Scientists at Stanford University have uncovered a mechanism for the formation of motor memories, in which motor engrams are formed in the brain – distributed neural networks, the repeated activation of which is associated with the reproduction of a learned skill. The results of the study, published in the journal Neuron, may help uncover the underlying causes of disorders such as Parkinson’s disease.
Memories are thought to be encoded in the brain as active networks of hundreds or thousands of neurons, sometimes distributed to distant regions of the brain. Previous research shows that certain forms of learning activate certain neurons that fire again when learned memories are recalled. These patterns are called memory engrams, but it has not yet been known whether such networks form when motor skills are learned.
During the experiment, scientists taught mice to get food pellets through a small slot. In this case, neurons in the motor cortex of the brain were identified, which were activated during the learning process. Potential engrams were tagged with a fluorescent marker to determine if they would be triggered later when the skill was played.
It turned out that the mice that memorized the skill showed increased activity in the same neurons that were first identified during the learning period. This proves that it is these neurons that are responsible for the encoding of skills, which occurs through the formation of new synaptic inputs in the motor cortex and outputs in the dorsolateral striatum.
Evidence suggests that motor memories are not only dispersed in the brain, but also highly redundant. By repeating and improving learned skills, a person constantly strengthens motor engrams, creating new connections. The neurotransmitter reward system involving dopamine can also influence the persistence of motor memory. It is currently believed that Parkinson’s disease is the result of a blockage of motor engrams, however, in this case, motor skills could be practiced and strengthened. If the disease destroys engrams and prevents the formation of new ones, then another approach must be used for effective treatment.