[초청강연] Motor Skill is created and maintained by various brain areas and various information

Motor Skill is created and maintained by various brain areas and various information
Motor Skill is important for us (humans) and many animals to improve their lives. Then, how
can the brain learn and keep Motor Skill? We thus generated a behavioral task in which the
subject needs to learn a particular sequence of hand movement. Based on this method, each
subject can learn many sequences (e.g., 10) for each hand (left, right). We found that all objects
(monkeys or humans) improve across trials as well as across days (e.g., 1 year).
During learning the performance improved across trials in 2 ways. At each step the subject
needs to choose 1 or 2 objects, which was improved across trials (Accuracy). In addition, the
choice of the object became quicker across days (Speed). After long-term learning, the object
choice occurred before the object appeared (based on the prediction of the upcoming object).
This occurred by eye movement (saccade) followed by hand movement. These data suggest
that Motor Skill is maintained by Sequential Memory (e.g., sequential positions of many
objects).
We then examined how the learned Motor skill is maintained by stopping the procedure for
more than 1 year. Then, both Accuracy and Speed were maintained (= still skillful) in monkeys
and humans. In humans, the maintained Motor Skill tends not be remembered. In monkeys,
even when they used the opposite hand, Accuracy (not Speed) was maintained. This suggests
that the learning by eye movement alone can make the behavior accurate.
Based on this Motor Skill task, we studied the neuronal activity and its function in various
brain areas using fMRI in humans and neuronal recording/inhibition in monkeys. We found that
various areas in the cerebral cortex, basal ganglia, and cerebellum are active sequentially or
simultaneously. The interaction between cerebral cortex and basal ganglia mainly controls
Choice (e.g., which position, object, action). In contrast, the interaction between cerebral
cortex and cerebellum controls Time (e.g., when). In addition, each of the areas (cerebral
cortex, basal ganglia, cerebellum) is basically separated to two groups: Voluntary (based on
Short-term Memory) and Automatic (based on Long-term Memory).