Plasticity of the motor cortex:focusing on the role of dopamine innervation

YUNG Wing-Ho

（School of Biomedical Sciences，F(xiàn)aculty of Medicine& Gerald Choa Neuroscience Center，The Chinese Univer?sity of Hong Kong，Hong Kong，China）

Plasticity of the motor cortex:focusing on the role of dopamine innervation

YUNG Wing-Ho

（School of Biomedical Sciences，F(xiàn)aculty of Medicine& Gerald Choa Neuroscience Center，The Chinese Univer?sity of Hong Kong，Hong Kong，China）

The motor cortex plays a key role in motor con?trol as its output directly generates movement.However，it is known that the motor cortex also exhibits a high degree of plasticity that may be important in both health and disease.Here I provide evidence to support that dopami?nergic innervation arising from the midbrain plays critical roles in the process of acquiring novel motor skills as well as recovery of motor functions after ischemic stroke. Based on extracellular multi-unit recordings from conscious freely moving rats，we investigated the dynamics of neu?rons in the output layer 5b（L5b）of the primary motor cortex during the training of a forelimb reaching for food task.We found a subpopulation of task-recruited layer 5b neurons that not only became more movement-encoding during motor learning，but their activities were also more temporally aligned to motor execution.These phenomena were accompanied by the emergence of reproducibleneurodynamics of the L5b neuronal ensemble and traininginduced long-term synaptic plasticity of inputs to these neurons，but were highly disrupted by local denervation ofdopaminergic inputs originating from the ventral tegmental area.In another series of experiments based on rodent models of focal ischemic stroke，administra?tion of L-DOPA，the precursor of dopamine，significantly promoted motor function recovery.Morphological and biochemicalexamination ofthe perilesioned area provided evidence that neuroplasticity markers，dendritic arborisation and synaptic plasticity were increased by the treatment.Furtherexamination ofneuronalactivity throughin vivorecording revealed that motor cortical regions adjacent to the infarct had restored capability for synaptic plasticity.Finally，pharmacological blockade of either D1 or D2 receptors at the perilesioned region abolished the beneficial effects.Together，our findings highlight the importance of the plasticity of the motor cortex in health and disease that are mediated by the mesocortical dopaminergic pathway.

Foundation item：The project supported by NSFC grant（SZRIA0314025）；SRFDP-HKRGC grant（2900703）；HKGRF grant（2140903）；and HMRF grant（02130976）