Activity-dependent synaptic dynamics in motor circuits of the spinal cord

In this article, we describe the most relevant recent research studies on the capability of spinal motor synapses to potentiate or depress their connectivity strength depending on their previous activity, termed activity-dependent synaptic plasticity (ADSP). Currently, ADSP in motor spinal circuits is mainly studied in vivo , with a significant body of work conducted in humans. Here, we review recent data obtained on the modulation of the post-activation depression of the electrically induced stretch reflex (H-reflex), and describe the use of spike-timing dependent plasticity (STDP)-like stimulation protocols to improve motor function after spinal cord insults. Altogether these recent findings point to the salient role played by ADSP in motor functional recovery. However, thus far there are few available data concerning the cellular basis of the synaptic dynamics of motor spinal networks. We, therefore, believe that we need to bridge this gap to accurately establish stimulation paradigms that restore spinal synaptic dynamics and enable the improvement of motor recovery after injury.