Collaboration between two researchers at the Rappaport Faculty of Medicine reveals that local release of dopamine in the motor cortex is a key to acquiring new motor skills
One of the brain's greatest challenges is learning new motor skills, from writing to playing a musical instrument or performing complex sports movements. New research conducted by two faculties at the Technion reveals how the brain reorganizes its neuronal networks during this process, and how dopamine – a molecule best known for its links to the brain's reward system – plays a critical role in motor learning. The study, published inNature Communications. Led by Dr. Hadas Ben-Isti, Prof. Jackie Schiller, and student Amir Ganaim, who is studying in the prestigious MD/PhD track. It was attended by Prof. Ronen Talmon and student Avigail Cohen-Rimon from the Viterbi Faculty of Electrical and Computer Engineering.
The ability to acquire new motor skills is essential for the functioning of the organism and its ability to respond adaptively to sensory information in a changing environment. It is now known that motor learning is based on the activity of neuronal networks in the primary motor cortex, located in the cerebral cortex. This area is the "control center" responsible for voluntary motor actions, where the planning and execution of various movements and motor learning take place, and from here commands are sent to the various organs via the spinal cord and various motor brain centers. Using advanced tools of calcium imaging from neurons in behaving mice and chemogenetic inhibition, the researchers mapped dynamic changes in neuronal networks in the cerebral cortex during the acquisition of a motor skill. They discovered that during learning, the networks organize from a "novice" structure to an "expert" structure and that this mechanism depends on the release of the dopamine molecule locally in the motor cortex.
Normally, these molecules are “sent” to the primary motor area from another area of the brain, called the ventral tegmentum (VTA). The researchers hypothesized that this release of dopamine activates plasticity mechanisms that cause changes in the functional connectivity between neurons, thereby enabling motor learning. This change is essentially a “storage mechanism” for new skills for future use. In other words, it is a process of Learning from reinforcement, in which reinforcement (recognition of success) drives a process of structural change in the organization of neurons. To verify the essentiality of this mechanism, the researchers examined the dynamics of the network structure as well as learning itself when blocking the release of dopamine molecules to the primary motor area. The results were unequivocal: when dopamine was blocked, learning stopped completely – the mice were unable to improve their performance on the task of sending a forelimb to grasp food. At the same time, the network of neurons in the motor cortex remained “frozen” without reorganization. As soon as dopamine release was restored, learning resumed and the neural network reorganized according to the acquired skill.
These findings indicate that local dopamine release serves as an essential signal that enables neural plasticity (plasticity) in the motor cortex, thereby ensuring the adaptations required to generate precise and efficient motor commands. Another interesting finding was that the blockade had no effect on existing motor skills at all – that is, the researchers demonstrated that dopamine release is critical for learning a new movement, but is not required for performing a movement that has already been learned. This study represents another step in understanding brain plasticity and learning mechanisms at the neural level, and highlights the brain’s ability to reorganize itself to allow us to refine our motor skills throughout life. These insights may advance a deeper understanding of neurological diseases such as Parkinson’s, which impair motor learning ability.
The research was supported by the National Science Foundation, the Prince Foundation, and the Rappaport Foundation.
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