モータ制御入門

Motor control operates through a hierarchical nervous system structure. The motor cortex, consisting of premotor and primary motor areas, sits at the top and projects upper motor neurons down the spinal cord. The cerebellum fine-tunes locomotion aspects like rhythm and balance, while the basal ganglia selects which motion to execute. Lower levels include the brainstem and spinal cord, which handle involuntary reflexes and coordinate movement execution.

The primary motor area contains a motor map where neurons controlling specific body parts are localized to the same regions. This spatial organization can be represented as a cortical homunculus, a distorted map of the body reflecting the relative amount of motor cortex devoted to each body part. The premotor area, located anterior to the primary motor area, controls task-specific complex movements and plays a major role in motor planning and learning.

The cerebellum uses sensory information to fine-tune locomotion aspects such as rhythm, gait, balance, and posture, and contributes to motor planning and learning. The basal ganglia, rich in connections to the cortex, selects which motion to execute from multiple options. Damage to the basal ganglia causes major motor diseases like Parkinson's and Huntington's, highlighting their importance in motor function.

Scientists investigate how sensory perceptions influence movements, including effects of visual illusions and different perspectives on voluntary and involuntary motions. They study balance, coordination, and dexterity while pinpointing pathological events in movement disorders. Motor skill acquisition is also examined, focusing on the time and feedback required to learn skills and how permanent learned skills become. These questions help develop better treatments for motor disorders.

Rodents undergo various behavioral tests to evaluate motor function. Basic locomotor function is assessed using treadmill exercises or open-field activities. Balance and coordination are tested with balance beam and rotarod setups. Motor learning is investigated through reaching tasks for food rewards, while food handling tasks assess forelimb dexterity. These tests can be combined with interventions like drug administration or surgery to link motor activities to specific neurological bases.

Live-cell imaging, electroencephalography (EEG), and electromyography (EMG) measure neuronal and muscle activities while subjects perform motor tasks. EEG records brain electrical activity, while EMG captures muscle electrical signals. These techniques can be combined with behavioral tests and interventions to observe neurological changes during movement. Multi-modal data collection using EEG, EMG, and motion-capture protocols provides a comprehensive picture of motor control mechanisms.

Researchers induce cervical spinal cord injuries in rats and test effects on limb-use during locomotion and food handling tasks. These experiments help scientists understand the role of specific neural circuits in limb motor activity. By combining behavioral tests with surgically induced injuries, researchers can establish direct links between particular neural lesions and resulting motor deficits, advancing understanding of motor control mechanisms.