Treadmill Stepping after Epidural Stimulation Cessation in Decerebrated Cats

Summary: It was repeatedly shown that the locomotion evoked by epidural-induced electrical stimulation can last for a certain amount of time after stimulation cessation in decerebrated and spinal animals. This so-called after-stepping reflects the maintenance level for the activation of locomotor neuronal circuitry, but only scarce information exists about after-stepping peculiarities. We provide a comparative investigation of after-stepping and stepping under epidural stimulation using electromyographic and kinematic signals as well as ground reaction forces in 16 decerebrated cats. Our principal findings are as follows: (1) the ground reaction forces decrease more after epidural stimulation cessation compared to anterior–posterior limb movements; (2) the step cycle duration is longer for after-steps; (3) the electromyographic signal of the extensor gastrocnemius lateralis muscle during after-stepping decreases faster compared to the signal from the flexors iliopsoas and tibialis anterior and to the extensor soleus muscle; and (4) electromyographic stability is reduced after epidural stimulation cessation. We suppose that different levels of the spinal central pattern generator can be differently attenuated after external trigger cessation. These data could be important for the elaboration of locomotor models and for rehabilitation techniques. New Findings: Our new findings come from comparative investigations of the so-called after-stepping (locomotion after electrical stimulation cessation) and locomotion observed during epidural-induced electrical stimulation. Our new findings are as follows: after epidural stimulation cessation, (1) the ground reaction forces decrease faster compared to anterior–posterior limb movements; (2) the electromyographic signal of the extensor gastrocnemius lateralis muscle decreases faster compared to the signals from the flexors iliopsoas and tibialis anterior and to the extensor soleus muscle; and (3) electromyographic stability is reduced.