Motor learning

Motor learning is the process of improving the motor skills, the smoothness and accuracy of movements. It is obviously necessary for complicated movements such as speaking, playing the piano and climbing trees, but it is also important for calibrating simple movements like reflexes, as parameters of the body and environment change over time. The cerebellum and basal ganglia are critical for motor learning.

As a result of the universal need for properly calibrated movement, it is not surprising that the cerebellum and basal ganglia are widely conserved across vertebrates from fish to humans.

Although motor learning is capable of achieving very skilled behavior, much has been learned from studies of simple behaviors. These behaviors include eyeblink conditioning, motor learning in the vestibulo-ocular reflex, and birdsong. Research on Aplysia californica, the sea slug, has yielded detailed knowledge of the cellular mechanisms of a simple form of learning.

An interesting type of motor learning occurs during operation of a brain-computer interface. For example, Mikhail Lebedev, Miguel Nicolelis and their colleagues recently demonstrated cortical plasticity that resulted in incorporation of an external actuator controlled through a brain-machine interface into the subject's neural representation.

At a cellular level, motor learning manifests itself in the neurons of the motor cortex. Using single-cell recording techniques, Dr. Emilio Bizzi and his collaborators have shown the behavior of certain cells, known as “memory cells,” can undergoing lasting alteration with practice.

Motor learning is also accomplished on the musculoskeletal level. Each motor neuron in the body innervates one or more muscle cells, and together these cells form what is known as a motor unit. For a person to perform even the simplest motor task, the activity of thousands of these motor units must be coordinated. It appears that the body handles this challenge by organizing motor units into modules of units whose activity is correlated.