Properties of layer V pyramidal neurons in the primary motor cortex that represent acquired motor skills.

Layer V neurons in primary motor cortex (M1) are required for motor skill learning. We analyzed training-induced plasticity using a whole-cell slice patch-clamp technique with a rotor rod task, and found that training induces diverse changes in intrinsic properties and synaptic plasticity in M1 layer V neurons. Although the causal relationship between specific cellular changes and motor performance is unclear, by linking individual motor performance to cellular/synaptic functions, we identified several cellular and synaptic parameters that represent acquired motor skills. With respect to cellular properties, motor performance was positively correlated with resting membrane potential and fast afterhyperpolarization, but not with the membrane resistance, capacitance, or threshold. With respect to synaptic function, the performance was positively correlated with AMPA receptor-mediated postsynaptic currents, but not with GABA receptor-mediated postsynaptic currents. With respect to live imaging analysis in Thy1-YFP mice, we further demonstrated a cross-correlation between motor performance, spine head volume, and self-entropy per spine. In the present study, we identified several changes in M1 layer V pyramidal neurons after motor training that represent acquired motor skills. Furthermore, training increased extracellular acetylcholine levels known to promote synaptic plasticity, which is correlated with individual motor performance. These results suggest that systematic control of specific intracellular parameters and enhancement of synaptic plasticity in M1 layer V neurons may be useful for improving motor skills.