A new conditioning paradigm: conditioned limb movements in locomoting decerebrate ferrets.

These experiments address the hypothesis that the trajectory of a forelimb in decerebrate ambulating ferrets can be conditioned to avoid an obstacle encountered during the locomotor cycle. The perturbation was produced by interjecting a bar into the trajectory of the forelimb during swing phase. Over 5-15 steps the flexion of the elbow progressively increased until the forelimb was elevated over the bar. Avoiding the bar often required that the maximum height of the paw during swing phase was doubled. When the bar was no longer thrust into the trajectory of the forelimb, the conditioned behavior persisted for several step cycles. The results indicate that decerebrate ferrets are capable of acquiring a conditioned limb movement that is not a typical conditioned reflex but rather an accentuation of a component of the step cycle performed to avoid an interruption of swing phase.