconstructed temporal EMG patterns llsing a feedback loop with delays, on CoM acceleration. velocity, and displacement. Resnlts: Prior to lesion, temporal EMG pattems were well reconstructed using delayed feedback on CoM kinematics. After neuropathy, the delay ill postural response latency was attributed to a loss of accderation feedback. A compensatOlY increase in velocity feedback was also observed Discussion: feedback on CoM acceleration is necessaty for normal posmral latencies associated with balance control. The sensory infonllation related to acceleration is encoded in group I sensory afferents. Conclnsion: Dynamics of high-level task variables detenlline temporal EMG patterns for poshlral control. Loss of large diameter proprioceptive afferents disrupts acceleration feedback.