Mechanisms of motor learning mediated by synaptic plasticity in rat primary motor cortex

Motor skill training induces long-term potentiation (LTP) and structural plasticity at dendritic spines in the primary motor cortex (M1). However, little is known about the plasticity of individual M1 neurons. Skilled motor coordination in rodents was recently assessed in studies using an accelerated rotor rod task with 1-2 days of training. Using this model, we investigated the effects of motor training on both AMPA receptor-mediated excitatory synapses and GABAA receptor-mediated inhibitory synapses in layer II/III neurons in the M1. One day of the motor training strengthened AMPA receptor-mediated excitatory synapses and drastically reduced presynaptic GABA release probability. Two days of the training further strengthened AMPA receptor-mediated excitatory synapses as well as NMDA receptors, and increased presynaptic glutamate release while also restoring presynaptic GABA release probability. In this review, we discuss the dynamic changes observed in both glutamatergic and GABAergic plasticity as well as intrinsic plasticity after the training.